Gas leak locating in steel pipe using wavelet transform and cross-correlation method

Pipelines leakage in power plant, petrochemical complexes, and refineries can lead to explosion, pollution, and severe physical damages, so precise and on time leak locating is very important. There are many techniques for detecting and locating the leakage. In this research, we represent the leak locating principle in pressurized gas pipelines by using acoustic emission theory. An algorithm for finding the location of continuous acoustic waves resulted from leakage is provided by MATLAB software. The used leak locating technique is a combination of wavelet transform, filtering, and cross-correlation methods. The resulted acoustic emission signals were analyzed into high and low frequencies by wavelet transform and available noises on them were omitted completely by filtering. Then de-noised acoustic emission signals were reconstructed. Time differences of de-noised waves were calculated precisely by using cross-correlation function. For studying the accuracy of used method, acoustic emission testing was done by continuous leakage source. The resulted signals of leakage were recorded by two acoustic sensors in two sides of leakage source, and time difference and leak location were calculated by using the algorithm. Several tests were done by changing sensor distance from leakage source and error percent of less than 3 % was resulted in leak locating that indicated high precision of used algorithm.     

Modeling Acoustic Emission Signals Caused by Leakage in Pressurized Gas Pipe

Leakage in high pressure pipes creates stress waves which transmitted through the pipe wall. These waves can be recorded by using acoustic sensor or accelerometer installed on the pipe wall. Knowing how these waves vibrate pipe is very important in continuous leak source locating process. In this paper the pipe radial displacement caused by acoustic emission due to leakage is modeled analytically. The standard form of Donnell’s nonlinear cylindrical shell theory is used to derive the motion equation of the pipe for simply supported boundary condition. Using Galerkin method, the motion equation has been solved and a system of nonlinear equations with 7 degrees of freedom is obtained. A MATLAB code according to Runge-Kutta numerical method is generated to solve these equations and derive the pipe radial displacement. To check the theoretical results, acoustic emission testing with continuous leak source and linear array of two sensors positioned on two sides of the leakage source were carried out. The major noise of recorded signals was removed through the wavelet transform and filtering technique. For better analysis, fast Fourier transform (FFT) was taken from theoretical and de-noised experimental results. Comparing the results showed that the frequency which carried the most amount of energy is the same that expresses excellent agreement between the theoretical and experimental results validating the analytical model.     

Speed limit reduction in urban areas: A before–after study using Bayesian generalized mixed linear models

In fall 2009, a new speed limit of 40 km/h was introduced on local streets in Montreal (previous speed limit: 50 km/h). This paper proposes a methodology to efficiently estimate the effect of such reduction on speeding behaviors. We employ a full Bayes before–after approach, which overcomes the limitations of the empirical Bayes method. The proposed methodology allows for the analysis of speed data using hourly observations. Therefore, the entire daily profile of speed is considered. Furthermore, it accounts for the entire distribution of speed in contrast to the traditional approach of considering only a point estimate such as 85th percentile speed. Different reference speeds were used to examine variations in the treatment effectiveness in terms of speeding rate and frequency. In addition to comparing rates of vehicles exceeding reference speeds of 40 km/h and 50 km/h (speeding), we verified how the implemented treatment affected “excessive speeding” behaviors (exceeding 80 km/h). To model operating speeds, two Bayesian generalized mixed linear models were utilized. These models have the advantage of addressing the heterogeneity problem in observations and efficiently capturing potential intra-site correlations. A variety of site characteristics, temporal variables, and environmental factors were considered. The analyses indicated that variables such as lane width and night hour had an increasing effect on speeding. Conversely, roadside parking had a decreasing effect on speeding. One-way and lane width had an increasing effect on excessive speeding, whereas evening hour had a decreasing effect. This study concluded that although the treatment was effective with respect to speed references of 40 km/h and 50 km/h, its effectiveness was not significant with respect to excessive speeding-which carries a great risk to pedestrians and cyclists in urban areas. Therefore, caution must be taken in drawing conclusions about the effectiveness of speed limit reduction. This study also points out the importance of using a comparison group to capture underlying trends caused by unknown factors.     

A Multiband Inductor-Reuse CMOS Low-Noise Amplifier

This paper presents the design and implementation of a new multiband, multistandard CMOS low-noise amplifier (LNA) that reuses inductors for different frequency bands to minimize chip area. The idea is to adaptively reconfigure a CMOS transistor in either common source or common gate configuration to achieve narrow-band (NB) or wide-band (WB) input matching, respectively, while conveniently reusing input and load inductors for both bands. This architecture is suitable for 802.11 a/b/g and Public Safety Broadband (PSB) applications, where the NB configuration covers wireless local area network (WLAN) 802.11 b/g, while the WB configuration accommodates the PSB at 4.9 GHz and WLAN 802.11 a. Two versions of the proposed idea, a tapped-capacitor and a tapped-inductor input-matched LNA, have each been designed and fabricated in 0.13-mum CMOS and measurement results are demonstrated.     

Exploring deep insights into the interaction mechanism of a quinazoline derivative with mild steel in HCl: electrochemical,DFT, and molecular dynamic simulation studies

A novel quinazoline derivative, 3-cyclopropyl-3,4-dihydroquinoline-2(1H)-One (CPHQ), was successfully designed and synthesized. Then, its corrosion inhibition behavior on carbon steel (CS) surface in 1.0?M HCl at different temperatures was investigated using chemical, electrochemical and theoretical techniques. The experiments confirmed that the studied inhibitor shows inhibition efficiency as high as 95% even at very low concentration of 5?×?10^?3 M. To ascertain the nature of adsorption of CPHQ molecules on CS surface, Langmuir adsorption isotherm model was best fitted. From potentiodynamic polarization (PDP) calculations, it was concluded that the CPHQ acted as a mixed type corrosion inhibitor. Electrochemical impedance spectroscopy (EIS) studies revealed that increase in CPHQ concentration, resulted in an increase in the polarization resistance with a simultaneous decrease in the double-layer capacitance values. PDP tests were also performed to understand the corrosion behavior of CS as a function of temperature without and with varying concentrations of CPHQ, at temperatures 303, 313, 323, and 333?K. It can be concluded that the corrosion inhibition effect was dependent on the concentration of the inhibitor and the solution temperature. In order to understand the basic insights of the action mode of CPHQ molecules, Density Functional Theory (DFT) method, and Molecular Dynamic (MD) simulations were also employed on the optimized structure of CPHQ.     

Novel numerical solutions of nonlinear heat transfer problems using the linear barycentric rational interpolation

In this investigation, a numerical technique to obtain the approximate solutions of four well‐known nonlinear differential equations in the area of heat transfer is presented. This method is based on the operational matrix of derivative of linear barycentric rational interpolation. The main advantages of this approach are that it uses the Floater‐Hormann weights, which are very efficient in practice, and reduces the governing differential equation to a system of algebraic equations. The results are compared with the obtained numerical results of the fourth‐order Runge‐Kutta method along with the shooting method and some of the previously existing methods. The acquired results reveal that the derivative operational matrix method with barycentric rational basis functions is very efficient and can be implemented easily and fast.