Formation mechanism of a smooth, defectfree surface of fused silica optics using rapid CO2 laser polishing

Surface defects introduced by conventional mechanical processing methods can induce irreversible damage and reduce the service life of optics applied in high-power lasers.Compared to mechanical processing,laser polishing with moving beam spot is a noncontact processing method,which is able to form a defect-free surface.This work aims to explore the mechanism of forming a smooth,defect-free fused silica surface by high-power density laser polishing with coupled multiple beams.The underlying mechanisms of laser polishing was revealed by numerical simulations and the theoretical results were verified by experiments.The simulated polishing depth and machined surface morphology were in close agreement with the experimental results.To obtain the optimized polishing quality,the effects of laser polishing parameters(e.g.overlap rate,pulse width and polishing times)on the polishing quality were experimentally investigated.It was found that the processing efficiency of fused silica materials by carbon dioxide(CO2)laser polishing could reach 8.68 mm2 s−1,and the surface roughness(Ra)was better than 25 nm.Besides,the cracks on pristine fused silica surfaces introduced by initial grinding process were completely removed by laser polishing to achieve a defect-free surface.The maximum laser polishing rate can reach 3.88μm s−1,much higher than that of the traditional mechanical polishing methods.The rapid CO2 laser polishing can effectively achieve smooth,defect-free surface,which is of great significance to improve the surface quality of fused silica optics applied in high-power laser facilities.

A-Smooth Regularization for Ill-Posed Equations with Perturbed Operators and Noisy Data

This paper concerns the A smooth regularization method for linear ill posed equations in the presence of perturbed operators and noisy data. The semi and full a posteriori Morozov discrepancy principles for choosing the regularization parameter are proposed, which lead to satisfactory results.

On the rate of convergence of two generalized Bernstein type operators

In this paper,we introduce the Bézier variant of two new families of generalized Bernstein type operators.We establish a direct approximation by means of the Ditzian-Totik modulus of smoothness and a global approximation theorem in terms of second order modulus of continuity.By means of construction of suitable functions and the method of Bojanic and Cheng,we give the rate of convergence for absolutely continuous functions having a derivative equivalent to a bounded variation function.

Segment-based traffic smoothing algorithm for VBR video stream

Transmission of variable bit rate (VBR) video, because of the burstiness of VBR video traffic, has high fluctuation in bandwidth requirement. Traffic smoothing algorithm is very efficient in reducing burstiness of the VBR video stream by trans- mitting data in a series of fixed rates. We propose in this paper a novel segment-based bandwidth allocation algorithm which dynamically adjusts the segmentation boundary and changes the transmission rate at the latest possible point so that the video segment will be extended as long as possible and the number of rate changes can be as small as possible while keeping the peak rate low. Simulation results showed that our approach has small bandwidth requirement, high bandwidth utilization and low computation cost.

Functional Time Series Models to Estimate Future Age-Specific Breast Cancer Incidence Rates for Women in Karachi, Pakistan

Background： Breast cancer is the most common female cancer in Pakistan. The incidence of breast cancer in Pakistan is about 2.5 times higher than that in the neighboring countries India and Iran. In Karachi, the most populated city of Pakistan, the age-standardized rate of breast cancer was 69.1 per 100,000 women during 1998-2002, which is the highest recorded rate in Asia. The carcinoma of breast in Pakistan is an enormous public health concern. In this study, we examined the recent trends of breast cancer incidence rates among the women in Karachi. Methods： We obtained the secondary data of breast cancer incidence from various hospitals. They included Jinnah Hospital, KIRAN （Karachi Institute of Radiotherapy and Nuclear Medicine）, and Civil hospital, where the data were available for the years 2004-2011. A total of 5331 new cases of female breast cancer were registered during this period. We analyzed the data in 5-year age groups 15-19, 20-24, 25-29, 30-34, 35-39, 40-44, 45-49, 50-54, 55-59, 60-64, 65-69, 70-74, 75＋. Nonparametric smoothing were used to obtained age-specific incidence curves, and then the curves are decomposed using principal components analysis to fit FTS （functional time series） model. We then used exponential smoothing statspace models to estimate the forecasts of incidence curve and construct prediction intervals. Results： The breast cancer incidence rates in Karachi increased with age for all available years. The rates increased monotonically and are relatively sharp with the age from 15 years to 50 years and then they show variability after the age of 50 years. 10-year forecasts for the female breast cancer incidence rates in Karachi show that the future rates are expected to remain stable for the age-groups 15-50 years, but they will increase for the females of 50-years and over. Hence in future, the newly diagnosed breast cancer cases in the older women in Karachi are expected to increase. Conclusion： Prediction of age related changes in breast cancer incidence rates will provide useful information for controlling the overall burden of cancer in Pakistan and also serve as a resource for health planning in future research. Moreover, these models will be the most useful for modeling and projecting future trends of other cancers and chronic diseases.

New Rate Allocation Method for MPEG-4 FGS Video Streaming

A new rate allocation method for fine-granular scalability (FGS) coded bitstreams is presented in order to achieve smooth quality reconstruction of frames under channel conditions with a wide range of bandwidth variation and improve the average PSNR of the whole sequence. Based on a quality weighted bit allocation method, a sliding window rate allocation method is proposed for the first time so that the window can slide along the video sequence with a certain sliding step. Experimental results show that, under dynamic bandwidth conditions, the proposed method can simultaneously satisfy the requirements for improving average PSNR of the whole video sequence greatly and reducing the fluctuations between adjacent frames greatly.

Some New Estimators of Integrated Volatility

We develop higher order accurate estimators of integrated volatility in a stochastic volatility models by using kernel smoothing method and using different weights to kernels. The weights have some relationship to moment problem. As the bandwidth of the kernel vanishes, an estimator of the instantaneous stochastic volatility is obtained. We also develop some new estimators based on smoothing splines.

Research progress on the effect of oocyte smooth endoplasmic reticulum clusters on early embryo development and pregnancy outcome

With the clinical development and application of intracytoplasmic sperm injection(ICSI)technology in human assisted reproduction,the influence of oocyte quality on embryo development has been paid more and more attention.So far,there have been many reports on oocyte morphology affecting embryo development.It has been found in some works that the appearance of smooth endoplasmic reticulum clusters(SERC)in oocytes may affect the fertilization and embryo development of oocytes.However,with the increasing reports of SERC-containing oocytes obtained by in vitro fertilization and healthy offspring in recent years,there is still some controversy on whether to continue to use SERC-containing oocytes for the following assisted reproductive therapy in clinical practice.Based on this,this review aims to review the research progress of SERC in oocytes in recent years.

Methods for Estimating Mean Annual Rate of Earthquakes in Moderate and Low Seismicity Regions

Two kinds of methods for determining seismic parameters are presented, that is, the potential seismic source zoning method and grid-spatially smoothing method. The Gaussian smoothing method and the modified Gaussian smoothing method are described in detail, and a comprehensive analysis of the advantages and disadvantages of these methods is made. Then, we take centrai China as the study region, and use the Gaussian smoothing method and potential seismic source zoning method to build seismic models to calculate the mean annual seismic rate. Seismic hazard is calculated using the probabilistic seismic hazard analysis method to construct the ground motion acceleration zoning maps. The differences between the maps and these models are discussed and the causes are investigated. The results show that the spatial smoothing method is suitable for estimating the seismic hazard over the moderate and low seismicity regions or the hazard caused by background seismicity; while the potential seismic source zoning method is suitable for estimating the seismic hazard in well-defined seismotectonics. Combining the spatial smoothing method and the potential seismic source zoning method with an integrated account of the seismicity and known seismotectonics is a feasible approach to estimate the seismic hazard in moderate and low seismicity regions.

考虑产水量变化的气井井筒结垢堵塞预测

为提高气井解堵措施的针对性,综合考虑气井井筒无机物结垢的热力学和动力学影响,特别是考虑气井产水量变化与垢在井筒内壁的黏附系数,建立了气井井筒结垢堵塞预测模型,并应用于靖边气田。结果表明:基于平滑指数法预测了气井日产水量,预测时间越长,累积产水量的误差越小。加权系数α越小,预测结果越精准,模型中α取0.2;通过现场生产资料拟合,垢在井筒内壁的黏附系数取0.001时,能够取得较为满意的预测结果;现场应用结果表明该模型预测的结垢堵塞物组成和堵塞程度与现场相符,对气井井筒除垢解堵措施具有指导意义。

沙特NEOM隧道项目光面爆破高效施工方法研究与应用

传统的隧道光面爆破装药结构复杂,需投入较多人力提前加工药串,装药速度较慢,人工和辅助材料成本较高,且药卷固定不牢易使药卷集中,造成光面爆破效果不佳。结合沙特NEOM隧道支洞项目所在地的施工习惯和其他外部施工条件、隧道岩石性质、钻孔条件和爆破器材种类等因素,设计出一种40g/m高能导爆索和2号岩石乳化炸药组合式的光面爆破装药结构,通过改变装药结构和装药方法,省去提前加工药串步骤,节省了人力和辅助材料投入,相较于传统的光面爆破装药结构简单、耗时短、可操作性较强、对爆破作业人员的技术水平要求也较低。经爆破测试表明,采用此施工方法光面爆破效果较好,残孔率达到88%~92%,能有效提高光面爆破施工效率,改善光面爆破效果,降低隧道爆破开挖施工成本。

基于纵横比自适应的相关滤波跟踪算法

由于跟踪过程目标不规则形变的影响,采用固定纵横比的尺度模型无法精确地估计目标的尺度.为解决该问题,本文提出基于纵横比自适应的相关滤波跟踪算法.基于fDSST(fast Discriminative Scale Space Tracking)算法,训练学习纵横比模型,更新目标的纵横比,获取更精确的目标尺度.在此基础上,本文设计了平滑修正方案以及学习率自适应机制,可以有效地缓解因目标出现遮挡导致的模型漂移问题.在OTB100、VOT2016和VOT2018数据集上与其他跟踪算法进行对比实验,结果表明本文算法改善了基准算法的性能,特别是在OTB100上的总体准确率和成功率比fDSST提高了9.6%和6.2%.

融合协同效应的自适应图卷积网络推荐算法

基于图神经网络的协同过滤算法在许多推荐场景中取得了良好的表现,但是现有的图神经网络推荐模型在推荐过程中忽略了节点间协同效应与节点-层级的重要性融合表达以及堆叠多层网络容易存在过平滑问题。为解决上述问题,文中提出一种新的融合协同效应的自适应图卷积网络推荐算法。首先,构建用户-项目二部图并计算节点间交互率;其次,根据节点局部结构自适应决定节点-层级的融合表达权重;然后,利用第l层与第l+1层嵌入向量的相似度来缓解图卷积网络的过平滑问题;最后,使用协同效应融合自适应图卷积网络学习潜在的特征并通过内积作为结果进行推荐。在五个真实数据集上的实验结果表明,所提模型相比基线模型,在召回率和归一化折损累计增益两个评价指标上有明显提高。

基于GA-BPNN混合智能模型的钻速预测

石油勘探和开发领域中,准确预测机械钻速对于提高钻井效率和降低工程风险至关重要。准确的机械钻速预测为制定钻井方案、评估钻井风险提供重要依据,但对于复杂的非线性的钻井系统,传统的钻速方程和机器学习方法无法全面考虑影响机械钻速的因素。本文基于一种遗传算法优化的反向传播神经网络的机械钻速预测模型,以中国南海某油田历史钻井数据为基础,通过SG平滑处理,归一化处理和Pearson、Spearman和Kendall相关系数综合分析进行特征参数选择的数据预处理,与BP、RBF、MEA-BP神经网络模型以及ELM、RF、SVM、KNN等传统机器学习方法进行比较验证。实验结果表明,GA-BP的R 2为0.967,预测值与实测值具有良好的一致性,比标准BP神经网络预测R 2精确提高了17.64%,也较其他模型具有更准确的预测结果。这种混合智能预测模型能够准确预警和预防钻井事故,为指导油田钻井施工参数提供有效数据,从而提高钻井施工的经济效益。

一种GNSS/加速度计数据融合方法探讨

针对目前桥梁施工合拢过程中的关键技术挂篮安全监测的方法主要利用全站仪和水准仪等传统设备,人员成本高,效率低,且难以满足实时监测等问题,提出一种GNSS/加速度计数据融合方法:分析全球卫星导航系统(GNSS)由于其具有无须通视、全天候以及能够直接测量点的三维坐标等优点,已广泛应用于变形监测领域,但受多路径、采样率等因素影响,对高频振动不敏感,而加速度计具有高采样率、性能稳定等优点,但其对低频信息不敏感;结合2种传感器的优势,利用基于Rauch-Tung-Striebel(RTS)平滑的多速率抗差卡尔曼滤波方法对GNSS和加速度数据进行融合处理。实验结果表明,该方法可有效提高GNSS挂篮振动监测的采样率和精度。

基于纹理信息的图像自适应分块压缩感知算法

针对传统分块压缩感知算法中对各图像块分配相同采样率,限制图像重构质量的问题,本文提出一种基于纹理信息的采样率自适应分块压缩感知算法。在观测端将图像一维灰度熵和标准差作为纹理信息量的衡量标准,使用K-means++算法将图像块按照纹理信息的相似性分为3类;结合边缘信息为3类图像块分配自适应采样率,并进行采样率二次分配;在重构端为缓解重构图像产生的块效应,采用分层分块结构结合改进的平滑投影Landweber算法进行重构。实验结果表明:在不同的采样率下,本算法重构图像在客观重构质量和主观视觉效果上均有一定提升,重构图像的块效应也得到缓解。

MFCDD优化三次样条平滑算法在继电器数据插值中的应用

继电器参数众多,并且对各参数的测量方式和测量间隔不同,释放电压等参数相较于时间参数等实时测量参数,数据量较少,在进行相关分析时会造成结果精度较差的情况。提出一种形态波动一致性偏移距离(MFCDD)优化的平滑指标改进三次样条插值算法。引入平滑指标改进,对数据序列相关点的方差贡献率及单点平滑度进行分析,确定数据序列的平滑点及波动点;采用三次指数平滑对三次样条算法进行改进,确定改进后的插值表达式;引入形态波动一致性偏移距离对插值间隔进行确定,完成数据扩充。采用继电器吸合电压参数和释放电压参数对上述方法进行验证,结果表明上述方法对数据扩充具有较好的准确性。

人民币对三种货币汇率波动特征与区域影响分析——基于MSAR模型及Bai-Perron检验

由于汇率时间序列经常呈现出波动的频繁性、非线性与易受国内外因素影响的特点,因此本文利用MSAR模型及Bai-Perron检验分析了人民币对美元、欧元、卢布的汇率波动所处的不同状态及结构性断点来捕捉汇率波动的结构性显著变化。党的二十大报告指出有序推进人民币国际化,人民币国际化先从区域化开始,人民币影响力的体现是人民币汇率波动对其他国家汇率波动有显著的作用,这种作用相对主要国际货币如美元、日元、欧元、英镑等相当或影响更大,因此选取与我国贸易往来密切的周边东南亚及亚太等八个国家的货币汇率波动作为分析对象,同样运用MSAR模型进行实证检验。结果表明,人民币汇率对以上选取货币汇率具有两种状态的明显转换特点,且人民币汇率波动在升值和贬值两种状态下对其他货币的升值和贬值起到一定的作用,这种作用与国际货币相当,人民币在周边区域表现出一定的影响力。

VBR流式视频的最短路径率平滑传输算法

预存储的变比特率 (VBR)压缩的视频网上流式传输 ,提供实时视频服务 .这种VBR视频呈现的突发性比特率变化特性使带宽预留和接纳控制等网络传输技术复杂化 .一个行之有效的解决办法是在传输前对这种VBR视频在满足一定限制条件下进行比特率无损平滑 .基于平面规划中的最短路径原理 ,针对存储的VBR压缩视频 ,文章提出了最短路径率平滑传输算法 ,并建立了一些相关概念 .算法的结果被证明能同时满足多项优化指标 :极小的峰值比特率、极大的谷值比特率及O(K)的时间复杂性 ,实验结果也显示算法是有效、可行的 .

基于小波包分解的混合储能技术在平抑风电场功率波动中的应用

在充分分析风电功率幅频特性的基础上,提出基于小波包分解的混合储能技术平抑风电场输出功率波动的方法。采用小波包分解理论对风电场输出功率信号进行多尺度分解,得到反映并网功率信号的低频信号和接入储能系统的高频信号;根据不同类型储能系统的特点,将高频信号再次进行划分,分别选择与其频率范围适应的电池和超级电容器储能设备,建立了基于混合储能系统的风电场输出功率平滑控制模型;与单类型电池储能系统功率平滑效果进行了对比。仿真实例表明:该方法能够有效地抑制风电场输出功率的波动,提高储能电池的使用寿命,具有一定的工程应用价值。