Monte Carlo Method for the Uncertainty Evaluation of Spatial Straightness Error Based on New Generation Geometrical Product Specification

Straightness error is an important parameter in measuring high-precision shafts. New generation geometrical product speeifieation（GPS） requires the measurement uncertainty characterizing the reliability of the results should be given together when the measurement result is given. Nowadays most researches on straightness focus on error calculation and only several research projects evaluate the measurement uncertainty based on ＂The Guide to the Expression of Uncertainty in Measurement（GUM）＂. In order to compute spatial straightness error（SSE） accurately and rapidly and overcome the limitations of GUM, a quasi particle swarm optimization（QPSO） is proposed to solve the minimum zone SSE and Monte Carlo Method（MCM） is developed to estimate the measurement uncertainty. The mathematical model of minimum zone SSE is formulated. In QPSO quasi-random sequences are applied to the generation of the initial position and velocity of particles and their velocities are modified by the constriction factor approach. The flow of measurement uncertainty evaluation based on MCM is proposed, where the heart is repeatedly sampling from the probability density function（PDF） for every input quantity and evaluating the model in each case. The minimum zone SSE of a shaft measured on a Coordinate Measuring Machine（CMM） is calculated by QPSO and the measurement uncertainty is evaluated by MCM on the basis of analyzing the uncertainty contributors. The results show that the uncertainty directly influences the product judgment result. Therefore it is scientific and reasonable to consider the influence of the uncertainty in judging whether the parts are accepted or rejected, especially for those located in the uncertainty zone. The proposed method is especially suitable when the PDF of the measurand cannot adequately be approximated by a Gaussian distribution or a scaled and shifted t-distribution and the measurement model is non-linear.

PROBABILISTIC ANALYSIS AND MONTE CARLO SIMULATION OF THE KINEMATIC ERROR IN A SPATIAL LINKAGE

The stochastic models of the usual joints are first established through intro-ducing the concepts of“clearance characteristic element”and“clearance space”.After de-riving the probability density function of the joint clearance and making the probabilisticanalysis of the resulted kinematic errors,the sampling formulas of the independent varia-bles of the joint clearances are further deduced.Through Monte Carlo simulation,the sta-tistical characteristics and frequency histograms of the kinematic errors are then analysedon computer.

Geometric Approximation Searching Algorithm for Spatial Straightness Error Evaluation

Considering the characteristics of spatial straightness error, this paper puts forward a kind of evaluation method of spatial straightness error using Geometric Approximation Searching Algorithm (GASA). According to the minimum condition principle of form error evaluation, the mathematic model and optimization objective of the GASA are given. The algorithm avoids the optimization and linearization, and can be fulfilled in three steps. First construct two parallel quadrates based on the preset two reference points of the spatial line respectively;second construct centerlines by connecting one quadrate each vertices to another quadrate each vertices;after that, calculate the distances between measured points and the constructed centerlines. The minimum zone straightness error is obtained by repeating comparing and reconstructing quadrates. The principle and steps of the algorithm to evaluate spatial straightness error is described in detail, and the mathematical formula and program flowchart are given also. Results show that this algorithm can evaluate spatial straightness error more effectively and exactly.

A MODIFIED EDGE-ORIENTED SPATIAL INTERPOLATION ALGORITHM FOR CONSECUTIVE BLOCKS ERROR CONCEALMENT

This paper proposes a low-complexity spatial-domain Error Concealment (EC) algorithm for recovering consecutive blocks error in still images or Intra-coded (I) frames of video sequences. The proposed algorithm works with the following steps. Firstly the Sobel operator is performed on the top and bottom adjacent pixels to detect the most likely edge direction of current block area. After that one-Dimensional (1D) matching is used on the available block boundaries. Displacement between edge direction candidate and most likely edge direction is taken into consideration as an important factor to improve stability of 1D boundary matching. Then the corrupted pixels are recovered by linear weighting interpolation along the estimated edge direction. Finally the interpolated values are merged to get last recovered picture. Simulation results demonstrate that the proposed algorithms obtain good subjective quality and higher Peak Signal-to-Noise Ratio (PSNR) than the methods in literatures for most images.

基于误差幅空特性分析的空间负荷预测误差评价方法

对空间负荷预测误差进行有效评价是客观认识预测结果,指导预测结果合理应用的前提。然而,现有空间负荷预测误差评价的研究存在对误差的空间分布不考虑或考虑不充分导致评价不准确的问题。为此,提出一种基于误差幅空特性分析的空间负荷预测误差评价方法。首先,从空间负荷预测误差幅值大小和空间分布对电网规划影响的角度出发,对误差的幅空特性进行详细分析;其次,利用运输问题的数学模型来表征正负误差的幅空抵消特性,使用各空间邻近度–幅值误差值曲线与x轴围成面积之和来表征剩余未抵消误差的幅空叠加特性;然后,分别通过伏格尔法和各梯形面积累加公式来计算正负误差的幅空抵消影响值和剩余未抵消误差的幅空叠加影响值,并在此基础上构建空间负荷预测误差评价指标;最后,基于误差对电网规划的实际影响给出对误差评价指标性能的检验方法。算例分析表明,与传统方法相比,该文所提误差评价方法从幅值和空间两个维度实现了对空间负荷预测误差更为全面的评估,与误差对电网规划影响的实际情况贴近度更高。

A Calculation Method of Profile Error Influenced by Tool Error for Two-Axis Coordinated CNC Machining of a Spatial Barrel-Cam

Taking the CNC machining for the spatial barrel-cam with rectilinear translating and a conical roller follower as an example, the calculation method and the law of the profile error influenced by the tool error is given.

空间外差遥感数据光谱-干涉图双向校正算法研究

空间外差光谱技术(SHS)作为新型高光谱分析技术,被广泛应用于大气检测、卫星遥感等领域,但由于空间外差光谱仪的制作不理想或工作环境的变化都会改变仪器参数而引入误差,使干涉图数据不准确,需要进行误差校正。在卫星平台下,由于与地面环境的巨大差异,导致地面测定的校正参数对空间外差干涉图数据不再适用,特别是调制项误差(相位误差和非均匀误差)的改变,极大影响了光谱的准确性。针对空间外差遥感数据的调制项误差,从光谱与干涉图两个方面入手,进行误差分离与原因分析,认为空间外差遥感数据误差主要来源于CCD尺寸伸缩导致的光谱频率变化和CCD响应改变导致的干涉图强度变化,提出了光谱-干涉图双向校正方法。校正测试数据选取高分五号搭载检测仪(GMI)实测的12条O 2吸收光谱。取其中一条作为标定光谱,以SCIATRAN仿真的无误差光谱为基准,与标定光谱进行对比,分析两者在光谱维的频率偏差,通过特征峰频率确定两者的频率变换关系。然后根据变换关系将仿真光谱进行频率拉伸,使拉伸后的仿真光谱与实测光谱谱峰重合,计算拉伸仿真光谱与实测光谱干涉图,将两者干涉图相比得到干涉图强度的变化关系。最后将干涉图强度变化关系用于其余11条光谱的校正,得到校正后光谱。为了衡量校正效果,以校正前后光谱的标准差、均方误差和信噪比作为评价指标。结果显示标准差、均方误差都明显降低,同时信噪比显著增大,且标准差基本都在0.07以下,信噪比基本能达到20以上。其中校正效果最好的实测光谱,标准差减少了0.3767,信噪比提高了25.1016,均方误差降低了0.1587,校正效果较差的实测光谱,标准差减少了0.2296,信噪比提高了9.6328,均方误差降低了0.1049。因此所提出的光谱-干涉图双向校正方法对空间外差遥感数据的误差校正起到较好的效果,且处理过程简单,为同类数据的处理提供了一种新思路。

Spatial Image Watermarking by Error-Correction Coding in Gray Codes

In this paper, error-correction coding (ECC) in Gray codes is considered and its performance in the protecting of spatial image watermarks against lossy data compression is demonstrated. For this purpose, the differences between bit patterns of two Gray codewords are analyzed in detail. On the basis of the properties, a method for encoding watermark bits in the Gray codewords that represent signal levels by a single-error-correcting (SEC) code is developed, which is referred to as the Gray-ECC method in this paper. The two codewords of the SEC code corresponding to respective watermark bits are determined so as to minimize the expected amount of distortion caused by the watermark embedding. The stochastic analyses show that an error-correcting capacity of the Gray-ECC method is superior to that of the ECC in natural binary codes for changes in signal codewords. Experiments of the Gray-ECC method were conducted on 8-bit monochrome images to evaluate both the features of watermarked images and the performance of robustness for image distortion resulting from the JPEG DCT-baseline coding scheme. The results demonstrate that, compared with a conventional averaging-based method, the Gray-ECC method yields watermarked images with less amount of signal distortion and also makes the watermark comparably robust for lossy data compression.

Enhancement of Error-Correction Coding of Spatial Watermarks in Gray Code

This paper demonstrates how channel coding can improve the robustness of spatial image watermarks against signal distortion caused by lossy data compression such as the JPEG scheme by taking advantage of the properties of Gray code. Two error-correction coding (ECC) schemes are used here: One scheme, referred to as the vertical ECC (VECC), is to encode information bits in a pixel by error-correction coding where the Gray code is used to improve the performance. The other scheme, referred to as the horizontal ECC (HECC), is to encode information bits in an image plane. In watermarking, HECC generates a codeword representing watermark bits, and each bit of the codeword is encoded by VECC. Simple single-error-correcting block codes are used in VECC and HECC. Several experiments of these schemes were conducted on test images. The result demonstrates that the error-correcting performance of HECC just depends on that of VECC, and accordingly, HECC enhances the capability of VECC. Consequently, HECC with appropriate codes can achieve stronger robustness to JPEG—caused distortions than non-channel-coding watermarking schemes.

光学元件磁流变加工不确定度误差工艺方法

为减少磁流变抛光过程中误差对加工精度的影响,实现光学元件磁流变高精度加工,采用一种不确定度误差工艺方法对加工中的误差进行抑制。通过对磁流变加工过程中的位置误差和去除函数误差进行不确定度分析,在理论分析与实验分析的基础上进行验证实验。由仿真与实验结果可知,加工中面形误差与中频误差均存在3.5 nm的不确定度误差值,通过验证实验,得到了加工后的面形误差RMS值为20 nm,中频误差RMS值为14 nm。结果表明,采用误差不确定度的方法可优化加工工艺流程,减少误差对加工过程的影响,可以达到不确定度下的面形精度。该方法为磁流变高精度确定性加工以及面形误差与中频误差的抑制问题提供了一种解决方案。

基于虚拟误差传感的大尺度空间有源降噪性能研究

针对大尺度空间有源降噪系统误差传声器布放位置受限问题,本文使用虚拟误差传感在降噪目标区域放置多个虚拟误差传声器,将静音区由物理误差传声器点转移至虚拟误差传声器点,扩大降噪目标区域中静音区范围。为了对降噪性能及影响因素进行分析与研究,给出多通道虚拟误差传感的原理和算法,对降噪性能及物理与虚拟误差传声器的数量和布放等因素进行仿真分析,在飞机模型舱内进行实验验证。仿真及实验结果表明:使用虚拟误差传感有利于增大降噪目标区域降噪量及静音区;物理与虚拟误差传声器的布放影响静音区的分布;合理的物理与虚拟误差传声器数量及布放可以扩大静音区使其100%覆盖降噪目标区域,最优数量与初级声场频率特性相关。

闽江流域生态效率时空动态演变及驱动因素研究

以闽江流域为研究对象,基于2011—2020年闽江流域面板数据,从环境影响、资源消耗、经济效益角度构建投入产出指标体系,采用考虑非期望产出超效率SBM模型和面板空间误差模型,揭示闽江流域生态效率时空演化特征及驱动机制。研究结果表明:闽江流域生态效率均值总体呈下降趋势,生态效率未达到有效水平县(市)占全样本的比重增加,生态效率出现极化现象并形成“低低集聚、高高集聚”空间格局;生态效率空间分布变化显著且存在空间自相关现象,低生态效率区域呈增加趋势,较高生态效率区域呈减少趋势,生态效率表现为下游>中游>上游的空间分布特征;人均地区生产总值对区域生态效率为正向驱动效应,科技水平、产业结构、政府宏观调控对区域生态效率为负向驱动效应。为此,在新发展格局下要推进闽江流域上游、中游、下游协同发展,优化配置创新资源,促进人才区域合理布局,提升流域整体生态效率。

Spatial Pattern Evolution and Influencing Factors of Cold Storage in China

Cold storage is the vital infrastructure of cold chain logistics. In this study, we analyzed the spatial pattern evolution characteristics, spatial autocorrelation and influencing factors of cold storage in China by using kernel density estimation(KDE), spatial autocorrelation analysis(SAA), and spatial error model(SEM). Results showed that: 1) the spatial distribution of cold storage in China is unbalanced, and has evolved from ‘one core’ to ‘one core and many spots’, that is, ‘one core’ refers to the Bohai Rim region mainly including Beijing, Tianjin, Hebei, Shandong and Liaoning regions, and ‘many spots’ mainly include the high-density areas such as Shanghai, Fuzhou, Guangzhou, Zhengzhou, Hefei, Wuhan, ürümqi. 2) The distribution of cold storage has significant global spatial autocorrelation and local spatial autocorrelation, and the ‘High-High’ cluster area is the most stable, mainly concentrated in the Bohai Rim;the ‘Low-Low’ cluster area is grouped in the southern China. 3) Economic development level, population density, traffic accessibility, temperature and land price, all affect the location choice of cold storage in varying degrees, while the impact of market demand on it is not explicit.

集聚外部性对我国高新技术产业创新效率的影响

应用静态模型对我国各省份高新技术产业创新效率进行评估,并运用空间误差模型探究马歇尔外部性、雅各布外部性和波特外部性对高新技术产业创新效率的影响,发现我国高新技术产业创新效率存在显著的空间相关性和空间溢出效应。结果表明:马歇尔外部性对高新技术产业创新效率影响为负,说明专业化集聚不利于创新效率的提升,而雅各布外部性和波特外部性的影响为正,说明多样化集聚和企业竞争有助于提高创新效率;东部地区高新技术产业创新效率受益于雅各布外部性,被波特外部性抑制;中部地区高新技术产业创新效率受益于马歇尔外部性、雅各布外部性和波特外部性,而西部地区受益于雅各布外部性和波特外部性;大、中规模人口的省份雅各布和波特外部性促进高新技术产业创新效率的提高。

一种多误差因素影响下的空间误差建模方法

目前,关于机床空间误差建模的研究较少考虑由于机床自重引起刀尖点处的偏移量,导致空间误差模型的预测精度与实际结果存在偏差。为了解决上述问题,文章提出一种综合考虑几何误差和机床自重引起刀尖点处偏移量的空间误差建模方法。首先,基于多体系统理论和齐次坐标变换原理建立机床空间误差模型,其次利用正交实验法选出25组加工点,通过仿真分析得到样本点处机床自重引起的刀尖点处偏移量,并通过拟合建立刀尖点偏移量模型,揭示了刀尖点偏移量随加工位置的变化规律,从而建立了一种综合考虑几何误差和机床自重引起刀尖点处偏移量的空间误差模型,最终以“S”形试件为研究对象,进行仿真分析和实验验证,通过对比预测结果和实验结果发现获得的“S”形试件的轮廓误差变化趋势基本相同,残差值较小且低于测量结果的10%,验证了该方法的正确性。该方法的核心思想适用于各类多轴机床。

数控机床几何误差单轴五次测量与辨识方法

针对数控机床几何误差项的准确测量与辨识问题,提出了一种基于激光干涉仪的机床空间几何误差单轴五次测量与辨识方法。首先,针对X、Y、Z轴分别设置了一条测量线,测量了3条划定线上除滚转误差外的其他15项几何误差,共计15次测量;然后,分析了转角误差对直线度误差以及直线度误差对定位误差的耦合影响,并建立了误差辨识方程组;最后,根据误差辨识方程组,得到了机床21项几何误差;并进行了单轴五次测量法的测量和辨识实验,并将所得结果与空间九线法测量辨识结果进行了对比分析。研究结果表明:单轴五次测量法与空间九线法测量辨识结果的空间误差向量最大偏差为1.93μm,平均偏差为0.58μm,该结果验证了单轴五次测量法是准确和有效的。该方法考虑了实际测量过程中的误差耦合情况,因此相比于空间九线法,该方法减少了测量线数与测量次数,简化了误差项的求解过程;同时,采用单轴运动方式可以有效避免其他轴对当前运动轴误差的影响。

基于EFAST方法的三坐标数控机床几何精度灵敏度分析

机床几何误差是影响机床加工精度的主要因素之一,本文针对机床几何误差建模、几何精度灵敏度分析、筛选关键几何误差等问题进行研究。结合多体系统理论和齐次坐标变换建立三坐标数控机床的几何误差模型,求解机床空间位置误差表达式。使用雷尼绍XL-80激光干涉仪对三坐标数控机床进行几何误差测量试验,将测量结果导入九线法误差辨识模型,辨识三坐标数控机床的21项几何误差。应用Simlab软件中的拓展傅里叶幅值灵敏度检验方法(EFAST)对三坐标数控机床的几何误差进行灵敏度分析,并筛选出影响三坐标数控机床加工精度的关键几何误差。此外,以关键几何误差为基础,建立三坐标数控机床的简化几何误差模型,与三坐标数控机床的几何误差模型进行对比分析。结果表明,该方法可合理经济地提高三坐标数控机床加工精度及几何误差补偿。

high-power laser;off-axis reflective exposure system;pulse compression grating;spatial frequency errors;specifications

The large-aperture pulse compression grating(PCG) is a critical component in generating an ultra-high-intensity, ultra-short-pulse laser;however, the size of the PCG manufactured by transmission holographic exposure is limited to large-scale high-quality materials. The reflective method is a potential way for solving the size limitation, but there is still no successful precedent due to the lack of scientific specifications and advanced processing technology of exposure mirrors. In this paper, an analytical model is developed to clarify the specifications of components, and advanced processing technology is adopted to control the spatial frequency errors. Hereafter, we have successfully fabricated a multilayer dielectric grating of 200 mm × 150 mm by using an off-axis reflective exposure system with Φ300 mm. This demonstration proves that PCGs can be manufactured by using the reflection holographic exposure method and shows the potential for manufacturing the meter-level gratings used in 100 petawatt class high-power lasers.

空间耦合低密度奇偶校验码残差滑窗译码算法

针对空间耦合低密度奇偶校验(SC-LDPC)码滑窗译码(SWD)算法中错误传播导致的高误码率问题,该文提出基于动态残差的滑窗译码(RSWD)算法。通过在窗口内计算边信息更新前后的残差值,动态选择可靠度最低(残差值最大)的边信息优先更新,降低边信息无效更新的频率,提高窗内译码收敛速度。仿真结果表明:相比于传统SWD算法,RSWD算法在窗口中各位置的误比特数明显降低,抑制错误传播效果明显;在高信噪比(SNR)区域或者低迭代次数的情况下,RSWD算法的误码率性能优于SWD算法;此外,将动态残差应用到消息复用(MR)和窗口扩展(WE)两种窗译码算法中,亦能得到类似结论,提升窗译码性能。

数字化对制造业和物流业融合发展的影响研究——基于中介效应模型与空间误差模型的实证分析

制造业与物流业的融合发展是推进物流业降本增效、促进制造业转型升级的必由之路,数字化发展为其提供了重要的资源基础和技术支撑。本文在梳理理论机制的基础上,分别测算两业协调发展水平与数字化发展水平,并利用空间误差模型探索数字化发展对两业融合的影响。结果表明:研究期内两业协调发展水平表现出上升趋势,且存在空间集聚特征。数字化发展显著促进了两者的融合,且该推动效应在我国东部和西部地区更为显著。科技创新是重要中介机制,能够加速融合进程,且存在区域异质性。