通过灌溉对作物根区土壤水盐环境进行适时适度的调控是促进新疆绿洲农业可持续健康发展的重要举措,其中最为关键的一环当属灌溉制度尤其是灌水定额的优化。为了提高灌水控盐效率,该研究以新疆沙湾市膜下滴灌盐碱棉田为研究对象,以当地...通过灌溉对作物根区土壤水盐环境进行适时适度的调控是促进新疆绿洲农业可持续健康发展的重要举措,其中最为关键的一环当属灌溉制度尤其是灌水定额的优化。为了提高灌水控盐效率,该研究以新疆沙湾市膜下滴灌盐碱棉田为研究对象,以当地传统灌溉制度为对照,在基于作物水分亏缺指数(plant water deficit index,PWDI)评估并实施智能灌溉的基础上开展了2 a(2021与2022)田间灌水控盐试验,通过设置不同的盐分淋洗系数(2021年:1.0与2.0;2022年:1.0、1.4、1.8、2.2与2.6)探讨灌水定额对土壤水盐运移与棉花生长以及水分吸收利用的影响。结果表明,在固定PWDI阈值(评估值超过阈值时开启灌水)的情况下,在一定范围内随着盐分淋洗系数的增大,灌水定额增加,灌水周期延长,灌水总量增大,更多盐分被被淋洗到根区下部甚至根区以下,从而改善根域水盐环境,减轻水盐胁迫,促进棉花生长并增产,但灌溉水利用效率呈缓慢下降趋势。然而,当盐分淋洗系数(灌水定额)增大到一定程度时,长期优越的根域水盐环境导致棉花徒长,即营养生长旺盛而生殖生长迟滞,灌水周期缩短,灌水总量急剧上升,产量不再增加反而有下降趋势,灌溉水利用效率显著降低。综合考虑盐分淋洗、棉花生长与产量以及水分利用效率,当试验区PWDI阈值取为0.5时建议对应的盐分淋洗系数取为2.2。该研究可为新疆盐碱棉田高效生产以及绿洲农业可持续健康发展提供理论依据与技术支撑。展开更多
为实现桥梁裂缝的快速、准确定位,考虑光照变化、污渍阴影等干扰因素的影响,提出一种结合桥梁检测机和改进单阶段目标检测(you only look once version 3,YOLOv3)算法的桥梁裂缝检测方法。首先,在预处理阶段,采用改进自适应Mask匀光算...为实现桥梁裂缝的快速、准确定位,考虑光照变化、污渍阴影等干扰因素的影响,提出一种结合桥梁检测机和改进单阶段目标检测(you only look once version 3,YOLOv3)算法的桥梁裂缝检测方法。首先,在预处理阶段,采用改进自适应Mask匀光算法对数据集进行处理,矫正阴影和光照不均等问题,提高算法环境适应能力;其次,在目标检测阶段,针对桥梁裂缝的特点,对数据集使用k-means++算法聚类先验框以适应裂缝的不同尺寸,采用广义交并比对YOLOv3损失函数进行改进以提高定位精度;最后,采用迁移学习对YOLOv3进行训练。实验结果表明,在迭代140个epoch后,检测速度可达到31帧/s,平均精度(average precision,AP)达到94.88%,相比于采用原始数据集的原始YOLOv3网络AP值提高了13.16%,能够满足实时性和高精度的检测要求。展开更多
Our knowledge of the oceanic lithosphere largely comes from analogy with ophiolite complexes and the direct scientific drilling of the present-day oceanic crust(e.g.,Christensen and Salisbury,1975,1989;Smith and Vine,...Our knowledge of the oceanic lithosphere largely comes from analogy with ophiolite complexes and the direct scientific drilling of the present-day oceanic crust(e.g.,Christensen and Salisbury,1975,1989;Smith and Vine,1989;Dilek and Furnes,2011,2014).In this study,we summarized previous experimental results on seismic properties of oceanic lower crust and upper mantle according to different tectonic settings.The results are used to highlight the compositional heterogeneity and the nature of the oceanic Moho.Observation in different ophiolites reveal an ideal oceanic lithosphere profile with ideal petrologic units and seismic units(Dilek and Furnes,2011,2014).The lithospheric mantle beneath ocean basins is composed of tectonized peridotites,which include layered lherzolites and harzburgites and lenses of dunites with chromitites and nearly correspond to the seismic Layer 4.The overlying layered gabbros and mafic sheeted dike complex equal to the seismic Layer 3,as a result of crystallization from a magma chamber.The transitional unit between the former two petrologic units consists of layered ultramafic and mafic rocks,corresponds to the petrological Moho.The seismic Layer 2 and 1 are well defined by pillow lavas and massive flows,and the overlying abyssal sediments,respectively.Compared these results with the refraction seismic profiles,the oceanic crust and upper mantle show different composition and structure.The Pwave velocities of the Layer 3 gabbros varies from 6.7 to 7.0 km s-1 and have low velocity gradients of<0.1 km s-1.Although the gradual increase of P-and S-wave velocities with depth can be attributed to the increasing proportion of mafic minerals from the top to the bottom,prehnite-pumpellyite facies alteration of basalts,greenschist-faces metamorphism to epidote-amphibolite facies metamorphism of gabbros will decrease the velocities of the Layer 2 and Layer 3(Christensen and Salisbury,1975,1989),because the P-wave velocities of chlorite and hornblende are 6.00 and 7.00 km s-1,respectively,lower than those of plagioclase and pyroxene,respectively(Carlson,2004).In addition,local velocity anomalies near the petrologic Moho can be related serpentinization of ultramafic rocks(Salisbury and Christensen,1978;Carlson et al.,2009).In the Layer 4,the characteristic P-wave velocities of the upper mantle should fall in the range of 7.8 to 8.2 km s-1.Poisson’s ratios of chrysotile and lizardite,which are stable in oceanic crustal environments according to the phase diagram,is 0.267 and 0.359,respectively,higher than those of olivine and pyroxene(Wang et al.,2013).Serpentinization will significantly decreased velocities and densities of peridotites and is the main reason for the variation of the Moho reflectivity beneath oceans.展开更多
To increase customers'satisfaction and promote product's competitiveness,a customized extended warranty(EW)policy is proposed,where the diversities in both the usage rate and purchase date are considered.The m...To increase customers'satisfaction and promote product's competitiveness,a customized extended warranty(EW)policy is proposed,where the diversities in both the usage rate and purchase date are considered.The marginal approach is applied to describe the product's two-dimensional failure in terms of age and usage,respectively.Moreover,minimal repair is adopted to restore the failure,and the virtual age method is applied to depict the effect of preventive maintenance(PM).On this basis,an optimization model is established to minimize the maintenance cost and warranty cost from the manufacturer's view,and multiple factors are taken into account,including the PM's intensity and its period,and EW's interval,etc.A numerical case study is provided to illustrate the effectiveness of the proposed approach.The results show that by considering the product's usage rate and the purchasing date of EW,the number of failures as well as the cost of maintenance and warranty can be reduced effectively.展开更多
文摘通过灌溉对作物根区土壤水盐环境进行适时适度的调控是促进新疆绿洲农业可持续健康发展的重要举措,其中最为关键的一环当属灌溉制度尤其是灌水定额的优化。为了提高灌水控盐效率,该研究以新疆沙湾市膜下滴灌盐碱棉田为研究对象,以当地传统灌溉制度为对照,在基于作物水分亏缺指数(plant water deficit index,PWDI)评估并实施智能灌溉的基础上开展了2 a(2021与2022)田间灌水控盐试验,通过设置不同的盐分淋洗系数(2021年:1.0与2.0;2022年:1.0、1.4、1.8、2.2与2.6)探讨灌水定额对土壤水盐运移与棉花生长以及水分吸收利用的影响。结果表明,在固定PWDI阈值(评估值超过阈值时开启灌水)的情况下,在一定范围内随着盐分淋洗系数的增大,灌水定额增加,灌水周期延长,灌水总量增大,更多盐分被被淋洗到根区下部甚至根区以下,从而改善根域水盐环境,减轻水盐胁迫,促进棉花生长并增产,但灌溉水利用效率呈缓慢下降趋势。然而,当盐分淋洗系数(灌水定额)增大到一定程度时,长期优越的根域水盐环境导致棉花徒长,即营养生长旺盛而生殖生长迟滞,灌水周期缩短,灌水总量急剧上升,产量不再增加反而有下降趋势,灌溉水利用效率显著降低。综合考虑盐分淋洗、棉花生长与产量以及水分利用效率,当试验区PWDI阈值取为0.5时建议对应的盐分淋洗系数取为2.2。该研究可为新疆盐碱棉田高效生产以及绿洲农业可持续健康发展提供理论依据与技术支撑。
文摘为实现桥梁裂缝的快速、准确定位,考虑光照变化、污渍阴影等干扰因素的影响,提出一种结合桥梁检测机和改进单阶段目标检测(you only look once version 3,YOLOv3)算法的桥梁裂缝检测方法。首先,在预处理阶段,采用改进自适应Mask匀光算法对数据集进行处理,矫正阴影和光照不均等问题,提高算法环境适应能力;其次,在目标检测阶段,针对桥梁裂缝的特点,对数据集使用k-means++算法聚类先验框以适应裂缝的不同尺寸,采用广义交并比对YOLOv3损失函数进行改进以提高定位精度;最后,采用迁移学习对YOLOv3进行训练。实验结果表明,在迭代140个epoch后,检测速度可达到31帧/s,平均精度(average precision,AP)达到94.88%,相比于采用原始数据集的原始YOLOv3网络AP值提高了13.16%,能够满足实时性和高精度的检测要求。
文摘Our knowledge of the oceanic lithosphere largely comes from analogy with ophiolite complexes and the direct scientific drilling of the present-day oceanic crust(e.g.,Christensen and Salisbury,1975,1989;Smith and Vine,1989;Dilek and Furnes,2011,2014).In this study,we summarized previous experimental results on seismic properties of oceanic lower crust and upper mantle according to different tectonic settings.The results are used to highlight the compositional heterogeneity and the nature of the oceanic Moho.Observation in different ophiolites reveal an ideal oceanic lithosphere profile with ideal petrologic units and seismic units(Dilek and Furnes,2011,2014).The lithospheric mantle beneath ocean basins is composed of tectonized peridotites,which include layered lherzolites and harzburgites and lenses of dunites with chromitites and nearly correspond to the seismic Layer 4.The overlying layered gabbros and mafic sheeted dike complex equal to the seismic Layer 3,as a result of crystallization from a magma chamber.The transitional unit between the former two petrologic units consists of layered ultramafic and mafic rocks,corresponds to the petrological Moho.The seismic Layer 2 and 1 are well defined by pillow lavas and massive flows,and the overlying abyssal sediments,respectively.Compared these results with the refraction seismic profiles,the oceanic crust and upper mantle show different composition and structure.The Pwave velocities of the Layer 3 gabbros varies from 6.7 to 7.0 km s-1 and have low velocity gradients of<0.1 km s-1.Although the gradual increase of P-and S-wave velocities with depth can be attributed to the increasing proportion of mafic minerals from the top to the bottom,prehnite-pumpellyite facies alteration of basalts,greenschist-faces metamorphism to epidote-amphibolite facies metamorphism of gabbros will decrease the velocities of the Layer 2 and Layer 3(Christensen and Salisbury,1975,1989),because the P-wave velocities of chlorite and hornblende are 6.00 and 7.00 km s-1,respectively,lower than those of plagioclase and pyroxene,respectively(Carlson,2004).In addition,local velocity anomalies near the petrologic Moho can be related serpentinization of ultramafic rocks(Salisbury and Christensen,1978;Carlson et al.,2009).In the Layer 4,the characteristic P-wave velocities of the upper mantle should fall in the range of 7.8 to 8.2 km s-1.Poisson’s ratios of chrysotile and lizardite,which are stable in oceanic crustal environments according to the phase diagram,is 0.267 and 0.359,respectively,higher than those of olivine and pyroxene(Wang et al.,2013).Serpentinization will significantly decreased velocities and densities of peridotites and is the main reason for the variation of the Moho reflectivity beneath oceans.
基金The National Natural Science Foundation of China(No.71671035)the Project of 2018 Intelligent Manufacturing Comprehensive Standard of Ministry of Industry and Information Technology of Chinathe Open Fund of Jiangsu Wind Power Engineering Technology Center of China(No.ZK19-03-03)。
文摘To increase customers'satisfaction and promote product's competitiveness,a customized extended warranty(EW)policy is proposed,where the diversities in both the usage rate and purchase date are considered.The marginal approach is applied to describe the product's two-dimensional failure in terms of age and usage,respectively.Moreover,minimal repair is adopted to restore the failure,and the virtual age method is applied to depict the effect of preventive maintenance(PM).On this basis,an optimization model is established to minimize the maintenance cost and warranty cost from the manufacturer's view,and multiple factors are taken into account,including the PM's intensity and its period,and EW's interval,etc.A numerical case study is provided to illustrate the effectiveness of the proposed approach.The results show that by considering the product's usage rate and the purchasing date of EW,the number of failures as well as the cost of maintenance and warranty can be reduced effectively.
