A global optimum location algorithm called Variable Step-Size Generalized Simulated Annealing(VSGSA) was applied to treating the data obtained by using an array of ion-electrodes in solutions containing mixtures of Na...A global optimum location algorithm called Variable Step-Size Generalized Simulated Annealing(VSGSA) was applied to treating the data obtained by using an array of ion-electrodes in solutions containing mixtures of Na+, K+, Ca2+. Unlike traditional optimization algorithms such as simplex procedure, VSGSA can be used to determine the model parameters without any priori information about the analytical system under investigation and overcome the disadvantage of simplex method which might converge to local extrema depending on the starting positions. The algorithm was applied to po-tentiometric determination of ions in mixture solutions.展开更多
Two small scale acoustic phased arrays with 4 elements have been designed and assembled in the laboratory. Experiments have been carried out with them. It is found that both directivity and radiation lobe width of the...Two small scale acoustic phased arrays with 4 elements have been designed and assembled in the laboratory. Experiments have been carried out with them. It is found that both directivity and radiation lobe width of the phased array can be regulated by changing the time delay between the input signals on neighboring elements. Results measured are in good agreement with those calculated. By using the phased array as an acoustic transmitter and hydrophone as a receiver, small scale acoustic well-logging simulations have been carried out both on an aluminum modei well and on a concrete one. Experimental results show that, by increasing the time delay of the input signals on neighboring elements, the steered radiation angle of the phased array becomes larger and larger, and generation conditions of the refracted compressional wave and the refracted shear wave are reached successively, and the refracted compressional wave, the refracted shear wave and the Stoneley wave are strengthened, respec-tively. Therefore, by choosing element spacing of a phased array and acoustic wave frequency appropriately, the main radiation lobe of the phased array can be widened to cover the first critical angle of all kinds of formations, which makes it possible to apply phased array acoustic well-logging in any formation continuously without regulating directivity of the phased array.展开更多
The Principles of coherent interference suppression are presented by a three-sensor array. The formulae of extracting expected signals from strong interference are derived. The selection of sensor space is discussed a...The Principles of coherent interference suppression are presented by a three-sensor array. The formulae of extracting expected signals from strong interference are derived. The selection of sensor space is discussed and then relationships between the space and frequency point, at which the signals can be extracted, are given. When expected signals are band- limit, the conditions of the selected sensor space, which should be satisfied, are given. Lastly, Performance of interference suppression is analyzed when the amplitude of interference power spectra of signals Received by three sensors fluctuates, and the expressions of relative error of the extracted signals and processing gain are derived. The theoretical and simulation results show that signals can be extracted from strong background interference without any information about signals and interference expect for the arriving direction of signals, that the space between sensors should be smaller than half wavelength of upper limit freqency when the expected signals are band-limit, and that performance of extracting signals will decline with the increase of fluctuation of interference spectrum amplitude.展开更多
基金Supported by the National Natural Science Foundation of China Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Academia Sinica
文摘A global optimum location algorithm called Variable Step-Size Generalized Simulated Annealing(VSGSA) was applied to treating the data obtained by using an array of ion-electrodes in solutions containing mixtures of Na+, K+, Ca2+. Unlike traditional optimization algorithms such as simplex procedure, VSGSA can be used to determine the model parameters without any priori information about the analytical system under investigation and overcome the disadvantage of simplex method which might converge to local extrema depending on the starting positions. The algorithm was applied to po-tentiometric determination of ions in mixture solutions.
文摘Two small scale acoustic phased arrays with 4 elements have been designed and assembled in the laboratory. Experiments have been carried out with them. It is found that both directivity and radiation lobe width of the phased array can be regulated by changing the time delay between the input signals on neighboring elements. Results measured are in good agreement with those calculated. By using the phased array as an acoustic transmitter and hydrophone as a receiver, small scale acoustic well-logging simulations have been carried out both on an aluminum modei well and on a concrete one. Experimental results show that, by increasing the time delay of the input signals on neighboring elements, the steered radiation angle of the phased array becomes larger and larger, and generation conditions of the refracted compressional wave and the refracted shear wave are reached successively, and the refracted compressional wave, the refracted shear wave and the Stoneley wave are strengthened, respec-tively. Therefore, by choosing element spacing of a phased array and acoustic wave frequency appropriately, the main radiation lobe of the phased array can be widened to cover the first critical angle of all kinds of formations, which makes it possible to apply phased array acoustic well-logging in any formation continuously without regulating directivity of the phased array.
文摘The Principles of coherent interference suppression are presented by a three-sensor array. The formulae of extracting expected signals from strong interference are derived. The selection of sensor space is discussed and then relationships between the space and frequency point, at which the signals can be extracted, are given. When expected signals are band- limit, the conditions of the selected sensor space, which should be satisfied, are given. Lastly, Performance of interference suppression is analyzed when the amplitude of interference power spectra of signals Received by three sensors fluctuates, and the expressions of relative error of the extracted signals and processing gain are derived. The theoretical and simulation results show that signals can be extracted from strong background interference without any information about signals and interference expect for the arriving direction of signals, that the space between sensors should be smaller than half wavelength of upper limit freqency when the expected signals are band-limit, and that performance of extracting signals will decline with the increase of fluctuation of interference spectrum amplitude.
