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An Additive-Multiplicative Cox-Aalen Subdistribution Hazard Model for Competing Risks Data

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Journal of Systems Science & Complexity 2019年第6期32卷 1727-1746页

作者： LI Wanxing long yonghong Department of Statistics School of Mathematics and Information ScienceShaanxi Normal UniversityXi'an 710119China School of Mathematics Renmin University of ChinaBeijing 100872China

This paper proposes a flexible additive-multiplicative Cox-Aalen hazard model which allows time-varying covariate effects for the subdistribution in a competing risks *** ted estimating equation approaches under an covariates-dependent adjusted weight by fitting the Cox proportional hazard model for the censoring distribution are established for inference on the model parametric and nonparametric *** addition,large number properties are presented and the finite sample behavior of the proposed estimators is evaluated through simulation studies,estimators from the proposed method perform satisfactorily on reduction of the *** authors apply our model to a competing risks data set from a tamoxifen trail for breast cancer study.

关键词： Aalen's additive model competing risks cumulative incidence function estimating equation inverse probability of censoring weight proportional hazard function time-varying effects

Real-Time Mosaic Method of Aerial Video Based on Two-Stage Key Frame Selection Method

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Large Dynamic Covariance Matrix Estimation with an Application to Portfolio Allocation:A Semiparametric Reproducing Kernel Hilbert Space Approach

Open Journal of Applied Sciences（应用科学） 2024年第4期 1008页

作者： Minwen Yuan yonghong long Xin Li

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Journal of Systems Science & Complexity 2022年第4期35卷 1429-1457页

作者： PENG Siyang GUO Shaojun long yonghong School of Mathematics Renmin University of ChinaBeijing100086China Institute of Statistics and Big Data Renmin University of ChinaBeijing100086China

The estimation of high dimensional covariance matrices is an interesting and important research topic for many empirical time series problems such as asset allocation. To solve this dimension dilemma, a factor structure has often been taken into account. This paper proposes a dynamic factor structure whose factor loadings are generated in reproducing kernel Hilbert space(RKHS), to capture the dynamic feature of the covariance matrix. A simulation study is carried out to demonstrate its performance. Four different conditional variance models are considered for checking the robustness of our method and solving the conditional heteroscedasticity in the empirical study. By exploring the performance among eight introduced model candidates and the market baseline, the empirical study from 2001 to 2017 shows that portfolio allocation based on this dynamic factor structure can significantly reduce the variance, i.e., the risk, of portfolio and thus outperform the market baseline and the ones based on the traditional factor model.

关键词： Dynamic structure factor models high dimensional covariance matrices portfolio allocation reproducing kernel Hilbert space

基于容性屏蔽的无线电能传输系统有源磁屏蔽结构优化

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电工电能新技术 2024年第6期43卷 49-59页

作者：龙永红李辉孔彭生李中启任立权湖南工业大学轨道交通学院湖南株洲412007 湖南工业大学电气与信息工程学院湖南株洲412007 湖南大学电气与信息工程学院湖南长沙410082

为了改善无线电能传输系统中的磁场泄漏问题,本文提出了一种基于无源容性屏蔽的强耦合有源磁屏蔽结构。首先,在无源容性屏蔽的无线电能传输系统的基础上,设计了一种强耦合有源磁屏蔽线圈结构。其次,给出了此线圈的工作原理与设计方法,... 详细信息

为了改善无线电能传输系统中的磁场泄漏问题,本文提出了一种基于无源容性屏蔽的强耦合有源磁屏蔽结构。首先,在无源容性屏蔽的无线电能传输系统的基础上,设计了一种强耦合有源磁屏蔽线圈结构。其次,给出了此线圈的工作原理与设计方法,推导了数学模型以及等效电路模型。从理论出发解释了容性屏蔽和有源屏蔽的原理,并对屏蔽效果及传输效率受屏蔽线圈参数变化的影响作了分析。最后,结合得到的线圈参数,在所提线圈结构的基础上,设计出了一套电动汽车无线充电系统,通过理论计算、仿真和实验,对所提线圈结构和方法的有效性进行了验证。结果显示,该线圈结构在维持96%以上传输效率的同时,能够将系统的漏磁减少大约40%,实现了降低泄漏磁场和保持高传输效率的目标。

关键词：电动汽车无线电能传输电磁兼容电磁屏蔽电磁场

Image Stitching Method of Non-Ferrous Smelting Scene Based on SIFT Algorithm and Color Constancy

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Open Journal of Applied Sciences 2023年第11期13卷 2055-2067页

作者： Yunmeng Liu yonghong long College of Railway Transportation Hunan University of Technology Zhuzhou China

In non-ferrous smelting scenes, complex environments, uneven lighting conditions, and inaccurate automatic exposure parameters result in the panoramic image having obvious seams and significant brightness differences in different regions. To address these issues, a novel image stitching method based on Scale-Invariant Feature Transform (SIFT) and color constancy theory was proposed. Initially, the input image was preprocessed followed by feature extraction and matching. Subsequently, color constancy processing based on matching points was performed to acquire an image with consistent brightness to be spliced. This process was complemented by the integration of multi-band fusion to enhance the original fusion procedure. Eventually, a spliced image with seamless blending and even luminosity was generated. The method proposed in this paper can obtain panoramic images that were more suitable for human eyes to observe, and greatly improve the subjective and objective performance of panoramic images. In the non-ferrous smelting scene, the PSNR and SSIM scores were improved by 3.555 dB and 0.16 respectively.

关键词： Feature Extraction Image Enhancement Panoramic

Comparative Experimental Study on Heat Transfer Characteristics of Building Exterior Surface at High and Low Altitudes

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Journal of Thermal Science 2024年第3期33卷 1119-1131页

作者： JIA yonghong GUO Shurui LI Jin GUO Lei CHENG Zhu ZHANG Yin YANG Hanyu long Enshen Institute for Disaster Management and Reconstruction Sichuan UniversityChengdu610065China MOE Key Laboratory of Deep Earth Science and Engineering College of Architecture and EnvironmentSichuan UniversityChengdu610065China

The external surface heat transfer coefficient of building envelope is one of the important parameters necessary for building energy saving design,but the basic data in high-altitude area are ***,the authors propose a modified measurement method based on the heat balance of a model building,and use the same model building to measure its external surface heat transfer coefficient under outdoor conditions in Chengdu city,China at an altitude of 520 m and Daocheng city at an altitude of 3750 m *** results show that the total heat transfer coefficient(h_(t))of building surface in high-altitude area is reduced by 34.48%.The influence of outdoor wind speed on the convective heat transfer coefficient(h_(c))in high-altitude area is not as significant as that in low-altitude *** fitting relation between convection heat transfer coefficient and outdoor wind speed is also *** the same heating power,the average temperature rise of indoor and outdoor air at highaltitude is 41.9%higher than that at low altitude,and the average temperature rise of inner wall is 25.8%higher than that at low *** shows that high-altitude area can create a more comfortable indoor thermal environment than low-altitude area under the same energy consumption *** is not appropriate to use the heat transfer characteristics of the exterior surface of buildings in low-altitude area for building energy saving design and related heating equipment selection and system terminal matching design in high-altitude area.

关键词： altitude heat transfer characteristics convective heat transfer coefficient(h_(c)) radiative heat transfer coefficient(h_(r)) external building envelope

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碳基负极材料储钾应用及机制研究进展

稀有金属 2022年第11期46卷 1493-1505页

作者：黄曌龙永红张明湖南工业大学轨道交通学院湖南株洲412007 湖南大学微纳光电器件及应用教育部重点实验室湖南长沙410082

因钾资源储量丰富,价格低廉,且具有类似于锂的物化特性,钾离子电池(KIBs)的推广应用可解决当前锂离子电池供不应求的问题。比较钠离子而言,钾离子可在商业化石墨负极中可逆嵌脱,这对于钾离子电池的产业化发展具有重大意义。然而钾离子... 详细信息

因钾资源储量丰富,价格低廉,且具有类似于锂的物化特性,钾离子电池(KIBs)的推广应用可解决当前锂离子电池供不应求的问题。比较钠离子而言,钾离子可在商业化石墨负极中可逆嵌脱,这对于钾离子电池的产业化发展具有重大意义。然而钾离子因尺寸较大,嵌脱行为缓慢,引起的体积膨胀剧烈,成为电极材料面临的共性问题。近年来,为寻找具有良好嵌钾能力的材料,多种类型的电极体系被开发出来,其中碳基材料因制备简单、廉价环保、稳定性好的特点,被视为最具储钾前景的关键材料。本文系统概述了几种代表性碳基负极材料(如石墨、石墨烯、硬碳、软碳)在KIBs中的研究现状,阐述了各自存在的优势与不足;重点探讨了碳基材料的储钾机制,分析了由钾离子插层、吸附、填充行为组成的3种储钾机制及对电化学性能的影响,并指出在电极表面发生的离子吸附和填充方式呈现出电容效应,更适合于高性能的可逆储钾。最后,对KIBs的下一步研究方向和应用前景进行展望。

关键词：碳基材料钾离子电池(KIBs) 负极储钾机制