Wang Huaxiang

Two methods for measurement of gas-liquid flows in vertical upward pipe using dual-plane ERT system

In modern industrial processes, the accurate measurement of two-phase flow is an important task. Process tomography can provide a distribution information of a two-phase pipe flow. In order to carry out instantaneous flowrate measurements of the gas-liquid two-phase flow in a vertical upward pipe, a dual-plane electrical-resistance-tomography (ERT) system is combined with a cross-correlation technique to measure the gas-liquid two-phase flow, in which the continuous phase is a conductive liquid. A pixel correlation method and a feature-value-correlation method are applied to estimate the disperse-phase velocity. Two methods are used to estimate the local void fraction and the disperse velocity distribution by reconstructing the image pixel gray value distribution. Estimates of the mean void fraction and the disperse-phase mean velocity are obtained by extracting the feature value of the measured data at the dual-plane ERT boundary. The variation in the disperse-phase distribution with changes in time is considered, and the estimated values for both the disperse-phase void fraction and velocity have been experimentally obtained, which are used in the calculation of the instantaneous flowrate. The air-water two-phase flow experiments are designed to evaluate the validity of the two methods used in estimation. The experimental results agree with the theoretical methods for obtaining the disperse-phase velocity and instantaneous-flowrate measurement in the vertical upward pipeA dual-plane Electrical Resistance Tomography (ERT) system is employed to combine ERT with cross correlation technique to measure the gas phase volumetric flowrate in gas-liquid flows in vertical upward pipe. According to the uniformity of the local void fraction distribution and the velocity distribution of gas phase, pixel-correlation method and eigenvalue-correlation method are put forward to estimate the gas phase volumetric flowrate. This paper compares the two estimate methods and makes preliminary study of the applicability of the two methods. Two experiments were designed to evaluate the validity of those two estimate methods. Experimental results were presented to analyze their characters respectively.

Optimum design of the structure of the electrode for a medical EIT system

To study the distribution of the sensing field affected by the configuration of the compound electrodes used in the medical EIT system, a finite element model with the condition of the coercive equipotential nodes on the boundary of an object is established. The distribution of the sensing field affected by the width of the compound electrodes is analysed using the simulation method and an optimum design of the structure size of the compound electrode for various excitation strategies is obtained.

Mixing Frequency Bio-impedance Measurement Technology based on DFT and Virtual Reference Vector

In order to obtain bio-impedance information at different frequency simultaneously, the bio-impedance measurement method in the condition of mixing frequency excitation is studied in this paper. The influence of energy leakage and fence effect of DFT to sine signal detection is analyzed, according to which the bio-impedance measurement technology based on DFT with virtual reference vector is presented. Finally, compensation of virtual reference vector is certificated by emulations and experiments. From the experimental results, the dynamic reaction of respiratory and cardiac activity in different frequency can be manifested according to the human impedance measurement.

Design of Programmable Threshold Value Discrimination for Compton Scattering System Based on FPGA

According to the characteristics of multi-angle array Compton scattering data, a programmable threshold value discrimination system was designed. The system can read Compton scattering solution spectrum information, and sends it to FPGA module, which drive 8 DAC chips. FPGA programmed by Verilog HDL Language receives control commands from PC by serial port, then it will rapidly drive DACs to give accurate threshold values. The test shows that the system with extended design of DAC based on FPGA can give high precise and highly stabile threshold value discrimination voltage, and the values with well programmable control performance, it was suitable for the multi-angle array Compton scattering system.

Modeling of the conductive ring electrical impedance tomography sensor

Conductive ring electrical impedance tomography sensor presents a new way to take non-invasive measurements of resistance for electrical tomography. This paper introduces its advantageous features and develops a model for the sensor. Verified by experiment, this model enables the raw measurement data to be converted to material impedance data, providing accurate input data for reconstruction algorithms.

Design of ERT/ECT dual-modality process tomography system

With the development of multiphase flow, real-time tomography system sensitive to various electrical parameters is required, i.e. multi-modal real-time tomography system. From the perspective of the electromagnetic field theory, electrical resistance tomography (ERT) and electrical capacitance tomography (ECT) are classified to a same mathematical model. Composite sensor array and hardware circuit featured with topological structure for the ERT/ECT dual-modality system are designed. The system can run in single modality or dual modality, fusion of ERT and ECT is realized primarily. Some key problems in hardware are discussed in this paper, including the design of C/V and R/V converted circuits, as well as how to design analog switches to reduce the coupling between dual-modal sensors. Reconstruction images based on Landweber iterative algorithm are in agreement with experiments and the system is verified stable and flexible.

Primary Study on Dielectric Property Detection for Cerebral Haematoma

Its found that the distinction of permittivity of different tissues is more obvious, according to analyzing the changing regularity of the conductivity and permittivity of the head tissue at different frequency. A capacitance measuring method based on dielectric property is presented, which aims at detecting the haematoma as well as its development expediently. According to the head structure, a multi-layer head model is built up with ANSYS analysis software. The different states of haematoma such as the position, size and the extent of approaching the measuring electrode are analyzed in two-dimension model. The feasibility of the measurement is proved.

Integrated Computer-aided Control and Optimization of Béchamel Production Processes

The quality of a product is traditionally assayed after routine operations before being packaged. If the specifications are not qualified, it means lots of material will be wasted and even can not be reused any more. There are two limitations of the conventional process control: one is that the corrective action is often taken after assay, the other is that most of the time correct assignable cause of variation is not known. How to avoid material wasting, financial loss and throughput debasing is a disturbing problem. To meet this challenge, a strategy of integrated computer-aided process control is proposed. This paper presents a methodology for the computer-based control and optimization of a bechamel production line. The system provides not only monitoring and controlling in real time but also the optimization of the whole process. Information in process in turn is used to identify assignable cause of variations in product quality, presence of extraneous influences and deterioration of certain equipment. In addition, such information is useful for the failure diagnostics and the recommendation of repair procedure. The optimized process design can realize reasonable structure at low cost; at the same time such design scheme can also contribute to pollution reduction as well as energy conservation.