Iterative regularization method for image denoising with adaptive scale parameter

In order to decrease the sensitivity of the constant scale parameter, adaptively optimize the scale parameter in the iteration regularization model （IRM） and attain a desirable level of applicability for image denoising, a novel IRM with the adaptive scale parameter is proposed. First, the classic regularization item is modified and the equation of the adaptive scale parameter is deduced. Then, the initial value of the varying scale parameter is obtained by the trend of the number of iterations and the scale parameter sequence vectors. Finally, the novel iterative regularization method is used for image denoising. Numerical experiments show that compared with the IRM with the constant scale parameter, the proposed method with the varying scale parameter can not only reduce the number of iterations when the scale parameter becomes smaller, but also efficiently remove noise when the scale parameter becomes bigger and well preserve the details of images.

Vertical Scale Parameter Estimates for 48 Non-edge-on Spiral Galaxies

In the first paper of this series, we directly studied the mathematicalforms, symmetry of spiral structure, and the projection of galactic discs on the images, andmeasured the pitch angles of the spiral arms and inclination angles of the galactic discs for 60spiral galaxies. In this second paper, we estimate the vertical scale parameters of 48 non-edge-onspiral galaxies based on the method proposed by Peng et al. and on the results given in Paper I. Aswe know, for edge-on disc galaxies we can obtain the vertical scale parameter from the photometry,once a mathematical form is specified for the vertical light distribution. For non-edge-on galaxies,some other methods have to be used. The statistical result was that the vertical scale parameter iscomparable for edge-on and non-edge-on galaxies, although it is obtained from two very differentmethods.

Prediction of nonlocal scale parameter for carbon nanotubes

Based on the theory of nonlocal elasticity,a nonlocal shell model accounting for the small scale effect is developed for the bending characteristics of CNTs subjected to the concentrated load.With this nonlocal shell model,explicit expressions are derived for the bending solutions.To extract the proper values of nonlocal scale parameter,we have made molecular dynamics(MD) simulations for various radii and lengths of armchair and zigzag CNTs,the results of which are matched with those of nonlocal continuum model.It is found that the present nonlocal elastic shell model with its appropriate values of nonlocal scale parameter has the capability to predict the bending behavior of CNTs,which is comparable with the results of MD simulations.Moreover,exact closed form solutions for the nonlocal scale parameter for zigzag and armchair CNTs are obtained.The results show that nonlocal scale parameter is independent of the length of CNTs,and dependent on the radius of CNTs.

Scaling parameters selection principle for the scaled unscented Kalman filter

The paper deals with the state estimation of the widely used scaled unscented Kalman filter（UKF）. In particular, the stress is laid on the scaling parameters selection principle for the scaled UKF. Several problems caused by recommended constant scaling parameters are highlighted. On the basis of the analyses, an effective scaled UKF is proposed with self-adaptive scaling parameters,which is easy to understand and implement in engineering. Two typical strong nonlinear examples are given and their simulation results show the effectiveness of the proposed principle and algorithm.

A Simulating Study on Resolvable-Scale Microphysical Parameterization in a Mesoscale Model

The Penn State/ NCAR Mesoscale Model (MM5) is used to simulate the precipitation event that occurred during 1–2 May 1994 to the south of the Yangtze River. In five experiments the Kain–Fritsch scheme is made use of for the subgrid–scale convective precipitation, but five different resolvable–scale microphysical parameterization schemes are employed. They are the simple super-saturation removal scheme, the warm rain scheme of Hsie et al. (1984), the simple ice scheme of Dudhia (1989), the complex mixed–phase scheme developed by Reisner et al. (1993), and the GSFC microphysical scheme with graupel. Our interest is how the various resolvable-scale schemes affect the domain-averaged precipitation, the precipitation distribution, the sea level pressure, the cloud water and the cloud ice. Through a series of experiments about a warm sector rainfall case, results show that although the different resolvable-scale scheme is used, the differences of the precipitation characteristics among all five runs are not very obvious. However, the precipitation is over-predicted and the strong mesoscale low is produced by the simple super-saturation removal scheme. The warm rain scheme with the inclusion of condensation and evaporation under-predicts the precipitation and allows the cloud water to reach the 300 hPa level. The scheme of the addition of graupel increases the resolvable-scale precipitation by about 20%-30%. The inclusion of supercooled liquid water in the grid-scale scheme does not affect significantly the results. Key words Mesoscale model - Precipitation - Resolvable-scale microphysical parameterization

重参数化YOLOv5s的森林火灾检测算法

目前森林火灾多发,建立日常监测尤为重要,但是边缘智能检测设备算力和内存较低,限制了检测模型的推理和部署。针对以上问题,提出一种改进的重参数化YOLOv5s的森林火灾检测算法,结合重参数化、通道重排和深度可分离卷积(Depthwise Separable Convolution,DSC)等轻量化思想分别设计新的骨干和颈部网络,增强特征提取能力,提高模型检测精度,使参数量和推理权重较大幅度减少。为避免颈部网络的信息丢失,根据空洞卷积提出特征增强模块,增强多尺度特征融合能力。为进一步提高模型性能,加入轻量化的CA注意力机制,更准确定位目标。当前公开的火焰烟雾数据集存在针对性不强的问题,为了更好地提高模型的检测效率,制作了一个新的森林火灾数据集,在数据集上利用结构相似性算法剔除了相似度过高的图片,保证了模型的泛化能力。实验结果表明,改进后的重参数化YOLOv5s以原网络约76%的参数量提高了4.0%的精确度,推理权重下降至10.5 MB,更适合于设备性能差、容量小的边缘设备,提高了森林火灾巡检的效率。

利用尺度自适应大气边界层湍流参数化方案对一次陆地浓雾的数值模拟

为提高大气数值模式的模拟能力,改进大气边界层水汽、热量湍流输送计算和大雾天气的模拟效果,选用WRF三维非静力模式,采用具有局地和非局地垂直湍流尺度自适应计算能力的MYNN_SA参数化方案,对2017年12月28—29日我国华北—江淮地区的大范围浓雾过程进行了数值模拟研究,探讨从中尺度到灰区尺度分辨率范围,模式的尺度自适应大气边界层湍流参数化方案对稳定大气边界层发展、湍流输送和大雾天气模拟的影响。利用中国地面气象站观测资料和ERA5再分析数据,在接近灰区尺度的网格分辨率上,利用尺度自适应大气边界层湍流MYNN_SA参数化方案较之中尺度参数化MYNN方案,可明显改善次网格湍流输送计算,以及陆地浓雾的强度、空间分布和时间演变特征,可更精确地模拟云水混合比、逆温层和雾区的垂直结构。

尺度适应重力波拖曳方案在高分辨率数值预报中的应用研究

随着数值模式分辨率越来越高,在复杂地形区域仅考虑高层重力波拖曳作用和地形阻塞作用具有局限性,WRFv4.3模式中新型重力波拖曳方案在原有大尺度重力波拖曳和地形阻塞作用基础上新加入了边界层小尺度重力波拖曳作用,且对湍流地形拖曳作用增加了描述,从而可以达到尺度适应。为了验证新的重力波拖曳方案的效果,本文基于华北区域3 km对流可分辨模式开展了2021年冬季重力波拖曳参数化方案应用试验,对比分析了三组试验方案:不开启重力波拖曳、原有的仅考虑大尺度重力波拖曳和阻塞作用的方案以及新型的尺度适应方案的模拟结果。试验结果表明:原有重力波拖曳方案仅考虑重力波拖曳和大尺度地形阻塞,在3 km模式中对复杂地形附近整层风场影响较大,但是正效果有限;新型尺度适应重力波拖曳方案在3 km分辨率模式中大尺度重力波拖曳和阻塞拖曳作用为0,仅由边界层内小尺度重力波拖曳和湍流地形拖曳起作用,能够达到尺度适应效果;由于高层重力波拖曳为0,开启新型重力波拖曳会降低低空尤其是边界层内风场预报正偏差,对高空风场无影响;对模拟区域的统计检验结果表明,新型重力波拖曳方案可以有效减少地形复杂区域近地面风场预报的误差,但对温度等其它要素的改善有限。

Evaluating and Improving Wind Forecasts over South China: The Role of Orographic Parameterization in the GRAPES Model

Unresolved small-scale orographic（SSO） drags are parameterized in a regional model based on the Global/Regional Assimilation and Prediction System for the Tropical Mesoscale Model（GRAPES TMM）. The SSO drags are represented by adding a sink term in the momentum equations. The maximum height of the mountain within the grid box is adopted in the SSO parameterization（SSOP） scheme as compensation for the drag. The effects of the unresolved topography are parameterized as the feedbacks to the momentum tendencies on the first model level in planetary boundary layer（PBL）parameterization. The SSOP scheme has been implemented and coupled with the PBL parameterization scheme within the model physics package. A monthly simulation is designed to examine the performance of the SSOP scheme over the complex terrain areas located in the southwest of Guangdong. The verification results show that the surface wind speed bias has been much alleviated by adopting the SSOP scheme, in addition to reduction of the wind bias in the lower troposphere. The target verification over Xinyi shows that the simulations with the SSOP scheme provide improved wind estimation over the complex regions in the southwest of Guangdong.

A Quaternion Scaled Unscented Kalman Estimator for Inertial Navigation States Determination Using INS/GPS/Magnetometer Fusion

This Inertial Navigation System (INS), Global Positioning System (GPS) and fluxgate magnetometer technologies have been widely used in a variety of positioning and navigation applications. In this paper, a low cost solid state INS/GPS/Magnetometer integrated navigation system has been developed that incorporates measurements from an Inertial Navigation System (INS), Global Positioning System (GPS) and fluxgate magnetometer (Mag.) to provide a reliable complete navigation solution at a high output rate. The body attitude estimates, especially the heading angle, are fundamental challenges in a navigation system. Therefore targeting accurate attitude estimation is considered a significant contribution to the overall navigation error. A better estimation of the body attitude estimates leads to more accurate position and velocity estimation. For that end, the aim of this research is to exploit the magnetometer and accelerometer data in the attitude estimation technique. In this paper, a Scaled Unscented Kalman Filter (SUKF) based on the quaternion concept is designed for the INS/GPS/Mag integrated navigation system under large attitude error conditions. Simulation and experimental results indicate a satisfactory performance of the newly developed model.

Scaling the Microphysics Equations and Analyzing the Variability of Hydrometeor Production Rates in a Controlled Parameter Space

A set of microphysics equations is scaled based on the convective length and velocity scales. Comparisons are made among the dynamical transport and various microphysical processes. From the scaling analysis, it becomes apparent which parameterized microphysical processes present off-scaled influences in the integration of the set of microphysics equations. The variabilities of the parameterized microphysical processes are also studied using the approach of a controlled parameter space. Given macroscopic dynamic and thermodynamic conditions in different regions of convective storms, it is possible to analyze and compare vertical profiles of these processes. Bulk diabatic heating profiles for a cumulus convective updraft and downdraft are also derived from this analysis. From the two different angles, the scale analysis and the controlled-parameter space approach can both provide an insight into and an understanding of microphysics parameterizations.

A Method Determining Vertical Scaling Parameters of Fractal Interpolation

A method determining vertical scaling parameters of fractal interpolation is given in this paper. By computer experiments, it is clear that this method is very effective.

基于数值模式评估细尺度参数化方案在南大洋背风波生成源地的适用性

验证基于GM(Garret-Munk)大洋内波普适谱的细尺度参数化方案在不同海域的适用性,对于湍流混合研究来说非常重要。包含背景GM内波场的高分辨率数值模式被用于评估细尺度参数化方案在背风波生成源地处的适用性。细尺度参数化方案主要包括基于剪切的G89 (Gregg 1989)方案、基于应变的W93 (Wijesekera 1993)方案、基于剪切和应变的GHP (Gregg-Henyey-Polzin)方案以及对GHP方案中的频率矫正项作出变换的IH (Ijichi-Hibiya)方案。计算结果显示,背风波的生成伴随着海底上方近惯性内波的增强,使得内波场的动能与势能的比值相较于GM内波场偏大。在这种情况下,基于剪切的G89方案会因为高估内波场的总能量而高估耗散率。反之,基于应变的W93方案会因为低估内波场的总能量而低估耗散率。计算结果还显示,已经考虑了内波谱变形的GHP方案仍然会高估耗散率,但IH方案能比较准确地估算耗散率。

青藏高原东北部地区一次强降水过程的灰色尺度积云对流参数化敏感性研究

本文利用WRF(Weather Research and Forecasting)V4.0模式对2016年8月17~18日发生在青藏高原东北部青海省的一次强对流过程开展了3 km高分辨率数值模拟,基于观测小时降水数据、FY-2E卫星资料、探空资料和再分析资料等,通过四组敏感性试验对比分析了在模式对流灰色尺度中使用完全显式方案(EXP试验)、传统参数化方案(KF试验)以及尺度感知参数化方案(Multi-Scale KF;MSKF试验)对对流降水模拟的差异及其影响机制。结果表明:不同的湿物理过程处理对青藏高原地区灰色尺度内对流降水强度和落区的模拟存在较大差异。KF试验模拟的18小时累积降水在降水落区和强度上较EXP和MSKF试验与实况最为接近,这与Kain-Fritsch eta(KFeta)参数化方案在降水中心区域产生的对流性降水对总降水的相对贡献较大有关。而EXP和MSKF试验模拟的降水潜热释放产生的300~400 hPa正位涡(Potential Vorticity;PV)异常,受较强的垂直风切变影响随高度向下游倾斜明显,使得其低层500 hPa正PV异常大值区较KF试验呈现出超前特征,进而导致了下游地区低层的局地风场特征、水汽通量输送及大气稳定度的改变,最终导致强降水落区较KF试验和实况向东北方向(下游)偏移。以上分析表明,在青藏高原灰色尺度内,仍然需要依赖对流参数化方案隐式地描述次网格对流过程来弥补显式方案的模拟偏差;而MSKF方案似乎对该地区的对流描述还存在一些不确定性。

基于结构重参数化的目标检测模型

虽然多尺度感受野特征融合能显著提升目标检测模型的精度,但同时也大大增加了模型的运算成本。针对这一问题,本文提出了基于结构重参数化的目标检测模型。首先,使用深度卷积代替SPP中的最大池化,并利用结构重参数化降低模块运算量,提出了新的感受野特征融合模块CspRepSPP。接着,基于结构重参数化技术,提出了新的特征提取模块RepBottleNeck。实验结果表明,在VOC 2012数据集上,相比原模型YOLOv5s,本文模型在mAP0.5:0.95指标上提升了3.22%,单张图片的推理速度提升了0.5 ms,GFLOPs降低了1.0。与其他YOLOv5s改进算法相比,本文算法检测精度更高,推理速度更快,参数量更低。

Establishment of size-dependant constitutive model of micro-sheet metal materials

The inherent mechanism of size effect in micro-sheet material behavior of plastic forming was explained by the surface layer model and theory of metal crystal plasticity. A size-dependant constitutive model based on the surface layer model was established by introducing the scale parameters and modifying the classical Hall-Petch equation. The influence of the geometric dimensions and the grain size on the flow behavior of the material was discussed using the new material constitutive model. The results show that, the flow stress decreases while the sheet metal thickness decreases when the grain size keeps constant, and the micro-sheet metal with a larger grain size is more easily to be influenced by the size effects. The material constitutive model established is validated by the stress-strain curve of the micro-sheet metal with different thicknesses derived from the tensile experiments. The rationality of the material model is verified by the fact that the calculation results are consistent with the experimental results.

大范围网格曲面曲线设计方法及应用

为了满足齿科在离散网格曲面建模中对曲线设计高效性、鲁棒性及基于网格曲线个性化建模等方面的要求,提出了一种基于局部参数化的离散网格曲面样条曲线设计方法。该方法放松了对样条曲线全局连续性的约束,将平面参数域内的全局样条线设计转化成在局部区域内的分段样条曲线设计,提高了参数化网格曲线设计方法的效率及鲁棒性,使其能够不受编辑范围、网格模型复杂度及网格亏格的影响,满足大范围的网格曲线实时编辑的要求,以及齿科个性化建模软件中基于曲线建模的需求;引入两型值点间的最短路径,解决在样条线设计过程中,因相邻两型值点距离过大而导致算法存在的鲁棒性问题;引入局部光顺算法,在型值点附近进行流行约束下的光顺,提高样条曲线的光滑度。实验表明,基于平面参数化域的局部分段样条曲线设计方法在效率、鲁棒性及实用性方面具有一定的优势,综合性能较好,能够满足齿科建模软件的实际应用需求。

黄土高原陆面过程试验研究(LOPEX)有关科学问题

主要讨论了黄土高原陆面过程野外科学试验研究项目的有关科学技术问题。首先从科学和现实角度说明了开展黄土高原陆面过程试验研究(LOPEX)的意义,并从黄土高原陆面过程野外观测和特征分析、黄土高原陆面水分过程特征及其对生态生理过程的影响、黄土高原陆面过程参数化研究等3个方面介绍了该科学试验研究项目的主要研究内容和重点要解决的科学问题,而且还初步探讨了黄土高原陆面过程试验研究的技术难点以及解决这些技术难点的主要科学技术思路。

中尺度大气模式MM5简介

本文介绍了中尺度非静力大气模式 MM5 的动力框架、模式物理过程计算和参数化方法以及模式系统流程。

翼伞系统最优归航轨迹设计的敏感度分析方法

本文对三自由度翼伞系统归航轨迹优化问题进行了研究,采用控制变量参数化与时间尺度变换相结合的优化算法对翼伞系统的最优控制问题进行数值求解.该方法是基于灵敏度分析的优化算法,将控制量以及控制量转换时间转化为一系列参数优化问题同时进行求解.仿真结果表明,相对于基于两端边值优化算法而言,灵敏度分析法只需要正向积分进行求解,因而具有计算简单、耗时短等优点,其控制效果良好,距离偏差和方向偏差均满足实际需求,有效地提高了翼伞系统的着陆精度,验证了该优化算法的可行性.