This article deals with two important issues in digital filter implementation： roundoff noise and limit cycles. A novel class of robust state-space realizations, called normal realizations, is derived and characteriz...This article deals with two important issues in digital filter implementation： roundoff noise and limit cycles. A novel class of robust state-space realizations, called normal realizations, is derived and characterized. It is seen that these realizations are free of limit cycles. Another interesting property of the normal realizations is that they yield a minimal error propagation gain. The optimal realization problem, defined as to find those normal realizations that minimize roundoff noise gain, is formulated and solved analytically. A design example is presented to demonstrate the behavior of the optimal normal realizations and to compare them with several well-known digital filter realizations in terms of minimizing the roundoff noise and the error propagation.展开更多
The wavelength shift in fiber Bragg grating does not depend directly on the total light levels, losses in the connecting fibers and couplers, or source power. However, if the tunable Fabry-Perot filter is place on the...The wavelength shift in fiber Bragg grating does not depend directly on the total light levels, losses in the connecting fibers and couplers, or source power. However, if the tunable Fabry-Perot filter is place on the end of incident fiber, the detected time delay of modulation light is occurred due to the unmatch between the scanning time and light transmission time in the transmission fiber. Consequently, the detected peak wavelength shifts with the length of transmission fiber. Thus, the peak wavelength shift effect of Bragg reflective light transmitted in fiber with different fiber length can be obvious in the demodulator with a prepositive tunable Fabry-Perot filter. The experiment indicates the shift rates of 0.109 - 0.126 nm/km increase approximately linearly with the original peak wavelength of 1532.917 - 1560.300 nm at the fiber length of 0 - 6 km. To certify the consistency of measurement data, the criterion correction is introduced. By using the differential method of two fiber Bragg gratings with an optical path, the differential worth is compensated from the disturbance modulated by the time delay of fiber length.展开更多
The optical wavelet filter is designed. It can filter and choose frequency swiftly. It can realize demodulation of distributed fiber Bragg grating（FBG） measurement system. Its scanning resolution and scanning period...The optical wavelet filter is designed. It can filter and choose frequency swiftly. It can realize demodulation of distributed fiber Bragg grating（FBG） measurement system. Its scanning resolution and scanning period depend on wavelet function. Wavelet function is controlled by computer. Compared to conventional scan filter, optical wavelet filtering has some advantages such as simple structure, high scan frequency, high resolution and good linearity. At last, the error of optical wavelet filter scanning procedure is analyzed. Scanning step length refers to the shifting of optical wavelet window＇s central frequency. It affects system precision directly. If scanning step length is different, the measured signal is different. The methods of reducing step length guarantee scanning periodic time are presented.展开更多
The effectiveness of deep-bed filtration with respect to suspension formed during the preceding processes is evaluated by the test of filterability. The properties and concentration of the suspension being filtered ar...The effectiveness of deep-bed filtration with respect to suspension formed during the preceding processes is evaluated by the test of filterability. The properties and concentration of the suspension being filtered are affected by the efficiency of the preceding aggregation and separation processes. The basic principles of the test of filterability are based on the mechanistic model of filtration. The equations in the mathematical model of the mechanistic conception of filtration are derived from the theory of filtration. The arrangement of the pilot filtration plant for the determination of filterability of flocculent suspension is presented in this paper. The test of filterability is carried out with a thin-layer filter element. The design of a filter element arrangement and its installation are also disclosed in this paper. The inter-dependence of the coefficient of filtration efficiency on the specific volume of intercepted suspensions, filter media grain sizes and different filtration velocities are graphically presented. In addition, the effect of the filter bed clogging resulting from the properties of different suspensions on the head loss generated, the length of filtration cycle and quality of filtrate produced are also shown in this paper.展开更多
原始观测时间序列进行数字滤波后,其自由度将大大降低。对各种数字滤波器都可以通过 Monte Carlo方法模拟获得对应置信水平的相关系数临界值,从而得到时间序列滤波后的自由度。如果滤波后的频段宽度与Nyquist频率之比为Z,那么对于理想...原始观测时间序列进行数字滤波后,其自由度将大大降低。对各种数字滤波器都可以通过 Monte Carlo方法模拟获得对应置信水平的相关系数临界值,从而得到时间序列滤波后的自由度。如果滤波后的频段宽度与Nyquist频率之比为Z,那么对于理想的单边和双边滤波器,时间序列滤波后的自由度为原始值的Z/2和Z倍,非理想滤波器一般不符合此规律。展开更多
基金Supported by the Funds for Creative Research Groups of China 60521003）, the State Key Program of National Natural Science of ina （60534010）, National Natural Science Foundation of China （60674021）, the Funds of Ph.D. Program of Ministry of Eduction, China （20060145019）, and the 111 Project （B08015）
文摘过滤有限的词长度(FWL ) 为线性分离时间的系统影响的问题的 nonfragile H 在这份报纸被调查。要设计的过滤器被假定与添加剂获得变化，它在过滤器实现上反映 FWL 效果。结构化的顶点隔板的一个观点被建议处理这个问题并且利用了以一套线性矩阵不平等(LMI ) 为 nonfragile H 过滤器设计开发足够的条件。设计使扩充系统变为 asymptotically 稳定并且保证 H 变细水平不到规定水平。一个数字例子被给说明建议方法的效果。
基金the National Nature Science Foundation of China (60774021)
文摘This article deals with two important issues in digital filter implementation： roundoff noise and limit cycles. A novel class of robust state-space realizations, called normal realizations, is derived and characterized. It is seen that these realizations are free of limit cycles. Another interesting property of the normal realizations is that they yield a minimal error propagation gain. The optimal realization problem, defined as to find those normal realizations that minimize roundoff noise gain, is formulated and solved analytically. A design example is presented to demonstrate the behavior of the optimal normal realizations and to compare them with several well-known digital filter realizations in terms of minimizing the roundoff noise and the error propagation.
文摘The wavelength shift in fiber Bragg grating does not depend directly on the total light levels, losses in the connecting fibers and couplers, or source power. However, if the tunable Fabry-Perot filter is place on the end of incident fiber, the detected time delay of modulation light is occurred due to the unmatch between the scanning time and light transmission time in the transmission fiber. Consequently, the detected peak wavelength shifts with the length of transmission fiber. Thus, the peak wavelength shift effect of Bragg reflective light transmitted in fiber with different fiber length can be obvious in the demodulator with a prepositive tunable Fabry-Perot filter. The experiment indicates the shift rates of 0.109 - 0.126 nm/km increase approximately linearly with the original peak wavelength of 1532.917 - 1560.300 nm at the fiber length of 0 - 6 km. To certify the consistency of measurement data, the criterion correction is introduced. By using the differential method of two fiber Bragg gratings with an optical path, the differential worth is compensated from the disturbance modulated by the time delay of fiber length.
基金This project is supported by National Natural Science Foundation of China(No.60377002).
文摘The optical wavelet filter is designed. It can filter and choose frequency swiftly. It can realize demodulation of distributed fiber Bragg grating（FBG） measurement system. Its scanning resolution and scanning period depend on wavelet function. Wavelet function is controlled by computer. Compared to conventional scan filter, optical wavelet filtering has some advantages such as simple structure, high scan frequency, high resolution and good linearity. At last, the error of optical wavelet filter scanning procedure is analyzed. Scanning step length refers to the shifting of optical wavelet window＇s central frequency. It affects system precision directly. If scanning step length is different, the measured signal is different. The methods of reducing step length guarantee scanning periodic time are presented.
文摘The effectiveness of deep-bed filtration with respect to suspension formed during the preceding processes is evaluated by the test of filterability. The properties and concentration of the suspension being filtered are affected by the efficiency of the preceding aggregation and separation processes. The basic principles of the test of filterability are based on the mechanistic model of filtration. The equations in the mathematical model of the mechanistic conception of filtration are derived from the theory of filtration. The arrangement of the pilot filtration plant for the determination of filterability of flocculent suspension is presented in this paper. The test of filterability is carried out with a thin-layer filter element. The design of a filter element arrangement and its installation are also disclosed in this paper. The inter-dependence of the coefficient of filtration efficiency on the specific volume of intercepted suspensions, filter media grain sizes and different filtration velocities are graphically presented. In addition, the effect of the filter bed clogging resulting from the properties of different suspensions on the head loss generated, the length of filtration cycle and quality of filtrate produced are also shown in this paper.
文摘为了研究基于相干光纤束(Coherent Fiber Bundle,CFB)的无扫描无透镜柔性光学内窥相位成像技术中纤芯误差对成像的影响,针对CFB的传输模式和纤芯长度误差,利用波动光学理论建立了基于CFB的无扫描无透镜柔性光学内窥2D相位成像的理论模型,数学仿真了不同传输模式或纤芯长度误差对成像的影响。结果表明:单模传输和多模传输下的成像分辨率不同,多模传输下具有超衍射极限分辨率的现象。纤芯长度误差对成像影响严重,纤芯长度误差较大时无法成像,纤芯长度误差较小时,成像信噪比降低。对小纤芯长度误差影响的低信噪比模糊图像,可采用维纳滤波,几次迭代后,图像的信噪比均能提升5 d B以上,图像的归一化均方根误差均小于0.5,有效改善了图像质量。因此,在基于CFB的无扫描无透镜柔性光学内窥相位成像系统中,为了实现成像,需要采用单模CFB或在多模CFB中抑制多模实现单模运转。
文摘原始观测时间序列进行数字滤波后,其自由度将大大降低。对各种数字滤波器都可以通过 Monte Carlo方法模拟获得对应置信水平的相关系数临界值,从而得到时间序列滤波后的自由度。如果滤波后的频段宽度与Nyquist频率之比为Z,那么对于理想的单边和双边滤波器,时间序列滤波后的自由度为原始值的Z/2和Z倍,非理想滤波器一般不符合此规律。
