oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Application of Neuro-Wavelet Algorithm in Ultrasonic-Phased Array Nondestructive Testing of Polyethylene Pipelines  [PDF]
Reza Bohlouli,Babak Rostami,Jafar Keighobadi
Journal of Control Science and Engineering , 2012, DOI: 10.1155/2012/389690
Abstract: Polyethylene (PE) pipelines with electrofusion (EF) joining is an essential method of transportation of gas energy. EF joints are weak points for leakage and therefore, Nondestructive testing (NDT) methods including ultrasonic array technology are necessary. This paper presents a practical NDT method of fusion joints of polyethylene piping using intelligent ultrasonic image processing techniques. In the proposed method, to detect the defects of electrofusion joints, the NDT is applied based on an ANN-Wavelet method as a digital image processing technique. The proposed approach includes four steps. First an ultrasonic-phased array technique is used to provide real time images of high resolution. In the second step, the images are preprocessed by digital image processing techniques for noise reduction and detection of ROI (Region of Interest). Furthermore, to make more improvement on the images, mathematical morphology techniques such as dilation and erosion are applied. In the 3rd step, a wavelet transform is used to develop a feature vector containing 3-dimensional information on various types of defects. In the final step, all the feature vectors are classified through a backpropagation-based ANN algorithm. The obtained results show that the proposed algorithms are highly reliable and also precise for NDT monitoring. 1. Introduction The ultrasonic technique as a nondestructive testing (NDT) method has been widely used over decades to evaluate the quality of materials and equipments without causing damage in a large range of industries. In the evaluation of pressure vessels and piping, not only is UT utilized in manufacturing quality controlling, but also has been used in service monitoring and residual life prediction, such as the inspection of welded joints, monitoring of crack propagation, and evaluation of materials property deterioration. In the specific case of welded materials, the research for the development of an acceptable system for analyzing the extracted images from the welded joints has grown considerably in the last years [1–4]. One of its applications is in the gas pipelines where the usage of natural gas in residential, commercial, and industrial facilities is increased day by day. In this way, Polyethylene pipes rapidly substituted the metal pipes, because the polyethylene pipes have a high-corrosion resistance, easy to form, lighter, and cheaper than metal ones. In fact, the main reason for using PE pipes in gas distribution is that its material has a high-chemical resistance against corrosive materials in transported gas. In
Engine Oil Condition Monitoring Using High Temperature Integrated Ultrasonic Transducers
Kuo-Ting Wu,Makiko Kobayashi,Zhigang Sun,Cheng-Kuei Jen
International Journal of Prognostics and Health Management , 2011,
Abstract: The present work contains two parts. In the first part, high temperature integrated ultrasonic transducers (IUTs) made of thick piezoelectric composite films, were coated directly onto lubricant oil supply and sump lines of a modified CF700 turbojet engine. These piezoelectric films were fabricated using a sol-gel spray technology. By operating these IUTs in transmission mode, the amplitude and velocity of transmitted ultrasonic waves across the flow channel of the lubricant oil in supply and sump lines were measured during engine operation. Results have shown that the amplitude of the ultrasonic waves is sensitive to the presence of air bubbles in the oil and that the ultrasound velocity is linearly dependent on oil temperature. In the second part of the work, the sensitivity of ultrasound to engine lubricant oil degradation was investigated by using an ultrasonically equipped and thermally-controlled laboratory testing cell and lubricant oils of different grades. The results have shown that at a given temperature, ultrasound velocity decreases with a decrease in oil viscosity. Based on the results obtained in both parts of the study, ultrasound velocity measurement is proposed for monitoring oil degradation and transient oil temperature variation, whereas ultrasound amplitude measurement is proposed for monitoring air bubble content.
Ultrasonic Periodontal Probing Based on the Dynamic Wavelet Fingerprint  [cached]
Jidong Hou,S. Timothy Rose,Mark K. Hinders
EURASIP Journal on Advances in Signal Processing , 2005, DOI: 10.1155/asp.2005.1137
Abstract: Manual pocket depth probing has been widely used as a retrospective diagnosis method in periodontics. However, numerous studies have questioned its ability to accurately measure the anatomic pocket depth. In this paper, an ultrasonic periodontal probing method is described, which involves using a hollow water-filled probe to focus a narrow beam of ultrasound energy into and out of the periodontal pocket, followed by automatic processing of pulse-echo signals to obtain the periodontal pocket depth. The signal processing algorithm consists of three steps: peak detection/characterization, peak classification, and peak identification. A dynamic wavelet fingerprint (DWFP) technique is first applied to detect suspected scatterers in the A-scan signal and generate a two-dimensional black and white pattern to characterize the local transient signal corresponding to each scatterer. These DWFP patterns are then classified by a two-dimensional FFT procedure and mapped to an inclination index curve. The location of the pocket bottom was identified as the third broad peak in the inclination index curve. The algorithm is tested on full-mouth probing data from two sequential visits of 14 patients. Its performance is evaluated by comparing ultrasonic probing results with that of full-mouth manual probing at the same sites, which is taken as the ¢ € gold standard. ¢ €
Ultrasonic Rangefinder Spikes Rejection Using Discrete Wavelet Transform: Application to UAV  [PDF]
Ayman El-Badawy, Ramy Rashad
Journal of Sensor Technology (JST) , 2015, DOI: 10.4236/jst.2015.52005
Abstract: This paper presents a spikes removing methodology for ultrasonic rangefinders with an application to a quadrotor unmanned aerial vehicle. Ultrasonic sensors suffer from spikes in distance measurements due to specular reflectance and acoustic noise. Removing these spikes is necessary for improving the hovering performance of the quadrotor. The spikes removing algorithm is based on the discrete wavelet transform. The algorithm is implemented in simulation to study the effect of the altitude measurement spikes on the control performance of the quadrotor with and without the algorithm. The algorithm is also implemented digitally on ultrasonic measurements from a real flight. Results show that the method is capable of rejecting the spikes in the measurements efficiently leaving the altitude control signal unaffected.
Ultrasonic NDE Techniques for Impact Damage Inspection on CFRP Laminates  [cached]
Qin Shen,Mohammed Omar,Shan Dongri
Journal of Materials Science Research , 2012, DOI: 10.5539/jmsr.v1n1p2
Abstract: This study investigates the different types of ultrasonic inspection, when applied to assess the impact damage in Carbon Fiber Reinforced Plastic CFRP laminates. The study surveys the two most used ultrasonic testing approaches first; namely the pulse-echo and the through-transmission modes. Then, the manuscript discusses and analyzes the enhanced ultrasonic testing methods that use the polar scattering, the thickness independent techniques, air-coupled, and the techniques based on the Ultrasonic Rayleigh and Lamb Waves. Additionally, presented study demonstrates some of these techniques to test a CFRP sample with embedded defects, along with the processing required for the acquired results such as the wavelet transformation.
Wavelet-based deconvolution of ultrasonic signals in nondestructive evaluation  [PDF]
Roberto Henry Herrera,Rubén Orozco,Manuel Rodríguez
Computer Science , 2012,
Abstract: In this paper, the inverse problem of reconstructing reflectivity function of a medium is examined within a blind deconvolution framework. The ultrasound pulse is estimated using higher-order statistics, and Wiener filter is used to obtain the ultrasonic reflectivity function through wavelet-based models. A new approach to the parameter estimation of the inverse filtering step is proposed in the nondestructive evaluation field, which is based on the theory of Fourier-Wavelet regularized deconvolution (ForWaRD). This new approach can be viewed as a solution to the open problem of adaptation of the ForWaRD framework to perform the convolution kernel estimation and deconvolution interdependently. The results indicate stable solutions of the estimated pulse and an improvement in the radio-frequency (RF) signal taking into account its signal-to-noise ratio (SNR) and axial resolution. Simulations and experiments showed that the proposed approach can provide robust and optimal estimates of the reflectivity function.
A Comparative Study of Scheduling Techniques for Multimedia Applications on SIMD Pipelines  [PDF]
Mehmet Ali Arslan,Flavius Gruian,Krzysztof Kuchcinski
Computer Science , 2015,
Abstract: Parallel architectures are essential in order to take advantage of the parallelism inherent in streaming applications. One particular branch of these employ hardware SIMD pipelines. In this paper, we analyse several scheduling techniques, namely ad hoc overlapped execution, modulo scheduling and modulo scheduling with unrolling, all of which aim to efficiently utilize the special architecture design. Our investigation focuses on improving throughput while analysing other metrics that are important for streaming applications, such as register pressure, buffer sizes and code size. Through experiments conducted on several media benchmarks, we present and discuss trade-offs involved when selecting any one of these scheduling techniques.
Advances in Asset Management Techniques: An Overview of Corrosion Mechanisms and Mitigation Strategies for Oil and Gas Pipelines  [PDF]
Chinedu I. Ossai
ISRN Corrosion , 2012, DOI: 10.5402/2012/570143
Abstract: Effective management of assets in the oil and gas industry is vital in ensuring equipment availability, increased output, reduced maintenance cost, and minimal nonproductive time (NPT). Due to the high cost of assets used in oil and gas production, there is a need to enhance performance through good assets management techniques. This involves the minimization of NPT which accounts for about 20–30% of operation time needed from exploration to production. Corrosion contributes to about 25% of failures experienced in oil and gas production industry, while more than 50% of this failure is associated with sweet and sour corrosions in pipelines. This major risk in oil and gas production requires the understanding of the failure mechanism and procedures for assessment and control. For reduced pipeline failure and enhanced life cycle, corrosion experts should understand the mechanisms of corrosion, the risk assessment criteria, and mitigation strategies. This paper explores existing research in pipeline corrosion, in order to show the mechanisms, the risk assessment methodologies, and the framework for mitigation. The paper shows that corrosion in pipelines is combated at all stages of oil and gas production by incorporating field data information from previous fields into the new field’s development process. 1. Introduction The oil and gas industry is an asset intensive business with capital assets ranging from drilling rigs, offshore platforms and wells in the upstream segment, to pipeline, liquefied natural gas (LNG) terminals, and refineries in the midstream and downstream segments. These assets are complex and require enormous capital to acquire. An analysis of the five major oil and gas companies (BP, Shell, ConocoPhillips, Exxonmobil, and Total) shows that plant, property, and equipment on average accounts for 51% of the total assets with a value of over $100 billion [1]. Considering the huge investment in assets, oil and gas companies are always under immense pressure to properly manage them. To achieve this involves the use of different optimization strategies that is aimed at cost reduction and improved assets reliability [2]. Due to the growth in the demand of oil and gas around the world, companies are developing new techniques to reach new reservoirs in the offshore and onshore arena [3]. This is putting pressure on most of the facilities with the attendant cost of maintenance soaring [1]. The continuous utilization and the ageing of facilities have resulted in record failures in the oil and gas plants. Research shows that between 1980 and 2006,
REVIEW OF VARIOUS ULTRASONIC TECHNIQUES EMPLOYED IN MODERN INDUSTRIES  [PDF]
S. MUTHUMARI,,ANURAG SINGH
International Journal of Engineering Science and Technology , 2011,
Abstract: In today’s industries, various technological advancements have begun to be implemented. With more advances comes a greater risk of errors. Ultrasonic techniques are one of the most prominent methods used for error detection and improvement of efficiency. There are many variations of this technology and each one has its own application based on the need of the situation. This paper gives a review of thegeneral ultrasonic technique and aims at a comparative study of the various applications and processes involved that are currently used or could be implemented in the future. The paper also gives suggestions on the alternatives that can be used to the currently existing techniques, along with their advantages and disadvantages.
Calcium hydroxide removal: effectiveness of ultrasonic and manual techniques
B?ttcher, Daiana Elisabeth;Rahde, Nicole de Mello;Grecca, Fabiana Soares;
Revista Odonto Ciência , 2012, DOI: 10.1590/S1980-65232012000200011
Abstract: purpose: different techniques have been proposed to improve the removal of calcium hydroxide. the purpose of this in vitro study was to compare the effectiveness of ultrasound and manual techniques in the removal of calcium hydroxide from root canals. methods: thirty-eight single-rooted teeth were divided into two groups of 19 teeth each. the teeth were prepared using the crown-down technique with an apical master file #50. after shaping, the canals were radiographed and dressed with calcium hydroxide. after 14 days, the calcium hydroxide was removed with the ultrasound technique in group i and through manual filing in group ii. the teeth were then radiographed again to evaluate the removal of the paste. to assess the calcium hydroxide removal, the radiographs were scanned and analyzed based on the gray levels. the independent samples and student's t-tests (α=0.05) were used for each group to compare the efficacy of calcium hydroxide removal between the groups and among thirds (cervical, middle and apical). results: there was no difference between ultrasound and manual techniques in the removal of calcium hydroxide from root canals. there were no statistical differences among the thirds analyzed. conclusion: neither manual nor ultrasonic techniques completely removed calcium hydroxide from the root canal.
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.