研究了智能变电站普遍采用的线性插值法,并针对幅值衰减问题提出了改进方法。首先采用离散传递函数的方法,推导了线性插值的幅值增益公式。进而分析了线性插值的幅频特性,并评估了幅值衰减对保护、测控等环节的影响。在现有的4 k Hz采...研究了智能变电站普遍采用的线性插值法,并针对幅值衰减问题提出了改进方法。首先采用离散传递函数的方法,推导了线性插值的幅值增益公式。进而分析了线性插值的幅频特性,并评估了幅值衰减对保护、测控等环节的影响。在现有的4 k Hz采样率下,线性插值不能完全满足采样环节对谐波幅值精度的要求。在此基础上,利用幅值增益相对于插值位置的对称性,提出了一种改进的插值方法。经理论证明,该方法对各频率信号的幅值增益恒为1。然后,给出了该方法的软件实现过程,特别是初值的选择,并分析了算法的稳定性。最后,结合具体的波形,通过FFT分析验证了该方法的插值效果。分析结果表明,所提的改进方法可以解决线性插值的幅值衰减问题。展开更多
Based on the constant coefficients of Ginzburg-Landau equation that considers the influence of the doped fiber retarded time on the evolution of self-similar pulse,the parabolic asymptotic self-similar solutions were ...Based on the constant coefficients of Ginzburg-Landau equation that considers the influence of the doped fiber retarded time on the evolution of self-similar pulse,the parabolic asymptotic self-similar solutions were obtained by the symmetry reduc-tion algorithm. The parabolic asymptotic amplitude function,phase function,strict linear chirp function and the effective temporal pulse width of self-similar pulse are given in this paper. And these theoretical results are consistent with the numerical simulations.展开更多
Using Harrison's model and anisotropic parabolic approximation,the band structure of In1- x- y Gay Alx As compressively strained quantum wells is calculated.To design lasers with1.55μm wavelength,it is necessary...Using Harrison's model and anisotropic parabolic approximation,the band structure of In1- x- y Gay Alx As compressively strained quantum wells is calculated.To design lasers with1.55μm wavelength,it is necessary to an- alyze the well width,differential gain,transparency carrier density and the characteristic gain for an arbitrary com- position.Some useful empirical formulas are also presented.展开更多
A novel wide-range CMOS variable gain amplifier （VGA） topology is presented. The proposed VGA is composed of a variable transconductor and a novel variable output resistor and can offer a high gain variation range o...A novel wide-range CMOS variable gain amplifier （VGA） topology is presented. The proposed VGA is composed of a variable transconductor and a novel variable output resistor and can offer a high gain variation range of 80dB while using a single variable-gain stage. Temperature-compensation and decibel-linear gain characteristic are achieved by using a control circuit that provides a gain error lower than ±1.5dB over the full temperature and gain ranges. Realized in 0.25μm CMOS technology, a prototype of the proposed VGA provides a total gain range of 64.5dB with 55.6dB-linear range,a P-1dB varying from - 17.5 to 11.5dBm,and a 3dB-bandwith varying from 65 to 860MHz while dissipating 16.5mW from a 2.5V supply voltage.展开更多
The aperture phase taper due to quadratic phase errors in the principal planes of a rectangular horn imposes signifi-cant constraints on the on-axis far-field gain of the horn. The precise calculation of gain reductio...The aperture phase taper due to quadratic phase errors in the principal planes of a rectangular horn imposes signifi-cant constraints on the on-axis far-field gain of the horn. The precise calculation of gain reduction involves Fresnel integrals;therefore, exact results are obtained only from numerical methods. However, in horns’ analysis and design, simple closed-form expressions are often required for the description of horn-gain. This paper provides a set of simple polynomial approximations that adequately describe the gain reduction factors of pyramidal and sectoral horns. The proposed formulas are derived using least-squares polynomial regression analysis and they are valid for a broad range of quadratic phase error values. Numerical results verify the accuracy of the derived expressions. Application examples and comparisons with methods in the literature demonstrate the efficacy of the approach.展开更多
The study was conducted to evaluate the fattening performance of Arsi, Borana, Harar and Holstein Friesian crossbred bulls finished under a similar feeding condition at the beef farm in Haramaya University. The averag...The study was conducted to evaluate the fattening performance of Arsi, Borana, Harar and Holstein Friesian crossbred bulls finished under a similar feeding condition at the beef farm in Haramaya University. The average daily weight gain of the four breeds ranges from 0.49 to 0.71 kg. Feed conversion efficiency also ranges from 0.11 - 0.15. Simple linear regression models were used to explore the relationship between live body weight change and change in body condition score as well as seven linear body measurements for all age groups. An average change for a unite of body condition score was equivalent to 20.3, 20.61, 22.42 and 27.78 kg for Borana, Arsi, Harar and Holstein Friesian crossbred bulls respectively. Body condition score was significantly influenced by breeds. There was a significant breed by age interaction effect on the initial body condition score of the four breeds. There was a significant and positive strong association between change in body weight and body condition score. There was a significant and strong correlation between change in body weight and change in Total topline, neck length, heart girth, flank circumference and rump length having correlation coefficients ranges from 0.57 to 0.97. A higher net profit of 7380.47 ETB per head was recorded by Borana bulls followed by Harar bulls, Arsi and Holstein Friesian crossbred with net profit of 5406.86, 5193.29 and 3384.98 ETB per head respectively. Borana bulls are more superior in weight gain and net profit. Bodyweight change could be predicted based on body condition score change during the fattening period.展开更多
本文主要介绍了一种基于矢量网络分析仪的低噪声放大器测试系统,借助矢量网络分析仪和直流电源即可准确高效地测试低噪声放大器的线性增益、输入/输出驻波比、工作电流、1 d B压缩功率、噪声系数等参数,并且编写了一套自动测试程序进行...本文主要介绍了一种基于矢量网络分析仪的低噪声放大器测试系统,借助矢量网络分析仪和直流电源即可准确高效地测试低噪声放大器的线性增益、输入/输出驻波比、工作电流、1 d B压缩功率、噪声系数等参数,并且编写了一套自动测试程序进行数据记录和处理。该系统相比于传统的测试系统,在精度、效率与集成度上均有较大提升。展开更多
文摘研究了智能变电站普遍采用的线性插值法,并针对幅值衰减问题提出了改进方法。首先采用离散传递函数的方法,推导了线性插值的幅值增益公式。进而分析了线性插值的幅频特性,并评估了幅值衰减对保护、测控等环节的影响。在现有的4 k Hz采样率下,线性插值不能完全满足采样环节对谐波幅值精度的要求。在此基础上,利用幅值增益相对于插值位置的对称性,提出了一种改进的插值方法。经理论证明,该方法对各频率信号的幅值增益恒为1。然后,给出了该方法的软件实现过程,特别是初值的选择,并分析了算法的稳定性。最后,结合具体的波形,通过FFT分析验证了该方法的插值效果。分析结果表明,所提的改进方法可以解决线性插值的幅值衰减问题。
基金the Natural Science Foundation of Guangdong Province of China (Grant No. 04010397)
文摘Based on the constant coefficients of Ginzburg-Landau equation that considers the influence of the doped fiber retarded time on the evolution of self-similar pulse,the parabolic asymptotic self-similar solutions were obtained by the symmetry reduc-tion algorithm. The parabolic asymptotic amplitude function,phase function,strict linear chirp function and the effective temporal pulse width of self-similar pulse are given in this paper. And these theoretical results are consistent with the numerical simulations.
文摘Using Harrison's model and anisotropic parabolic approximation,the band structure of In1- x- y Gay Alx As compressively strained quantum wells is calculated.To design lasers with1.55μm wavelength,it is necessary to an- alyze the well width,differential gain,transparency carrier density and the characteristic gain for an arbitrary com- position.Some useful empirical formulas are also presented.
文摘A novel wide-range CMOS variable gain amplifier （VGA） topology is presented. The proposed VGA is composed of a variable transconductor and a novel variable output resistor and can offer a high gain variation range of 80dB while using a single variable-gain stage. Temperature-compensation and decibel-linear gain characteristic are achieved by using a control circuit that provides a gain error lower than ±1.5dB over the full temperature and gain ranges. Realized in 0.25μm CMOS technology, a prototype of the proposed VGA provides a total gain range of 64.5dB with 55.6dB-linear range,a P-1dB varying from - 17.5 to 11.5dBm,and a 3dB-bandwith varying from 65 to 860MHz while dissipating 16.5mW from a 2.5V supply voltage.
文摘The aperture phase taper due to quadratic phase errors in the principal planes of a rectangular horn imposes signifi-cant constraints on the on-axis far-field gain of the horn. The precise calculation of gain reduction involves Fresnel integrals;therefore, exact results are obtained only from numerical methods. However, in horns’ analysis and design, simple closed-form expressions are often required for the description of horn-gain. This paper provides a set of simple polynomial approximations that adequately describe the gain reduction factors of pyramidal and sectoral horns. The proposed formulas are derived using least-squares polynomial regression analysis and they are valid for a broad range of quadratic phase error values. Numerical results verify the accuracy of the derived expressions. Application examples and comparisons with methods in the literature demonstrate the efficacy of the approach.
文摘The study was conducted to evaluate the fattening performance of Arsi, Borana, Harar and Holstein Friesian crossbred bulls finished under a similar feeding condition at the beef farm in Haramaya University. The average daily weight gain of the four breeds ranges from 0.49 to 0.71 kg. Feed conversion efficiency also ranges from 0.11 - 0.15. Simple linear regression models were used to explore the relationship between live body weight change and change in body condition score as well as seven linear body measurements for all age groups. An average change for a unite of body condition score was equivalent to 20.3, 20.61, 22.42 and 27.78 kg for Borana, Arsi, Harar and Holstein Friesian crossbred bulls respectively. Body condition score was significantly influenced by breeds. There was a significant breed by age interaction effect on the initial body condition score of the four breeds. There was a significant and positive strong association between change in body weight and body condition score. There was a significant and strong correlation between change in body weight and change in Total topline, neck length, heart girth, flank circumference and rump length having correlation coefficients ranges from 0.57 to 0.97. A higher net profit of 7380.47 ETB per head was recorded by Borana bulls followed by Harar bulls, Arsi and Holstein Friesian crossbred with net profit of 5406.86, 5193.29 and 3384.98 ETB per head respectively. Borana bulls are more superior in weight gain and net profit. Bodyweight change could be predicted based on body condition score change during the fattening period.
文摘本文主要介绍了一种基于矢量网络分析仪的低噪声放大器测试系统,借助矢量网络分析仪和直流电源即可准确高效地测试低噪声放大器的线性增益、输入/输出驻波比、工作电流、1 d B压缩功率、噪声系数等参数,并且编写了一套自动测试程序进行数据记录和处理。该系统相比于传统的测试系统,在精度、效率与集成度上均有较大提升。
