Mohd Hafiz Fazalul Rahiman

Ultrasonic Transmission-Mode Tomography Imaging for Liquid/Gas Two-Phase Flow

This paper details the development of noninvasive ultrasonic tomography for imaging liquid and gas flow. The transmission-mode approach has been used for sensing the liquid/gas two-phase flow, which is a kind of strongly inhomogeneous medium. Sixteen pairs of ultrasonic sensors have been used. By using low excitation voltage of 20 V, fan-shaped beam ultrasonic transmitters will emit ultrasonic pulses to the receivers. The investigations were based on the transmission and the reception of ultrasonic sensors that were mounted circularly on the surface of the experimental vessel. The algorithms used to reconstruct the concentration profile for two-phase flow using a fan-shaped beam scanning geometry were presented. By using a hybrid-binary reconstruction algorithm, real-time ultrasonic transmission-mode tomography has been developed. Experiments show that performance is acceptable with an image-reconstruction speed of 10 frames/s. The results of the experiments and possible future improvements were also discussed

Advancements in Transmitters and Sensors for Biological Tissue Imaging in Magnetic Induction Tomography

Magnetic Induction Tomography (MIT), which is also known as Electromagnetic Tomography (EMT) or Mutual Inductance Tomography, is among the imaging modalities of interest to many researchers around the world. This noninvasive modality applies an electromagnetic field and is sensitive to all three passive electromagnetic properties of a material that are conductivity, permittivity and permeability. MIT is categorized under the passive imaging family with an electrodeless technique through the use of excitation coils to induce an electromagnetic field in the material, which is then measured at the receiving side by sensors. The aim of this review is to discuss the challenges of the MIT technique and summarize the recent advancements in the transmitters and sensors, with a focus on applications in biological tissue imaging. It is hoped that this review will provide some valuable information on the MIT for those who have interest in this modality. The need of this knowledge may speed up the process of adopted of MIT as a medical imaging technology.

The Front-End Hardware Design Issue in Ultrasonic Tomography

This paper explains the front-end hardware design for ultrasonic tomography. The ultrasonic tomography system presented in this paper uses a noninvasive sensing technique with transmission-mode approach for investigating gas bubbles in an experimental column. Several explanations regarding the common tomography technique and the hardware preparation are also discussed. The sensory parts consist of 32 units of ultrasonic transceivers to form the fan-shaped beam projections. A low voltage of 20 V has been used to generate the ultrasonic burst tones. The electronic circuitry details, including the signal generator, the signal conditioning, and the signal acquisition strategy, are also presented. The results from this paper are useful for further development in ultrasonic tomography design.

Hardware Implementation of Multiple Fan Beam Projection Technique in Optical Fibre Process Tomography

The main objective of this project is to implement the multiple fan beam projection technique using optical fibre sensors with the aim to achieve a high data acquisition rate. Multiple fan beam projection technique here is defined as allowing more than one emitter to transmit light at the same time using the switch-mode fan beam method. For the thirty-two pairs of sensors used, the 2-projection technique and 4-projection technique are being investigated. Sixteen sets of projections will complete one frame of light emission for the 2-projection technique while eight sets of projection will complete one frame of light emission for the 4-projection technique. In order to facilitate data acquisition process, PIC microcontroller and the sample and hold circuit are being used. This paper summarizes the hardware configuration and design for this project.

Segmented Capacitance Tomography Electrodes: A Design and Experimental Verifications

A segmented capacitance tomography system for real-time imaging of multiphase flows is developed and presented in this work. The earlier research shows that the electrical tomography (ECT) system is applicable in flow visualization (image reconstruction). The acquired concentration profile obtained from capacitance measurements able to imaged liquid and gas mixture in pipelines meanwhile the system development is designed to attach on a vessel. The electrode plates which act as the sensor previously has been assembled and fixed on the pipeline, thus it causes obscurity for the production to have any new process installation in the future. Therefore, a segmented electrode sensor offers a new design and idea on ECT system which is portable to be assembled in different diameter sizes of pipeline, and it is flexible to apply in any number due to different size of pipeline without the need of redesigning the sensing module. The new approach of this sensing module contains the integration intelligent electrode sensing circuit on every each of electrode sensors. A microcontroller unit and data acquisition (DAQ) system has been integrated on the electrode sensing circuit and USB technology was applied into the data acquisition system making the sensor able to work independently. Other than that the driven guard that usually placed between adjacent measuring electrodes and earth screen has been embedded on the segmented electrode sensor plates. This eliminates the cable noise and the electrode, so the signal conditioning board can be expanded according to pipe diameter.

Novel Adjacent Criterion Method for Improving Ultrasonic Imaging Spatial Resolution

In this letter, we present a novel approach for improving spatial resolution in ultrasonic tomography. The proposed technique modifies a Back-projection (BP) algorithm in reconstructing tomography images. We used 32-ultrasonic transducer on a liquid column to perform the imaging process. Two phantoms were used to evaluate the proposed technique and compared with BP technique. The results showed that the proposed technique improves the spatial resolution and exhibits more accurate tomograms.

Ultrasonic process tomographic imaging sensor: An approach utilising transceivers method

Direct analysis of the internal characteristics of process plant has become a widespread need in order to improve the design and operation of the equipment especially in liquid/gas two phase flows. The applications of tomography techniques as a robust non-invasive tool for direct analysis of the characteristics of multiphase flows have increased. One of the famous real time techniques that are usually applied was ultrasonic tomography. In this study, ultrasonic tomographic imaging sensor has been utilised to visualize the distribution of liquid/gas in a vertical column. The sensing element consists of 32 units of ultrasonic transceivers to cover the pipe cross-section. The motivation of the paper is to analyse the performance of the transceiver methods in visualising bubble hold-ups in vertical column. Some analyses have been carried out using several phantoms and the system was found excellent in visualizing the internal characteristics and provides the concentration profile for the corresponding phantoms.

Detection of small gas bubble using ultrasonic transmission-mode tomography system

This paper presents the development of an ultrasonic transmission-mode tomography system for the detection of small gas bubble using higher frequency ultrasonic sensors. The selection of the sensors is important and must be suitable to the application design. Consideration on the natural limitation of ultrasonic wave is also noted as the higher the frequency of the ultrasonic transducer, the better the sensitivity but lower penetration depth. 16-pairs of these ultrasonic sensors are installed and fixed inside a sensor jig which is designed to hold all the sensors. The sensor jig is also mounted on the circumference of a vertical column which will be used as the investigated process vessel. The developments presented also include the non-invasive fabrication techniques, the electronic measurement circuits, image reconstruction technique, and finally on the imaging results of the proposed system.

Image reconstruction of a charge coupled device based optical tomographic instrumentation system for particle sizing.

This research investigates the use of charge coupled device (abbreviated as CCD) linear image sensors in an optical tomographic instrumentation system used for sizing particles. The measurement system, consisting of four CCD linear image sensors are configured around an octagonal shaped flow pipe for a four projections system is explained. The four linear image sensors provide 2,048 pixel imaging with a pixel size of 14 micron × 14 micron, hence constituting a high-resolution system. Image reconstruction for a four-projection optical tomography system is also discussed, where a simple optical model is used to relate attenuation due to variations in optical density, [R], within the measurement section. Expressed in matrix form this represents the forward problem in tomography [S] [R] = [M]. In practice, measurements [M] are used to estimate the optical density distribution by solving the inverse problem [R] = [S]−1[M]. Direct inversion of the sensitivity matrix, [S], is not possible and two approximations are considered and compared—the transpose and the pseudo inverse sensitivity matrices.

Design and Development of Ultrasonic Process Tomography

Real-time reconstruction of the flow image is needed in order to estimate the flow regime when it is continuously evolving. This flow image is important in many areas of industry, and scientific research concerning liquid/gas two-phase flow. The operation efficiency of such a process is closely related to accurate measurement, and control of hydrodynamic parameters such as flow regime, and flow rate (Rahiman et al., 2010). Commonly, the monitoring in the process industry is limited to either visual inspection or a single-point product sampling assuming the product is uniformed. This approach for the determination of fluid flow parameters of two-component flow is also known as flow imaging.