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基于Bayes推断的交流接触器剩余电寿命预测 被引量:1
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作者 李奎 马典良 +2 位作者 赵成晨 胡博凯 王浩然 《仪器仪表学报》 EI CAS CSCD 北大核心 2024年第1期34-45,共12页
针对交流接触器可靠性开展研究,首先分析交流接触器的电弧侵蚀机理,建立了计及电弧电压及电弧重燃影响的电弧侵蚀模型,根据该模型仿真得到的交流接触器性能退化特征参量变化过程与交流接触器的实际退化规律一致。分析不同工况下性能退... 针对交流接触器可靠性开展研究,首先分析交流接触器的电弧侵蚀机理,建立了计及电弧电压及电弧重燃影响的电弧侵蚀模型,根据该模型仿真得到的交流接触器性能退化特征参量变化过程与交流接触器的实际退化规律一致。分析不同工况下性能退化数据特征,提出了不同工况下先验信息的等效折算方法,解决了不同工况下的先验信息利用问题。建立了基于Bayes推断的交流接触器剩余电寿命预测模型,提高了剩余电寿命预测精度,实现了利用不同工况下性能退化数据对交流接触器进行剩余电寿命预测。在AC-4、AC-3两种工况下进行了交流接触器电寿命仿真分析及实验分析,相对误差均小于5.5%,验证了方法的准确性。 展开更多
关键词 交流接触器 电弧电压 电弧重燃 bayES推断 剩余电寿命
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基于Bayes时空模型分析HIV/AIDS晚发现的时空分布特征及其影响因素
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作者 邵莉 陈继军 +3 位作者 张宇琦 许静 栗果 高文龙 《中山大学学报(医学科学版)》 CAS CSCD 北大核心 2024年第2期243-252,共10页
【目的】旨在分析兰州市HIV/AIDS晚发现的时空聚集性特征及相关影响因素,明确兰州市HIV/AIDS晚发现高风险地区和时间趋势,为兰州市因地制宜地制定HIV/AIDS防治策略措施提供参考依据。【方法】选择兰州市2011-2018年间新报告的成年HIV/A... 【目的】旨在分析兰州市HIV/AIDS晚发现的时空聚集性特征及相关影响因素,明确兰州市HIV/AIDS晚发现高风险地区和时间趋势,为兰州市因地制宜地制定HIV/AIDS防治策略措施提供参考依据。【方法】选择兰州市2011-2018年间新报告的成年HIV/AIDS病例作为研究对象,研究中所需的数据资料来自兰州市疾病预防控制中心和兰州市统计年鉴。采用Bayes时空模型分析HIV/AIDS晚发现相对风险(RR)的时空分布特征及其影响因素。【结果】2011-2018年间兰州市新报告的HIV/AIDS病例共计1984例,其中HIV/AIDS晚发现者有982例(49.5%),平均年龄为39.67岁,男性占90.9%。老年人和女性HIV/AIDS病例中晚发现的比例更高;城关区(51.1%)、安宁区(50.3%)和榆中县(51.9%)具有高于平均水平的HIV/AIDS晚发现比例;2011-2018年间兰州市总体的晚发现比例呈波动上升趋势。Bayes时空模型分析结果显示,兰州市HIV/AIDS晚发现风险在2011-2015年间波动变化,而在2015年后迅速上升,其RR(95%CI)从1.01(0.84,1.23)上升到1.11(0.77,1.97);红古区和三个县的晚发现风险变化趋势与兰州市的总体变化趋势相似,而城关区和七里河区的晚发现风险呈下降趋势;晚发现相对风险大于1的区县包括:永登县(RR=1.07,95%CI:0.55,1.96)、西固区(RR=1.04,95%CI:0.67,1.49)、城关区(RR=2.41,95%CI:0.85,6.16)和七里河区(RR=2.03,95%CI:1.10,3.27)。冷热点分析结果显示城关区和七里河区为热点区。影响因素分析结果显示,随着人均GDP(RR=0.65,95%CI:0.35,0.90)和HIV/AIDS病例中的男性比例(RR=0.53,95%CI:0.19,0.92)的增高,HIV/AIDS晚发现的相对风险越低;而人口密度(RR=1.35,95%CI:1.01,1.81)越大,晚发现风险越高。【结论】兰州市的HIV/AIDS晚发现风险呈上升趋势,并且存在明显的地区差异特征;人均GDP、HIV/AIDS中男性比例和人口密度是HIV/AIDS晚发现的影响因素。因此,对于晚发现风险高和存在相关风险因素的区县,应重视并制定有针对性的HIV筛查和防治服务,降低HIV/AIDS晚发现比例和风险。 展开更多
关键词 艾滋病 人类免疫缺陷病毒 晚发现 bayes时空模型 分布特征
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黄土抗剪强度参数均值与方差的Bayes估计及其应用
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作者 李萍 董鸾花 +3 位作者 赵枝艳 李金明 沈伟 李同录 《建筑科学与工程学报》 CAS 北大核心 2024年第2期163-172,共10页
为解决黄土强度参数估计问题,从工程勘察项目中共收集统计了3384组Q1、Q2、Q3黄土强度参数黏聚力c、内摩擦角φ值的测试数据,不考虑二者的相关性,将参数均值和方差都作为随机变量,建立起黄土强度参数c、φ的正态-逆伽马先验分布。基于Ba... 为解决黄土强度参数估计问题,从工程勘察项目中共收集统计了3384组Q1、Q2、Q3黄土强度参数黏聚力c、内摩擦角φ值的测试数据,不考虑二者的相关性,将参数均值和方差都作为随机变量,建立起黄土强度参数c、φ的正态-逆伽马先验分布。基于Bayes理论,利用共轭先验法推导了参数后验分布和后验概率密度函数的期望值求解公式,确定了估计的误差。以陕西泾阳黄土边坡为例,利用所建立的先验分布和边坡土层测试强度指标,求取参数的后验分布,进一步估计了边坡失效概率的概率分布和稳定系数均值的概率分布。结果表明:在95%的置信度下,按稳定系数评价,边坡均处于基本稳定状态,且稳定系数置信区间小;按失效概率评价,边坡接近稳定状态,但失效概率的置信区间较大,黄土强度参数的方差控制着边坡失效概率的置信区间,将方差作为随机变量,考虑方差变异性,能更科学地评估黄土工程的可靠度。 展开更多
关键词 黄土 边坡 bayes理论 先验分布 正态-逆伽马分布
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Ⅱ型双删失样本下逆Topp-Leone分布的Bayes估计
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作者 习长新 刘华 张玲 《荆楚理工学院学报》 2024年第4期1-9,共9页
在Ⅱ型双删失样本下,研究了逆Topp-Leone分布参数的极大似然估计,证明了极大似然估计的存在性和唯一性;基于未知参数的先验分布为Gamma分布和Jeffrey分布,分别在三种不同损失函数下,得到逆Topp-Leone分布未知参数的Bayes估计。根据后验... 在Ⅱ型双删失样本下,研究了逆Topp-Leone分布参数的极大似然估计,证明了极大似然估计的存在性和唯一性;基于未知参数的先验分布为Gamma分布和Jeffrey分布,分别在三种不同损失函数下,得到逆Topp-Leone分布未知参数的Bayes估计。根据后验密度函数得到预测密度,进而得到未来观测值在三种损失函数下的预测估计值。为了比较在不同损失下Bayes估计的优劣,采用数值模拟方法计算了各种估计的均值及均方误差,结果表明在Linex损失下未知参数的Bayes估计量更接近真值,均方误差最小。 展开更多
关键词 Ⅱ型双删失 逆Topp-Leone分布 bayES估计 预测
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一类Lindley模型参数的经验Bayes检验收敛速度的改进
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作者 黄金超 《吉首大学学报(自然科学版)》 CAS 2024年第3期13-18,共6页
利用递归核估计和单调性,构造了Lindley模型参数的经验Bayes检验函数,并在适当的条件下,证明了收敛速度的阶可任意接近O(n^(-1)).
关键词 Lindley分布族 递归核估计 bayes检验 经验bayES检验 收敛速度
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Effects of an artificial reef system on demersal nekton assemblages in Xiangshan Bay, China 被引量:9
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作者 姜亚洲 林楠 +3 位作者 袁兴伟 焦海峰 申屠基康 李圣法 《Chinese Journal of Oceanology and Limnology》 SCIE CAS CSCD 2016年第1期59-68,共10页
In 2012,an artificial reef system was deployed in Xiangshan Bay,China,to enhance its fishery resources. To determine the effect of the artificial reef system on the demersal nekton assemblages,a beforeafter-control-im... In 2012,an artificial reef system was deployed in Xiangshan Bay,China,to enhance its fishery resources. To determine the effect of the artificial reef system on the demersal nekton assemblages,a beforeafter-control-impact study design was applied. Comparisons of assemblages from impact and control habitats revealed that the assemblage in the impact area had a gradual response to reef deployment. The assemblages in the impact and control areas changed in different ways after reef deployment. During the study period,total biomass,species richness and average body weight in the control area remained relatively stable,whereas there were significant increases in these indicators in the impact area. Responses to the reefs differed among nekton species,inducing assemblage succession in the reefs post-deployment. Sparus macrocephalus and Cynoglossus abbreviat us benefited most from reef deployment. Conversely,smallsized shrimp Palaemon gravieri showed a progressive decrease in biomass following reef deployment. Overall,the artificial reef system diversified the demersal nekton assemblage,enhanced the total biomass,and increased the proportion of large-sized species. 展开更多
关键词 artificial reefs nekton assemblage before-after-control-impact xiangshan bay
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Spatio-temporal distribution of net-collected phytoplankton community and its response to marine exploitation in Xiangshan Bay 被引量:7
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作者 江志兵 朱旭宇 +3 位作者 高瑜 陈全震 曾江宁 朱根海 《Chinese Journal of Oceanology and Limnology》 SCIE CAS CSCD 2013年第4期762-773,共12页
To explore the spatial-temporal distribution of the phytoplankton community and evaluate the combined effects of marine resource exploitation, net-collected phytoplankton and physical-chemical parameters were investig... To explore the spatial-temporal distribution of the phytoplankton community and evaluate the combined effects of marine resource exploitation, net-collected phytoplankton and physical-chemical parameters were investigated in the Xiangshan Bay during the four seasons of 2010. A total of eight phyla, 97 genera, and 310 species were found, including 232 diatom species, 45 dinoflageUate species and 33 other taxa. The phytoplankton abundances presented a significant (P〈0.001) seasonal difference with the average of 60.66x104 cells/m3. Diatoms (mainly consisting of Coscinodiscus jonesianus, Cerataulina pelagica, Skeletonema costatum, and genus Chaetoceros) dominated the phytoplankton assemblage in all seasons. We found great spatio-temporal variation in community composition based on the multidimensional scaling and similarity analysis. Canonical correspondence analysis show that temperature, nutrition, illumination, and salinity were the main variables associated with microalgal assemblage. Compared with the previous studies, an increase in phytoplankton abundance and change in the dominant species coincided with increased exploitation activities in this bay (e.g. operation of coastal power plants, intensive mariculture, tidal fiat reclamation, and industrial and agricultural development). The present findings suggest that the government should exercise caution when deciding upon developmental patterns in the sea-related economy. 展开更多
关键词 EUTROPHICATION PHYTOPLANKTON thermal discharge xiangshan bay
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Research on changes of coastal land use intensity in bay area during past 30 years——A case study of Xiangshan Bay 被引量:4
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作者 FENG Bai-xiang LI Jia-lin +1 位作者 HE Gai-li HUANG Ri-peng 《Marine Science Bulletin》 CAS 2018年第2期28-43,共16页
Taking the coastal zone of Xiangshan Bay as a study area,based on the information of four TM images of1985,1995,2005,and2015,this study divided the land use types into8categories.Then,through calculating4kinds of inde... Taking the coastal zone of Xiangshan Bay as a study area,based on the information of four TM images of1985,1995,2005,and2015,this study divided the land use types into8categories.Then,through calculating4kinds of index models:land-use dynamic index,conversion matrix,land use structure information entropy,and comprehensive index of land development and utilization intensity,the speed,structure,degree,and the spatial-temporal changes in the land development and utilization of Xiangshan Bay coastal zone from1985to2015are researched and analyzed.Results showed that:from1985to2015,the expansion speed of aquaculture land and salt pan of Xiangshan Bay coastal zone was the fastest,the highest dynamic degree could up to11.97%,construction land expansion rate of the second,with significant increase in the area.Intertidal zone reduced by a maximum speed,and the area of farmland decreased obviously.In that30years,the main land type change direction of Xiangshan Bay coastal zone was the farmland turn into construction land,followed by forest turn into farmland.Information entropy increased by period,the land use structure homogeneity constantly strengthened and regional development became gradually mature.The change rate of land use intensity in each period was greater than zero,and the intensity of land development and utilization in Xiangshan Bay coastal zone was enhanced continuously. 展开更多
关键词 land use development intensity spatial-temporal changes coastal zone of xiangshan bay
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A numerical study on the effect of tidal flat's slope on tidal dynamics in the Xiangshan Bay, China 被引量:3
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作者 LI Li YE Taoyan +1 位作者 HE Zhiguo XIA Yuezhang 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2018年第9期29-40,共12页
The Xiangshan Bay is a semi-enclosed and narrow bay, which is characterized by large scale tidal flats and has been historically utilized through coastal construction and aquaculture engineering. The hydrodynamic mode... The Xiangshan Bay is a semi-enclosed and narrow bay, which is characterized by large scale tidal flats and has been historically utilized through coastal construction and aquaculture engineering. The hydrodynamic model using the Finite Volume Coastal Ocean Model(FVCOM) was constructed to examine the changes of tidal dynamics due to the variation of tidal flat slopes. According to the model results, a decreased slope of a tidal flat would amplify the M2 tidal amplitude and delay the M2 tidal phase in the inner harbor, due to an increased tidal prism, and vice versa. The amplitude of the main shallow-water tide M4 would be amplified/dampened in the entire bay due to the changed bottom friction, if the tidal flat's slope were reduced/increased at the Tie inlet. The phase was advanced. The change of a tidal flat's slope at the Tie inlet had greater impacts on tidal amplitude,phase and duration asymmetry, than that at the Xihu inlet. The impact of changes of the tidal flat slope at the Xihu inlet was small and was constrained locally. Changes in the tidal flats' slopes at the Tie and Xihu inlets changed the tidal duration asymmetry, residual current and tidal energy via modulating tides. The ebb dominance decreased when the tidal flat's slope at the Tie inlet was changed. Decreased/increased ebb dominance occurred when the tidal flat's slope was reduced/increased at the Xihu inlet. The residual current and tidal energy density was amplified/dampened and more/less tidal energy was dissipated, with reduced/increased slope at both of the inlets. The findings in this study are instructive to coastal engineering and estuarine management. 展开更多
关键词 tidal flat's slope tidal dynamics tidal asymmetry tidal energy xiangshan bay
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The benthic diatom community of Xiangshan Bay 被引量:1
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作者 WU Rui GAO Yahui +2 位作者 LAN Dongzhao LAN Binbin FANG Qi 《Marine Science Bulletin》 CAS 2020年第1期43-53,共11页
The samples collected from the surface sediments in Xiangshan Bay,Zhejiang province in May and November 2005 were analyzed under a light microscope.The species composition,abundance,community structure and diversity w... The samples collected from the surface sediments in Xiangshan Bay,Zhejiang province in May and November 2005 were analyzed under a light microscope.The species composition,abundance,community structure and diversity were investigated.A total of 179 taxa belonging to 46 genera of diatom were identified.The result showed that the ecotypes of diatom were mostly eurytopic species,followed by warm water species and temperate species.The most dominant species were Cyclotella stylorum and Coscinodiscus jonesianus.The seasonal variation of diatom abundance was remarkable.The cell abundance of diatoms was higher in spring(2.974×10^3 cells/g)than that in autumn(0.071×10^3 cells/g).The number of species varies with change of season,demonstrating the adaptability of diatoms to the temperature of water.The species diversity of benthic diatom was lower in autumn than that in spring. 展开更多
关键词 xiangshan bay AQUICULTURE benthic diatom community characteristic
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Standing stock of phytoplankton and primary productivity in Penaeus orientalis larval multiplication releasing area of the Xiangshan Bay 被引量:1
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作者 Liu Zilin Cai Yuming +1 位作者 Shi Junxiang Ning Xiuren (1. Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China) 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2000年第1期109-118,共10页
The standing stock of phytoplankton (phy. ) and primary productivity (pp) in the Xiangshan Bay were observed in 1992. The results showed higher biological parameters in the bay. The average chlorophyll a (chl a) con... The standing stock of phytoplankton (phy. ) and primary productivity (pp) in the Xiangshan Bay were observed in 1992. The results showed higher biological parameters in the bay. The average chlorophyll a (chl a) concentration was (3. 50 5. 93 ) mg/m3 and the primary productivity (444. 5 871. 0) mg/(m2 d). The distribution of chl a and productivity showed distinct spatial and temporal patterns in the bay. The continent influence was Obvious at the top of the bay, lower seawater exchange and higher stability led to higher standing stock of phytoplankton and productivity. At the bay mouth, seawater exchanged continuously with adjacent waters by rapid currents, resulting in fast and unstable exchange and lower standing stock of phytoplankton and primary productivity. The seasonal characters of those parameters were pronounced, in the sequence of spring, summer, autumn and winter. The results of size--fractionated showed that the average contribution of the nano--and picoplankton (< 20pm) to total chl a and productivity were 75 % and 87%, respectively, indicating their importance in phytoplankton community biomass and productivity of the Xiangshan Bay. 展开更多
关键词 Standing stock PHYTOPLANKTON chl a primary productivity size-fractionated xiangshan
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A Numerical Study of Tidal Asymmetry: Preferable Asymmetry of Nonlinear Mechanisms in Xiangshan Bay, East China Sea
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作者 XU Peng MAO Xinyan +1 位作者 JIANG Wensheng ZHOU Liangming 《Journal of Ocean University of China》 SCIE CAS 2014年第5期733-741,共9页
In-situ measurements in Xiangshan Bay, the East China Sea, show that the duration of the rising tide is shorter than that of the falling tide around the bay mouth, while it becomes much longer in the inner bay. A fini... In-situ measurements in Xiangshan Bay, the East China Sea, show that the duration of the rising tide is shorter than that of the falling tide around the bay mouth, while it becomes much longer in the inner bay. A finite volume coastal ocean model(FVCOM) with an unstructured mesh was applied to simulate the asymmetric tidal field of Xiangshan Bay. The model reproduced the observed tidal elevations and currents successfully. Several numerical experiments were conducted to clarify the roles of primary mechanisms underlying the asymmetric tidal field. According to the model results, the time-varying channel depth and nonlinear advection prefer shorter duration of the rising tide in Xiangshan Bay, while the time-varying bay width favors longer duration of the rising tide. The overtides generated by these two opposite types of nonlinear mechanisms are out of phase, resulting in smaller M4 amplitude than the sumfold of each individual contribution. Although the bottom friction as a nonlinear mechanism contributes little to the generation of overtide M4, it is regarded as a mechanism that could cause a shorter duration of the rising tide, for it can slow down the M2 phase speed much more than it slows down the M4 phase speed. The time-varying depth, nonlinear advection and bottom friction are dominating factors around the bay mouth, while the time-varying width dominates in the inner bay, causing the tidal elevation asymmetry to be inverted along the bay. 展开更多
关键词 FVCOM tidal asymmetry xiangshan bay nonlinear mechanisms
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Tide-induced Lagrangian residual velocity and dynamic analysis based on field observations in the inner Xiangshan Bay,China
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作者 Xiaoxuan Sheng Qi Quan +2 位作者 Jinzhen Yu Xinyan Mao Wensheng Jiang 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2022年第10期32-40,共9页
In the Xiangshan Bay at the east coast of China,coastal marine pollution is conspicuous and severe in recent years.As transport of the pollutants is closely related to the coastal circulation,there is a great practica... In the Xiangshan Bay at the east coast of China,coastal marine pollution is conspicuous and severe in recent years.As transport of the pollutants is closely related to the coastal circulation,there is a great practical significance to investigate the circulation in this area.In this work,the surface pattern and vertical profiles of Lagrangian residual velocity(LRV)were studied based on field observation data from the inner Xiangshan Bay.By tracking GPS-GPRS drifters’trajectories,the surface LRV pattern is going out in the central deep trough and flowing inwards near the shoreside.Combined with data from two mooring stations,vertical profiles of LRV is flowing out at surface and flowing in at the bottom,consistent with the gravitational circulation induced by baroclinic effects at the estuary.However,according to the diagnostic analysis,the main mechanism driving the residual current is barotropic rather than baroclinic.The LRV equation is controlled by the tidally-averaged barotropic pressure gradient force,tidal body force and tidally-averaged turbulent stress,while the tidallyaveraged baroclinic pressure gradient force is one order of magnitude less than other forces.Additionally,the tidally mean eddy viscosity coefficient which is used in the expression of tidally-averaged turbulent stress might be not adequate and requires further studies. 展开更多
关键词 Lagrangian residual velocity GPS-GPRS drifters mooring observation xiangshan bay
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A Comprehensive Lagrangian Transport Study in A Long-Narrow Bay,Xiangshan Bay,China
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作者 HAN Song-lin LIANG Shu-xiu +1 位作者 WANG Xing-gang SUN Zhao-chen 《China Ocean Engineering》 SCIE EI CSCD 2020年第4期581-588,共8页
Study on the transport and mixing in coastal waters is of great concern to the ocean resources exploitation and ecological system protection.Lagrangian methods are direct and effective of researching mass transport.Tw... Study on the transport and mixing in coastal waters is of great concern to the ocean resources exploitation and ecological system protection.Lagrangian methods are direct and effective of researching mass transport.Two Lagrangian tools were adopted and combined to describe water transport in a long-narrow bay,Xiangshan Bay,China.Based on the fields of tidal velocity simulated from the 3-D hydrodynamic model,Lagrangian Coherent Structures(LCSs)and synoptic Lagrangian maps(SLMs)were calculated in the study area.Through comparison of the results,the features and relation of the two tools were discussed.The results show that the LCSs act as the separatrix of the water regions with different transport characteristics and can identify the water areas with different transport time scales.The comprehensive application of the Lagrangian tools is helpful to obtain more insight into the water transport process. 展开更多
关键词 transport and mixing Lagrangian coherent structures synoptic Lagrangian maps xiangshan bay
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核主泵机械密封可靠性Bayes分析的适应性
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作者 高灯 孙见君 张玉言 《润滑与密封》 CAS CSCD 北大核心 2024年第2期155-161,共7页
机械密封的可靠性对核主泵的安全稳定运行具有重要影响。为解决无失效数据情形下核主泵机械密封的可靠度评估问题,分析大亚湾核主泵机械密封的运行数据,确定其可靠度分布,建立结合Bayes理论的可靠性分析模型,利用Monte Carlo法从确定的... 机械密封的可靠性对核主泵的安全稳定运行具有重要影响。为解决无失效数据情形下核主泵机械密封的可靠度评估问题,分析大亚湾核主泵机械密封的运行数据,确定其可靠度分布,建立结合Bayes理论的可靠性分析模型,利用Monte Carlo法从确定的可靠度分布中仿真出无失效数据,探讨无失效数据场合下,先验分布为Beta分布时,分组数c的取值对E-Bayes估计与多层Bayes估计精度的影响。研究表明:分组数c<8时,优先选择多层Bayes估计;c>8,优先选择E-Bayes估计,c=8时,2种方法的平均相对误差均达到较低水平且多层Bayes估计更低一些。研究成果对无失效数据场合下基于Bayes理论的核主泵机械密封可靠性分析具有指导意义。 展开更多
关键词 无失效数据 bayes理论 核主泵 机械密封 可靠性
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偏态分布截断参数的经验Bayes检验
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作者 刘蕊 谭燕 吴刘仓 《高校应用数学学报(A辑)》 北大核心 2024年第1期13-27,共15页
偏态分布是对称分布的一种推广,在实际生活中应用广泛,其中截断参数对界定偏态分布的边界具有重要意义.文中基于经验Bayes检验方法,研究了偏态分布截断参数的假设检验问题.考虑普通Bayes检验中先验密度的未知性和不确定性,利用递归核估... 偏态分布是对称分布的一种推广,在实际生活中应用广泛,其中截断参数对界定偏态分布的边界具有重要意义.文中基于经验Bayes检验方法,研究了偏态分布截断参数的假设检验问题.考虑普通Bayes检验中先验密度的未知性和不确定性,利用递归核估计的密度函数代替未知的先验密度函数.定义检验的加权线性损失函数,从而更好地刻画了决策风险.在给定条件下证明了所提出检验函数的渐近最优性,同时给出确定的收敛速度.最后通过实例验证了文中的理论结果. 展开更多
关键词 经验bayES检验 偏态分布 递归核估计 渐近最优性 收敛速度
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Detecting and assessing Spartina invasion in coastal region of China: A case study in the Xiangshan Bay
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作者 ZHU Changming ZHANG Xin QI Jiaguo 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2016年第4期35-43,共9页
Spartina alterniflora is one of exotic plants along the coastal region in China. It was introduced as an important engineering approach to ecological restoration in the later 1970 s. However, owing to its good adaptab... Spartina alterniflora is one of exotic plants along the coastal region in China. It was introduced as an important engineering approach to ecological restoration in the later 1970 s. However, owing to its good adaptability and strong reproductive capacity, the introduced species is explosively spreading along the coastal region quickly and resulting in a significant impact on the health and safety of coastal wetland ecosystems. It is imperative to quantify the spatial extent and the rate of S. alterniflora sprawl in order to assess its ecological damages and economic impacts. Remote sensing techniques have been used to address these challenges but large unsuccessful due to mixed spectral properties. In this study, a hybrid method was proposed for S. alterniflora detection using medium resolution remote sensing images by integrating both spatial and spectral features of S. alterniflora. The hybrid method consists of two phases:(1) delineation of intertidal zone as the potential area of S. alterniflora distribution and(2) extraction of S. alterniflora fraction distribution with a mixture pixel analysis. The proposed method was tested at the Xiangshan Bay on the east coastal region of Zhejiang Province, China, and mapped the spatial extent of S. alterniflora with Landsat datasets in the 2003, 2009 and 2014. The results showed that, the S. alterniflora has grown exponentially over past 10 years. In 2003, the total area of S. alterniflora was about 590 hm2, but quickly reached to 1 745 hm2 in 2009, and 5 715 hm2 in 2014. With a rate of approximately 10-folds growth within a decade, the invasive species almost occupied all muddy beaches to become the most dominant coastal salt vegetation in this region. It is believed that the strong biological reproductive capacity was the primary reason for such quick spread and at the same time human reclamation activities were also believed to have facilitated the environmental conditions for S. alterniflora sprawl. 展开更多
关键词 Spartina alterniflora invasive species remote sensing xiangshan bay
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加权p、q 对称损失函数下Burr分布参数的Bayes估计
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作者 于雪松 徐宝 《广西师范大学学报(自然科学版)》 CAS 北大核心 2024年第6期186-193,共8页
在加权p、q对称损失函数下,利用Bayes参数估计方法研究Burr分布参数Bayes估计的形式和估计的性质,得到参数Bayes估计的一般形式以及在无信息先验分布和共轭先验分布下的精确形式,并证明所得估计具有可容许性和最小最大性,进一步得到参... 在加权p、q对称损失函数下,利用Bayes参数估计方法研究Burr分布参数Bayes估计的形式和估计的性质,得到参数Bayes估计的一般形式以及在无信息先验分布和共轭先验分布下的精确形式,并证明所得估计具有可容许性和最小最大性,进一步得到参数的多层Bayes估计。最后用R软件结合MCMC算法对所得估计进行数值模拟,结果表明在共轭先验分布下的Bayes估计比无信息先验分布下的Bayes估计精度更高。 展开更多
关键词 BURR分布 损失函数 bayES估计 可容许性 MCMC算法
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不同环境下含零失效数据的系统可靠性Bayes评估方法
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作者 唐庆 郝威巍 +1 位作者 孔祥睿 孙永全 《黑龙江大学自然科学学报》 CAS 2024年第1期28-37,共10页
针对船舶装备电子系统在研制阶段经历多种试验,且试验环境应力存在明显差异性及试验过程存在零失效的情况,基于电子系统失效率,提出了零失效情况下环境因子置信区间确定方法,并提出零失效情况下各阶段试验时间及故障数据的折合方式。构... 针对船舶装备电子系统在研制阶段经历多种试验,且试验环境应力存在明显差异性及试验过程存在零失效的情况,基于电子系统失效率,提出了零失效情况下环境因子置信区间确定方法,并提出零失效情况下各阶段试验时间及故障数据的折合方式。构建了电子系统失效率的先验分布模型,利用Bayes方法融合试验信息给出失效率的点估计及置信限,方便后续的可靠性评估。并以某船舶电子系统为例,验证了可靠性评估方法的有效性,为船舶典型装备电子系统可靠性评估提供了参考。 展开更多
关键词 电子系统 零失效 环境因子 bayES可靠性评估
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无失效威布尔情形下基于双修正多层Bayes的可靠性评估
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作者 龙足腾 郑波 +1 位作者 甯洋 罗金超 《工程设计学报》 CSCD 北大核心 2024年第1期59-66,共8页
利用配分布曲线法构建无失效数据的可靠性评估模型时,往往采用E-Bayes或多层Bayes来估计失效概率,但因其估计能力有限,整体可靠度点估计精度不高。针对威布尔分布数据提出了一种新的双修正多层Bayes方法,用于改善失效概率估计,并完成可... 利用配分布曲线法构建无失效数据的可靠性评估模型时,往往采用E-Bayes或多层Bayes来估计失效概率,但因其估计能力有限,整体可靠度点估计精度不高。针对威布尔分布数据提出了一种新的双修正多层Bayes方法,用于改善失效概率估计,并完成可靠度点估计。在多层Bayes的基础上,通过修正失效概率上下限值来减小失效概率估计误差,然后结合加权最小二乘法和威布尔分布可靠度函数确定参数估计值和可靠度曲线,从而得到可靠度点估计。利用Monte-Carlo仿真试验,发现新方法能将参数估计相对误差控制在10%以下,并且得到的可靠度值更加趋近真值。通过实例分析发现,在超参数c取不同值的情况下,采用新方法得到的可靠度都更加接近工程实际。新方法适用性分析表明,形状参数β是影响估计精度的关键因素,且在β>2.2时新方法具有明显的优势及良好的稳健性。研究结果可为其他寿命分布无失效数据的可靠性评估提供参考。 展开更多
关键词 无失效威布尔 失效概率估计 双修正多层bayes 可靠度估计 适用性分析
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