Propagation characterization is one of the main building blocks for millimetre wave （MMW） communication. The Gaussian beam has attractive features to become a prospective wave form for millimetre radio communication...Propagation characterization is one of the main building blocks for millimetre wave （MMW） communication. The Gaussian beam has attractive features to become a prospective wave form for millimetre radio communication, especially for the utility inside tunnels. A ray tracing method embedded with spectral features of Gaussian beam is employed to analyze mil- limetre wave propagation in a circle tunnel in this paper. In consideration of geometrical figure of the tunnel, the superposition behaviour of direct and reflective beams is analyzed via simplified approximation of Gaussian beam spectral feature. Then the propagation models are established to derive amplitude, phase, and delay spread of received wave. A typical straight tunnel model is used to simulate the propagation behaviour, where strong multi-path effect with deeply fading of signal intensity and dramatically enhancing of delay spread emerges. For investigation of the spectral feature of the multi-path effect, a reflection loss of 14 dB is taken into consideration at a designated point. To analyze the influences of frequency and transmission distance, the propagation characteristics at three different frequencies of 45 GHz, 65 GHz and 85 GHz are compared with the beam travelling down the tunnel. In addition, three different reflection losses of 14 dB, 20 dB, and 26 dB at the frequency of 65 GHz are also investigated to research the influence of the reflecting coefficient.展开更多
In this paper, without recourse to the nonlinear dynamical equations of the waves, the nonlinear random waves are retrieved from the non-Gaussian characteristic of the sea surface elevation distribution. The question ...In this paper, without recourse to the nonlinear dynamical equations of the waves, the nonlinear random waves are retrieved from the non-Gaussian characteristic of the sea surface elevation distribution. The question of coincidence of the nonlinear wave profile, spectrum and its distributions of maximum (or minimum) values of the sea surface elevation with results derived from some existing nonlinear theories is expounded under the narrow-band spectrum condition. Taking the shoaling sea wave as an example, the nonlinear random wave process and its spectrum in shallow water are retrieved from both the non-Gaussian characteristics of the sea surface elevation distribution in shallow water and the normal sea waves in deep water and compared with the values actually measured. Results show that they can coincide with the actually measured values quite well, thus, this can confirm that the method proposed in this paper is feasible.展开更多
The probability distributions of wave characteristics from three groups of sampled ocean data with different significant wave heights have been analyzed using two transformation functions estimated by non-parametric a...The probability distributions of wave characteristics from three groups of sampled ocean data with different significant wave heights have been analyzed using two transformation functions estimated by non-parametric and parametric methods. The marginal wave characteristic distribution and the joint density of wave properties have been calculated using the two transformations, with the results and accuracy of both transformations presented here. The two transformations deviate slightly between each other for the calculation of the crest and trough height marginal wave distributions, as well as the joint densities of wave amplitude with other wave properties. The transformation methods for the calculation of the wave crest and trough height distributions are shown to provide good agreement with real ocean data. Our work will help in the determination of the most appropriate transformation procedure for the prediction of extreme values.展开更多
叶绿素含量是植物生长状况的重要指标。传统的测量叶绿素的方法费时费力,会对植物造成损伤。近年来,数字图像处理技术在估测植物叶绿素含量方向上取得了较好的进展,但针对银杏等经济林木的研究依旧偏少。以不同水氮互作条件下的2年生银...叶绿素含量是植物生长状况的重要指标。传统的测量叶绿素的方法费时费力,会对植物造成损伤。近年来,数字图像处理技术在估测植物叶绿素含量方向上取得了较好的进展,但针对银杏等经济林木的研究依旧偏少。以不同水氮互作条件下的2年生银杏幼苗为研究对象,使用数字扫描仪采集银杏幼苗叶片图像,利用数字图像技术构建颜色特征参数,结合相关性分析初筛出对叶绿素显著相关的颜色特征参数,并进一步基于高斯过程回归(gaussian process regression, GPR)和偏最小二乘回归(partial least squares regression, PLSR)优选建模中最为重要的颜色特征参数,建立基于银杏叶片颜色特征参数的叶绿素含量估测模型。结果表明,叶绿素含量随着施氮水平和水分处理水平的上升总体上呈现逐渐提高而后缓慢下降的趋势。基于单一颜色参数建立的单变量回归模型(R^(2)=0.01~0.72)预测精度总体上低于使用高斯过程回归(R^(2)=0.79~0.81)和偏最小二乘法(R^(2)=0.75~0.77)的模型。其中,GPR-BAT模型和PLSR-VIP模型都筛选出了对叶绿素敏感的R、G颜色特征参数;GPR模型的表现总体上优于PLSR模型,特别是在使用GPR-BAT优选颜色参数建模时表现最佳(R^(2)=0.81)。基于GPR-BAT优选颜色参数构建的GPR模型效果最佳,可准确估测银杏叶片叶绿素含量,为银杏生产的精确管理和监测银杏生长状况提供技术支撑。展开更多
Currently, the approximation methods of the Gaussian filter by some other spline filters have been developed. However, thesc methods are only suitable for the study of one-dimensional filtering, when these methods are...Currently, the approximation methods of the Gaussian filter by some other spline filters have been developed. However, thesc methods are only suitable for the study of one-dimensional filtering, when these methods are used for three-dimensional filtering, it is found that a rounding error and quantization error would be passed to the next in every part. In this paper, a new and high-precision implementation approach for Gaussian filter is described, which is suitable for three-dimensional reference filtering. Based on the theory of generalized B-spline function and the variational principle, the transmission characteristics of a digital filter can be changed through the sensitivity of the parameters （t1, t2）, and which can also reduce the rounding error and quantization error by the filter in a parallel form instead of the cascade form, Finally, the approximation filter of Gaussian filter is obtained. In order to verify the feasibility of the new algorithm, the reference extraction of the conventional methods are also used and compared. The experiments are conducted on the measured optical surface, and the results show that the total calculation by the new algorithm only requires 0.07 s for 480×480 data points; the amplitude deviation between the reference of the parallel form filter and the Gaussian filter is smaller; the new method is closer to the characteristic of the Gaussian filter through the analysis of three-dimensional roughness parameters, comparing with the cascade generalized B-spline approximating Gaussian. So the new algorithm is also efficient and accurate for the implementation of Gaussian filter in the application of surface roughness measurement.展开更多
An inequality describing the difference between Gamma and Gaussian distributions is derived. The asymptotic bound is much better than by existing uniform bound from Berry-Esseen inequality.
在运输过程中,包装件经常受到非高斯随机振动的作用,在进行包装系统优化时,经常需要重复确定包装件加速度响应的统计特征和振动可靠性,该研究提出一种高效准确确定非高斯随机振动条件下非线性包装件加速度响应统计特征的分析方法。采用...在运输过程中,包装件经常受到非高斯随机振动的作用,在进行包装系统优化时,经常需要重复确定包装件加速度响应的统计特征和振动可靠性,该研究提出一种高效准确确定非高斯随机振动条件下非线性包装件加速度响应统计特征的分析方法。采用非高斯Karhunen-Loeve展开将非高斯随机振动表示为非高斯随机变量的线性组合,用一阶泰勒展开估计包装件加速度响应,确定加速度响应的统计矩参数,根据包装件加速度响应的前四阶矩参数,应用鞍点估计法确定包装件加速度响应的概率密度函数(probability density function, PDF)和累积分布函数(cumulative distribution function, CDF)。由于采用随机变量的线性组合模拟非高斯随机振动激励,避免了随机变量非线性变换,采用一阶泰勒展开估计包装件加速度响应具有良好的准确性,鞍点估计法分析包装件加速度响应的PDF和CDF,避免了大量蒙特卡洛或拟蒙特卡洛分析,提高了分析效率。展开更多
基金supported by the Shanghai Leading Academic Discipline Project (Grant No.S30108)the Science and Technology Commission of Shanghai Municipality (Grant No.08DZ2231100)
文摘Propagation characterization is one of the main building blocks for millimetre wave （MMW） communication. The Gaussian beam has attractive features to become a prospective wave form for millimetre radio communication, especially for the utility inside tunnels. A ray tracing method embedded with spectral features of Gaussian beam is employed to analyze mil- limetre wave propagation in a circle tunnel in this paper. In consideration of geometrical figure of the tunnel, the superposition behaviour of direct and reflective beams is analyzed via simplified approximation of Gaussian beam spectral feature. Then the propagation models are established to derive amplitude, phase, and delay spread of received wave. A typical straight tunnel model is used to simulate the propagation behaviour, where strong multi-path effect with deeply fading of signal intensity and dramatically enhancing of delay spread emerges. For investigation of the spectral feature of the multi-path effect, a reflection loss of 14 dB is taken into consideration at a designated point. To analyze the influences of frequency and transmission distance, the propagation characteristics at three different frequencies of 45 GHz, 65 GHz and 85 GHz are compared with the beam travelling down the tunnel. In addition, three different reflection losses of 14 dB, 20 dB, and 26 dB at the frequency of 65 GHz are also investigated to research the influence of the reflecting coefficient.
基金This work is funded by National Natural Science Foundation of China
文摘In this paper, without recourse to the nonlinear dynamical equations of the waves, the nonlinear random waves are retrieved from the non-Gaussian characteristic of the sea surface elevation distribution. The question of coincidence of the nonlinear wave profile, spectrum and its distributions of maximum (or minimum) values of the sea surface elevation with results derived from some existing nonlinear theories is expounded under the narrow-band spectrum condition. Taking the shoaling sea wave as an example, the nonlinear random wave process and its spectrum in shallow water are retrieved from both the non-Gaussian characteristics of the sea surface elevation distribution in shallow water and the normal sea waves in deep water and compared with the values actually measured. Results show that they can coincide with the actually measured values quite well, thus, this can confirm that the method proposed in this paper is feasible.
基金Supported by the Marine Engineering Equipment Scientific Research Project of Ministry of Industry and Information Technology of PRCthe National Science and Technology Major Project of China(Grant No.2016ZX05057020)National Natural Science Foundation of China(Grant No.51809067)
文摘The probability distributions of wave characteristics from three groups of sampled ocean data with different significant wave heights have been analyzed using two transformation functions estimated by non-parametric and parametric methods. The marginal wave characteristic distribution and the joint density of wave properties have been calculated using the two transformations, with the results and accuracy of both transformations presented here. The two transformations deviate slightly between each other for the calculation of the crest and trough height marginal wave distributions, as well as the joint densities of wave amplitude with other wave properties. The transformation methods for the calculation of the wave crest and trough height distributions are shown to provide good agreement with real ocean data. Our work will help in the determination of the most appropriate transformation procedure for the prediction of extreme values.
文摘叶绿素含量是植物生长状况的重要指标。传统的测量叶绿素的方法费时费力,会对植物造成损伤。近年来,数字图像处理技术在估测植物叶绿素含量方向上取得了较好的进展,但针对银杏等经济林木的研究依旧偏少。以不同水氮互作条件下的2年生银杏幼苗为研究对象,使用数字扫描仪采集银杏幼苗叶片图像,利用数字图像技术构建颜色特征参数,结合相关性分析初筛出对叶绿素显著相关的颜色特征参数,并进一步基于高斯过程回归(gaussian process regression, GPR)和偏最小二乘回归(partial least squares regression, PLSR)优选建模中最为重要的颜色特征参数,建立基于银杏叶片颜色特征参数的叶绿素含量估测模型。结果表明,叶绿素含量随着施氮水平和水分处理水平的上升总体上呈现逐渐提高而后缓慢下降的趋势。基于单一颜色参数建立的单变量回归模型(R^(2)=0.01~0.72)预测精度总体上低于使用高斯过程回归(R^(2)=0.79~0.81)和偏最小二乘法(R^(2)=0.75~0.77)的模型。其中,GPR-BAT模型和PLSR-VIP模型都筛选出了对叶绿素敏感的R、G颜色特征参数;GPR模型的表现总体上优于PLSR模型,特别是在使用GPR-BAT优选颜色参数建模时表现最佳(R^(2)=0.81)。基于GPR-BAT优选颜色参数构建的GPR模型效果最佳,可准确估测银杏叶片叶绿素含量,为银杏生产的精确管理和监测银杏生长状况提供技术支撑。
基金Supported by National Natural Science Foundation of China(Grant Nos51175085,51375094)Fujian Provincial Education Department Foundation of China(Grant No.JA13059)+1 种基金Open Fund of State Key Laboratory of Tribology of Tsinghua University,China(Grant No.SKLTKF13B02)Fuzhou Science and Technology plan Fund of China(Grant No.2014-G-74)
文摘Currently, the approximation methods of the Gaussian filter by some other spline filters have been developed. However, thesc methods are only suitable for the study of one-dimensional filtering, when these methods are used for three-dimensional filtering, it is found that a rounding error and quantization error would be passed to the next in every part. In this paper, a new and high-precision implementation approach for Gaussian filter is described, which is suitable for three-dimensional reference filtering. Based on the theory of generalized B-spline function and the variational principle, the transmission characteristics of a digital filter can be changed through the sensitivity of the parameters （t1, t2）, and which can also reduce the rounding error and quantization error by the filter in a parallel form instead of the cascade form, Finally, the approximation filter of Gaussian filter is obtained. In order to verify the feasibility of the new algorithm, the reference extraction of the conventional methods are also used and compared. The experiments are conducted on the measured optical surface, and the results show that the total calculation by the new algorithm only requires 0.07 s for 480×480 data points; the amplitude deviation between the reference of the parallel form filter and the Gaussian filter is smaller; the new method is closer to the characteristic of the Gaussian filter through the analysis of three-dimensional roughness parameters, comparing with the cascade generalized B-spline approximating Gaussian. So the new algorithm is also efficient and accurate for the implementation of Gaussian filter in the application of surface roughness measurement.
文摘An inequality describing the difference between Gamma and Gaussian distributions is derived. The asymptotic bound is much better than by existing uniform bound from Berry-Esseen inequality.
文摘在运输过程中,包装件经常受到非高斯随机振动的作用,在进行包装系统优化时,经常需要重复确定包装件加速度响应的统计特征和振动可靠性,该研究提出一种高效准确确定非高斯随机振动条件下非线性包装件加速度响应统计特征的分析方法。采用非高斯Karhunen-Loeve展开将非高斯随机振动表示为非高斯随机变量的线性组合,用一阶泰勒展开估计包装件加速度响应,确定加速度响应的统计矩参数,根据包装件加速度响应的前四阶矩参数,应用鞍点估计法确定包装件加速度响应的概率密度函数(probability density function, PDF)和累积分布函数(cumulative distribution function, CDF)。由于采用随机变量的线性组合模拟非高斯随机振动激励,避免了随机变量非线性变换,采用一阶泰勒展开估计包装件加速度响应具有良好的准确性,鞍点估计法分析包装件加速度响应的PDF和CDF,避免了大量蒙特卡洛或拟蒙特卡洛分析,提高了分析效率。
