指数混合模型非线性最小二乘法的参数分辨率探讨

文章以两分量指数衰减模型为例,给出求解模型参数非线性最小二乘法分辨率的定义。为衡量此类相近信号能否分开提供一个标准,也为评价非线性最小二乘法在估计此模型准确度的度量提供一个新方法。实验表明:信噪比越大,参数分辨率精度越高;均匀取点比均匀对数取点得到更好的参数估计;固定信噪比时,在合适样本区间和样本数量下,局部分辨率与整体分辨率是一致的;参数分辨率与噪声的四分之一次方满足正线性关系。

线性回归模型参数估计方法的分辨率

为给出算法对一般参数的区分能力,提出参数分辨率的概念.该文结合聚类思想,给出参数分辨率的定义和计算方法,并分别用最小二乘法与全最小一乘法对一元线性回归模型进行参数分辨率分析.实验结果表明两种算法均具有性质:参数分辨率的精度随信噪比的增大而增大;局部参数分辨率与整体参数分辨率保持一致;噪声的标准差与最小二乘参数分辨率满足线性关系,并利用区间估计理论给出证明.最后,对两段相似的音频信号,分别采用最小二乘法和全最小一乘法进行参数分辨率分析,实验结果表明了参数分辨率概念的合理性和有效性.参数分辨率是衡量两个相近信号能否被分开的一个标准,是评价模型及算法准确度的有效指标.

自适应通道均衡在MUSIC空间谱及分辨率中的应用

高分辨率参数估计算法MUSIC对系统误差比较敏感。文中分析了接收阵元间通道失配对MUSIC空间谱的影响。

多分辨率增强能量算子的轴承微弱故障特征提取

Teager能量算子(Teager Energy Operator,简称TEO)可通过计算信号能量的方式凸显信号中的瞬态信息,在轴承故障诊断中的应用极为广泛。然而,TEO处理低信噪比信号时,其性能明显下降。针对该问题,提出引入多分辨率参数,用于机车轴承微弱故障特征提取。设置多分辨率参数m构造多分辨率Teager能量算子(Multiresolution Teager Energy Operator,简称MTEO);利用MTEO计算信号总能量获得信号能量谱,从信号能量的角度消除噪声、增强故障信息;对能量谱包络谱分析获得诊断结果。仿真数据、实验室数据和工程数据验证了该方法的有效性,通过与TEO方案对比,表明MTEO方法能够改善TEO的应用效果,提升轴承微弱故障识别率。

Practical Model of Sea Ice Thickness of Bohai Sea Based on MODIS Data

Sea ice thickness is one of the most important input parameters in the studies on sea ice disaster prevention and mitigation. It is also the most important content in remote sensing monitoring of sea ice. In this study, a practical model of sea ice thickness(PMSIT) was proposed based on the Moderate Resolution Imaging Spectroradiometer(MODIS) data. In the proposed model, the MODIS data of the first band were used to estimate sea ice thickness and the difference between the second-band reflectance and the fifth-band reflectance in the MODIS data was calculated to obtain the difference attenuation index(DAI) of each pixel. The obtained DAI was used to estimate the integrated attenuation coefficient of the first band of the MODIS at the pixel level. Then the model was used to estimate sea ice thickness in the Bohai Sea with the MODIS data and then validated with the actual sea ice survey data. The validation results showed that the proposed model and corresponding parameterization scheme could largely avoid the estimation error of sea ice thickness caused by the spatial and temporal heterogeneity of sea ice extinction and allowed the error of 18.7% compared with the measured sea ice thickness.

A new self-adaptive remeshing approach

This paper proposes a self-adaptive approach to converting irregular genus-O meshes into those with subdivision connectivity. To assure a maximal utilization of the multiresolution techniques on the remesh, we map the original mesh onto the unit sphere and construct a base mesh with only four vertices. We also introduce a self-adaptive relocation operation, which is used to adapt the vertex distribution of the spherical subdivision mesh to that of the parameterized mesh, to improve the visual appearance of the remesh. The experimental results show that our method can not only make the number of irregular vertices in the remesh as small as possible, but also preserve the details of the original mesh well.

Modeling All-sky Global Solar Radiation Using MODIS Atmospheric Products:A Case Study in Qinghai-Tibet Plateau

The surface solar radiation(SSR) is of great importance to bio-chemical cycle and life activities.However,it is impossible to observe SSR directly over large areas especially for rugged surfaces such as the Qinghai-Tibet Plateau.This paper presented an improved parameterized model for predicting all-sky global solar radiation on rugged surfaces using Moderate Resolution Imaging Spectroradiometer(MODIS) atmospheric products and Digital Elevation Model(DEM).The global solar radiation was validated using 11 observations within the plateau.The correlation coefficients of daily data vary between 0.67-0.86,while those of the averages of 10-day data are between 0.79-0.97.The model indicates that the attenuation of SSR is mainly caused by cloud under cloudy sky,and terrain is an important factor influencing SSR over rugged surfaces under clear sky.A positive relationship can also be inferred between the SSR and slope.Compared with horizontal surfaces,the south-facing slope receives more radiation,followed by the west-and east-facing slopes with less SSR,and the SSR of the north-facing slope is the least.

New Mathematical Model Based on Affine ransformation for Remote Sensing Image with High Resolution

This paper calculates the parameters of image position and orientation,proposes a mathematical model and adopts a new method with three steps of transformations based on parallel ray projection.Every step of the model is strict,and the map function of each transformation is the first order polynomials and other simple function.The final calculation of the parameters is for the linear equations with good status.As a result,the problem of the relativity of image parameter calculation is solved completely.Some experiments are carried out.

IMPACTS OF CUMULUS PARAMETERIZATION AND RESOLUTION ON THE MJO SIMULATION

Madden-Julian Oscillations (MJO) in six integrations using an AGCM with different cumulus parameterization schemes and resolutions are examined to investigate their impacts on the MJO simulation. Results suggest that the MJO simulation can be affected by both resolution and cumulus parameterization, though the latter, which determines the fundamental ability of the AGCM in simulating the MJO and the characteristics of the simulated MJO, is more crucial than the former. Model resolution can substantially affect the simulated MJO in certain aspects. Increasing resolution cannot improve the simulated MJO substantially, but can significantly modulate the detailed character of the simulated MJO; meanwhile, the impacts of resolution are dependent on the cumulus parameterization, determining the basic features of the MJO. Changes in the resolution do not alter the nature of the simulated MJO but rather regulate the simulation itself, which is constrained by cumulus parameterization schemes. Therefore, the vertical resolution needs to be increased simultaneously. The vertical profile of diabatic heating may be a crucial factor that is responsible for these different modeling results. To a large extent, it is determined by the cumulus parameterization scheme used.

Numerical Analysis of the Biogeochemical Parameters in the Bay of Bengal

Oceanic nutrient cycling plays a key role in understanding how oceanic biogeochemical parameters respond in varying physical and anthropogenically controlled processes. OA （Objective Analysis） of monthly climatology of WOAI3 （World Ocean Atlas 13） nutrient data of 5 km resolution called Nutrient-Climo has been done in this paper for analyzing the nutrient-rich region in the BOB （Bay of Bengal） and the mechanisms of physical forces were examined using six years （2002-2007） global ocean monthly analysis datasets based on the SODA v2.0.4 （Simple Ocean Data Assimilation package）. The upwelled zones established from the circulation pattern were well synchronized with the nitrate rich zones. The POC （particulate organic carbon） of 5 km resolution has been analyzed from MODIS （Moderate-resolution Imaging Spectroradiometer） data and Chl a （Chlorophyll a） concentration SeaWiFS （Sea-viewing Wide Field-of-view Sensor） data of 9 km resolution are used to predict the productive zones in the BOB. In this paper, we examined that Chl a concentration （above 0.5 mg/m3） is found during the post-monsoon followed by winter in the north-western, north-eastern coast and head BOB as the source of nutrients is also supplementary due to high input of litter and sediment associated nutrients that are released during estuarine transport.

异方差问题伪检验研究

研究目标:探讨异方差相关的伪检验及参数可分辨问题。研究方法:运用理论分析和蒙特卡洛仿真方法。研究发现:同方差或异方差情形使用错误异方差的WLS的假设检验是错误的,易导致伪回归,常比直接使用OLS更糟;异方差时虽估计是一致的,即使大样本也不可直接使用OLS进行假设检验,因得到伪回归或将显著参数误判为不显著的可能性不会随样本增大而改善;稳健方差估计可得到OLS实际方差的较好估计,对原假设误判通常无影响,但参数分辨力变差,检验功效明显下降;WLS的BLUE性很不稳健,只识别出引起异方差的变量而不了解其完整结构没有意义。研究创新:推导出参数分辨率公式,发现避免异方差伪检验的思路。研究价值:为正确评价存在异方差的模型提供了有益的建议。

Inertial gravity wave parameters for the lower stratosphere from radiosonde data over China

Characterization of gravity wave （GW） parameters for the stratosphere is critical for global atmospheric circulation models. These parameters are mainly determined from measurements. Here, we investigate variation in inertial GW activity with season and latitude in the lower stratosphere （18-25 km） over China, using radiosonde data with a high vertical resolution over a 2-year period. Eight radiosonde stations were selected across China, with a latitudinal range of 22°-49°N. Analyses show that the GW energy in the lower stratosphere over China has obvious seasonal variation and a meridional distribution, similar to other regions of the globe. The GW energy is highest in winter, and lowest in summer; it decreases with increasing latitude. Velocity perturbations with longitude and latitude are almost the same, indicating that GW energy is horizontally isotropic. Typically, 85% of the vertical wavelength distribution is concentrated between elevations of 1 and 3 km, with a mean value of 2 kin; it is almost constant with latitude. Over 80% of all the horizontal wavelengths occur in the range 100-800 km, with a mean value of 450 km; they show a weak decrease with increasing latitude, yielding a difference of about 40 km over the 22°-49°N range. The ratio of horizontal wavelength over vertical wavelength is about 200：1, which implies that inertial GWs in the lower stratosphere propagate along nearly horizontal planes. Ratios of their intrinsic frequency to the Coriolis parameter decrease with increasing latitude; most values are between 1 and 2, with a mean value of 1.5. Study of the propagation directions of GW energy shows that upward fractions account for over 60% at all stations. In contrast, the horizontal propagation direction is significantly anisotropic, and is mainly along prevailing wind directions; this anisotropy weakens with increasing latitude.