Analysis of reflected signal of quad rotor UAV based on model fitting in mobile communication system

In view of the many scenes of unmanned aerial vehicle(UAV)detection,a third-party signal source is used to design a receiver to monitor the UAV.It is of great significance to understand the reflection of the signal illuminating the UAV.Taking the communication base station(BS)signal as the third-party signal source,and considering the complete transmission link,reflection changes and loss fading of the communication signal,this study conducts model fitting for irregular UAV targets,simplifying complex targets into a combination of simple targets.Furthermore,the influence of the dielectric constant of the target surface and the signal irradiation angle on the signal reflection is analyzed.The analysis shows that the simulation results of this model fitting method are consistent with the results of other literature,which provides theoretical support for the detection of low and slow small targets such as UAVs.

Objective Fitting Evaluation Model for Dressing Fit Based on Wrinkle Index of Dressing Image

An effective model(image to wrinkle, ITW) for garment fitting evaluation is presented. The proposed model is to improve the accuracy of garment fitting evaluation based on dressing image. The ITW model is an objective evaluation model of fitting based on the wrinkle index of dressing image. The ITW model consists of two main steps, the gray curve-fitting(GCF) threshold segmentation algorithm and Canny edge detection algorithm. In the ITW model, three types of wrinkle trends are defined. And the network dressing image is evaluated and simulated by three quantitative indexes: wrinkle number, wrinkle regularity and wrinkle unevenness. Finally, the fitness of three kinds of dress effects(tight, fit and loose) is quantified by objective fitting evaluation model.

Numerical Tidal Current Modeling Using Fine Boundary-Fitted Grids for Tidal Flats

Fine grids with small spacing in boundary-fitted coordinates are normally used to treat the computation of fluid dynamics for estuarine areas and tidal flats. However, the adoption of Cartesian components of velocity vectors in this kind of non-orthogonal coordinates will definitely result in a difficulty in solving implicitly the transformed momentum equations, and also complicate the wet-dry point judgement used for flood areas. To solve this problem, equations in terms of generalized contravariant velocity vectors in curvilinear coordinates are derived in the present study, by virtue of which, an Alternative-Direction-Implicit numerical scheme in non-orthogonal grids would then be easily obtained, and wet-dry point judgement would as well be largely simplified. A comparison is made between the explicit scheme and implicit scheme, showing that the present model is accurate and numerically stable for computations of fluid dynamics for estuarine areas and tidal flats.

Comprehensive two-dimensional river ice model based on boundary-fitted coordinate transformation method

River ice is a natural phenomenon in cold regions, influenced by meteorology, geomorphology, and hydraulic conditions. River ice processes involve complex interactions between hydrodynamic, mechanical, and thermal processes, and they are also influenced by weather and hydrologic conditions. Because natural rivers are serpentine, with bends, narrows, and straight reaches, the commonly-used one-dimensional river ice models and two-dimensional models based on the rectangular Cartesian coordinates are incapable of simulating the physical phenomena accurately. In order to accurately simulate the complicated river geometry and overcome the difficulties of numerical simulation resulting from both complex boundaries and differences between length and width scales, a two-dimensional river ice numerical model based on a boundary-fitted coordinate transformation method was developed. The presented model considers the influence of the frazil ice accumulation under ice cover and the shape of the leading edge of ice cover during the freezing process. The model is capable of determining the velocity field, the distribution of water temperature, the concentration distribution of frazil ice, the transport of floating ice, the progression, stability, and thawing of ice cover, and the transport, accumulation, and erosion of ice under ice cover. A MacCormack scheme was used to solve the equations numerically. The model was validated with field observations from the Hequ Reach of the Yellow River. Comparison of simulation results with field data indicates that the model is capable of simulating the river ice process with high accuracy.

Asymptomatic Distribution of Goodness-of-Fit Tests in Logistic Regression Model

The logistic regression model has been become commonly used to study the association between a binary response variable;it is widespread application rests on its easy application and interpretation. The subject of assessment of goodness-of-fit in logistic regression model has attracted the attention of many scientists and researchers. Goodness-of-fit tests are methods to determine the suitability of the fitted model. Many of methods proposed and discussed for assessing goodness-of fit in logistic regression model, however, the asymptotic distribution of goodness-of-fit statistics are less examine, it is need more investigated. This work, will focus on assessing the behavior of asymptotic distribution of goodness-of-fit tests, also make comparison between global goodness-of-fit tests, and evaluate it by simulation.

Modelling Three-Dimensional Winds on a NW Pacific Region of Mexico Using Boundary-Fitted Grids

In this study, the momentum equations describing an atmospheric flow over a NW Pacific region of Mexico are solved numerically. In order to capture the complex flow-topography interactions with detail, a combination of a numerical wind model in full 3D curvilinear coordinates, along with a high resolution boundary-fitted grid is used. Boundary conditions were obtained from ten years (2002-2012) of measured offshore wind data. Prevailing winds from April to September during that period of observations were selected for the simulations. For the cases analyzed, it was found that at the points of the study region (PSS, PSM, PM), wind speed increased about 10% to 20% of its offshore values, while inland they decreased about 86% to 96%. This spatial behavior agreed very well with the observed local winds. A coastal jet (CJ), 35 km long with speeds about 1.5 - 2 m/s, emanating from PSS was found for NNW winds. Modeled winds were also used to compute wind stresses, wind stress curl, and CUI fields. Wind stress values agreed very well to those reported in the literature. High values of wind stress curl, and CUI were found at the lee of the points (PSS, PSM, PM). Indirect estimations of sea surface currents were about 15 - 20 cm/s offshore and 5 - 10 cm/s at the coast.

Least squares fitting of coordinate parameters model

This paper starts with untime-diversification of the time-diversification deformation model and gives displacement distribution model of untime-diversification and simplifies further the study of deformation model. The paper discusses the problem of least squares fitting of coordinate parameters model—parameters of deformation model. During discussion, the basic means of cubic B splines and two steps of multidimensional disorder datum fitting are adopted which can make fitting function calculated mostly approximate coordinate parameters model and it can make calculation easier.

湖北襄阳地区土体剪切波波速与深度的相关性研究

为给出湖北襄阳地区典型粘性土、粉土、砂土及碎石土剪切波波速与深度之间的统计公式,基于收集到的102个实测钻孔波速资料,利用多种一元回归模型对襄阳地区常见土层剪切波波速与深度之间的关系进行拟合分析和相关性研究;同时,讨论土体状态对二者关系的影响;最后,利用实测钻孔数据验证统计公式的合理性和可靠性。研究结果表明:1)除人工填土外,襄阳地区其他常规土类剪切波波速与深度之间存在较强的相关性,且离散程度随深度的增加而增大;2)同一土类随密实度或塑性状态的增大,其平均剪切波波速也变大;3)考虑土体状态可以使回归模型的预测结果更加具体、更接近真实值,但对模型拟合优度的变化具有不确定性;4)区域性对土层剪切波波速与深度的统计关系有较大影响。本文研究的襄阳地区各土类剪切波波速回归模型较全国土类模型具有更好的预测精度和误差平稳性,可为南襄盆地及周边区域地震灾害风险普查、场地土动力学性质研究和地震动参数确定等提供参考。

基于2D人体图像特征学习的女西装合体性判别

为解决服装远程定制和网络购衣过程中服装合体性无法预先判断的问题,文章提出利用2D人体图像判断女西装合体性。首先采集了462名18~25周岁青年女性的2D图像及3D尺寸,建立人体数据集。并制作10件虚拟女西装,建立服装数据集。其次提取用于女西装合体性判别的服装特征、2D人体图像关键点距离特征和整体特征。基于感性工学原理,采用专家评价法获取女西装合体性评价标签。最后利用贝叶斯分类器建立女西装合体性判别模型。研究结果显示,将文章提出的特征应用于基于贝叶斯算法的女西装合体性判别模型判别准确率可达到84.8%,说明提出的服装合体性评价指标有效,可以用于基于2D图像的服装合体性预测。

基于自适应AR模型巡航飞行参数预测研究

为更准确实现飞行参数趋势预测,提出一种基于自适应自回归(AR)模型的稳定巡航飞行参数预测方法。根据稳定巡航参数筛选条件,获取建模所需飞行参数。利用卡尔曼滤波原理估计AR模型参数,并与飞行参数构建系统方程,利用无迹卡尔曼滤波实时更新、修正AR模型参数估计值,将自适应AR模型的预测值与曲线拟合模型和灰色模型的预测值进行对比。以波音B777-300ER飞机的快速存取记录器数据样本进行仿真验证,结果表明:自适应AR模型在数据预测和收敛速率方面均更优,可有效降低预报模型随步数增加导致的精度误差,提高参数预测准确性。研究在飞机维修保障、状态监控与预测等方面具有重要作用。

认知诊断评价中的被试拟合研究

通常情况下,认知诊断需要通过认知诊断模型对被试进行诊断评价。认知诊断模型所生成诊断结果的有效性依赖于被试作答反应是否与所选用的模型拟合。因此,在对诊断结果进行评估的时候,需要通过被试拟合分析来对被试个体的作答反应与模型的拟合情况进行检验,以避免错误或无效的补救措施。本研究基于加权的得分残差,提出认知诊断评价中新的被试拟合指标R。模拟研究结果表明,R指标的一类错误率有较好的稳定性,对随机作答、疲劳、睡眠和创造性作答四种异常被试类型均有较高的统计检验力。并将R指标应用于分数减法实证数据,展示指标在实际测验中的使用过程。

智能手机GNSS数据质量分析与随机模型建立

为提高移动智能终端定位精度,利用小米8和华为Mate20手机采集多个卫星系统的观测数据并进行质量分析,通过不同卫星系统的伪距残差分别对信噪比模型参数进行估计,最后进行静态伪距单点定位实验。结果表明,手机端观测的BDS和GPS伪距精度接近,且高于GLONASS;相较于高度角,伪距残差与信噪比的相关性更强;在信噪比模型参数估计中,小米8拟合效果优于华为Mate20,BDS拟合效果差于其他卫星系统;参数拟合后的信噪比模型在水平和高程方向的定位精度分别为2.37 m和8.38 m,相较于高度角模型,定位精度提升约10%。

区块链赋能全民健身公共服务供给治理研究

运用文献资料法,探究区块链赋能全民健身公共服务供给治理的理论框架、变革向度及精准路径。研究认为:基于“服务金三角”理论模型构建全民健身公共服务供给治理框架,从服务需求重构、供给战略重构、供给系统重构、供给主体重构等方面诠释变革向度。并提出建构“链式”管理、“公有链”运作平台、需求精准管理和供给科学决策、创新赋能机制的供给实践框架,从供给需求、供给战略、供给系统、供给主体层面阐释区块链嵌入供给治理风险,为规避风险提出政府、企业、社会、个体应对路径。

基于van Genuchten模型土壤水分特征曲线的vanfit和MATLAB软件模拟研究

研究了土壤水分特征曲线对探讨土壤水分运动机理及溶质运移动力学机制具有重要科学意义。由于测定土壤水分特征曲线的长历时性和时间限制,在从相关参考文献中提取土壤水分特征曲线测定数据的基础上,建立土壤水分特征曲线的资料库,采用van Genuchten模型对土壤水分特征曲线进行描述,分别应用vanfit软件和MATLAB软件下的lsqcurvefit函数2种方法对土壤进行van Genuchten模型下的4个参数拟合分析。结果表明,2个程序拟合结果大体相近且优良,均方差较小,拟合曲线大致相同,且土壤质地不同,其土壤水分特征曲线差别较大。

基于Delft3D的珠江前航道尸体模型漂移轨迹预测

为预测珠江前航道中尸体的漂移轨迹,帮助当地水警确定溺亡者尸体的具体位置,利用Delft3D构建珠江前航道水动力模型,并使用尸体模型进行了多次现场漂移试验。通过对珠江前航道表层流速进行拟合,建立了尸体模型漂移的预测模型,R^(2)为0.88。研究结果表明,珠江前航道释放的尸体模型受潮汐和径流作用沿河道做往复运动,并呈逐渐漂向下游的趋势;漂移模型验证中尸体模型的漂移速度和方向基本与潮流一致,模拟结果的误差在1 km以内,终点距离误差率小于15%;实例验证中成年女性尸体的模拟结果误差约为300 m;游船所引起的波浪力等外力导致漂移轨迹呈现出南北方向性的偏差,需要进一步提升模拟效果。该漂移模型的推导模式同样适用于其他感潮河段,可使尸体的漂移轨迹变得可测,为尸体打捞工作和警方的案件处理提供了便利和参考。

水稻群体分蘖动态模型构建与应用

为定量分析水稻群体茎蘖数量动态变化过程及分蘖动态特征,该研究使用双Logistic模型分别描述分蘖发生与死亡过程,建立水稻群体分蘖动态模型;根据水稻分蘖过程的时序特征定义描述分蘖过程的特征指标,并推导出分蘖特征指标的计算式;基于不同基因型品种的种植方式、种植时期、种植密度下水稻分蘖动态数据集检验模型优度和适应性;并应用分蘖动态模型和指标探索分蘖动态对种植密度的响应规律。结果表明,所建模型对不同基因型水稻品种在不同种植方式、种植时期和种植密度下的分蘖动态数据拟合优度较好,标准均方根误差S_(RMSE)服从均值小于5%的Gamma分布,并且99%的S_(RMSE)小于10%。基于所建模型计算的分蘖特征指标(包括模型参数)对种植密度有很好的响应;留一法检验表明模型的预测性较好,观测值与模拟值的R^(2)=0.96。所建模型能够精确描述水稻茎蘖数量演变过程,具有很好的拟合优度、适应性和可解释性,可用于分析基因、环境、农艺措施对分蘖动态的影响,分蘖特征指标可望成为分析基因与环境互作的重要表型参数,对指导水稻精准栽培也有重要理论价值和实际意义。

考虑含水率变化的路基压实填料介电特性试验研究

研究介电特性是路基电磁法无损检测技术的基础,为分析路基填料介电特性及其与含水率关系,采用TDR测试砂土、黏性土、改良土、盐渍土等6种典型填料在不同压实度、含水率状态下的介电常数。结果表明:压实填料的介电常数主要受含盐量、含水率、土质类型、压实度等影响;一般路基填料的介电常数主要受控于含水率,压实度在90.0%~96.0%变化时对填料的介电常数影响不显著;一般黏性土、砂性土、改良土的含水率-介电常数关系采用Alharathi模型拟合可满足工程应用精度要求;不同压实度下的Alharathi模型参数较为接近,a=0.100~0.140、b=-0.270~-0.140;掺灰改良土不同压实度的拟合参数差别较大,实际应用中应考虑掺灰比及压实度对介电常数-含水率关系模型的影响。

兼顾型高绩效工作系统的组态效应研究:一个链式中介模型

既有研究中,关于多导向实践的兼顾型高绩效工作系统(HPWS)尚在起步阶段,且其构成与内部交互效应的研究也较为缺乏。本研究基于工作要求—资源理论从组态视角探讨了兼顾型HPWS的承诺型与控制型子系统交互而成的不同组态对员工工作倦怠的影响,以及工作重塑和个人—工作匹配的链式中介作用。基于493份两个时点的纵向数据分析发现,承诺型子系统和控制型子系统对工作倦怠有不同影响,进而兼顾型HPWS的不同组态对工作倦怠的影响存在显著差异,并识别出有效组态(高承诺—高控制、高承诺—低控制)和无效组态(低承诺—高控制、低承诺—低控制),得出影响效果的排序;工作重塑和个人—工作匹配在上述关系间均表现出部分中介作用,并且存在以工作重塑和个人—工作匹配为中介变量的链式中介路径。

黑龙江省樟子松人工林林分直径结构模型的建立

樟子松是中国北方的主要造林树种之一,具有抗寒、抗旱和环境适应性较强等优点。以樟子松人工林为研究对象,采用佳木斯市孟家岗林场6块不同龄组的固定样地数据,分析了樟子松人工林直径分布规律,建立了径阶和累积株数之间的关系模型,通过各种指标以及置信椭圆F检验进行了模型的检验。结果表明:(1)相同立地条件下,樟子松人工林的直径符合正态分布,接近平均直径处的林木株数最多,向两侧逐渐减少。(2)逻辑斯蒂方程可以较好拟合直径分布规律,各样地相关指数R^(2)都大于0.99,实测数据基本都分布在拟合曲线附近。(3)拟合模型通过0.05显著水平下的F检验,林木的累积株数实测值和预测值之间的差异不显著,模型拟合效果较好,具有良好的合理性和适用性。

低幅构造识别技术研究与应用

针对滨里海盆地东缘阿克若尔构造带低幅度构造识别的问题,开发基于反演层速度法和构造趋势面拟合法的低幅构造识别方法。该方法适用于局部发育速度异常体、速度变化快、斜坡区目的层埋藏深度大且圈闭幅度小的情况;优选构造解释层位趋势和单井速度约束下的层速度反演的方法建立研究区速度模型,对地震层位进行标定,克服了常规层速度反演方法横向连续性的限制,对复杂地层具有更好的适应性;构造趋势面拟合法对研究区低幅构造进行有效识别,克服了因构造幅度低、同相轴平直并且变化幅度小而难以识别的问题,对滨里海东缘深度域构造图进行构造趋势面拟合,取得了较好的效果。