Based on the quality and analysis of the medium carbon product whose grade was 81%-82%, the emphasis of the study was placed on the orthogonal experiments of roughing flotation reagent and single factors, such as abra...Based on the quality and analysis of the medium carbon product whose grade was 81%-82%, the emphasis of the study was placed on the orthogonal experiments of roughing flotation reagent and single factors, such as abrasive grain, pulp concentration and the rotating speed of flotation machine. The result with improvement in the grade of concentrate to 95% through the routine floatation method was achieved.展开更多
The state-of-art Computational Fluid Dynamics （CFD） codes FLUENT is applied in a fine-scale simulation of the wind field over a complex terrain. Several numerical tests are performed to validate the capability of FL...The state-of-art Computational Fluid Dynamics （CFD） codes FLUENT is applied in a fine-scale simulation of the wind field over a complex terrain. Several numerical tests are performed to validate the capability of FLUENT on describing the wind field details over a complex terrain. The results of the numerical tests show that FLUENT can simulate the wind field over extremely complex terrain, which cannot be simulated by mesoscale models. The reason why FLUENT can cope with extremely complex terrain, which can not be coped with by mesoscale models, relies on some particular techniques adopted by FLUENT, such as computer-aided design （CAD） technique, unstructured grid technique and finite volume method. Compared with mesoscale models, FLUENT can describe terrain in much more accurate details and can provide wind simulation results with higher resolution and more accuracy.展开更多
It is shown that the fine structure constant at Planck times tends to one as well as those of the weak and strong interactions. This results by constraining them at the Planck force. That seems to provide interesting ...It is shown that the fine structure constant at Planck times tends to one as well as those of the weak and strong interactions. This results by constraining them at the Planck force. That seems to provide interesting new results which confirm that at the beginning of space time (Planck scale) all fundamental forces converge to the same unit value.展开更多
在细粒度图像检索领域,现有研究成果主要集中于采用深层网络实现判别特征提取与精准定位,忽略了浅层特征信息的重要性,且无法消除背景中的复杂噪声干扰,限制了检索性能的提升。有鉴于此,提出了一种基于多层次特征提取的细粒度图像哈希...在细粒度图像检索领域,现有研究成果主要集中于采用深层网络实现判别特征提取与精准定位,忽略了浅层特征信息的重要性,且无法消除背景中的复杂噪声干扰,限制了检索性能的提升。有鉴于此,提出了一种基于多层次特征提取的细粒度图像哈希检索方法(Fine-grained Deep Hashing image retrieval method based on Multi-level Feature Extraction, FDH-MFE)。该方法主要关注不同层次间特征的关联性,并增强了局部特征的提取能力。首先,提出了一个特征提取模块,旨在从网络的不同阶段提取细粒度特征,并通过图神经网络揭示其潜在的长距离依赖关系,为后续阶段提供更全面和精细的特征表示。其次,设计了一种代理损失算法,使得哈希码分布更加均匀,从而提升细粒度特征的区分能力。最后,通过设计背景抑制算法并结合三元组损失,增强了模型拟合全局分布的能力,使得所提出的方法在细粒度图像检索任务中表现出色。实验结果表明:该方法在4个公开数据集上的平均检索精度相较于次先进方法分别提高了15.03%、10.94%、9.98%和9.78%。展开更多
To understand nutrient cycling in soils, soil processes and microorganisms need be better characterized. To determine whether specific trophic groups of fungi are associated with soil enzyme activity, we used soil imp...To understand nutrient cycling in soils, soil processes and microorganisms need be better characterized. To determine whether specific trophic groups of fungi are associated with soil enzyme activity, we used soil imprinting to guide mm-scale sampling from microsites with high and low phosphatase activities in birch/Douglas-fir stands. Study 1 involved sampling one root window per site at 12 sites of different ages(stands);study 2 was conducted at one of the stem-exclusion stands, at which 5 root windows had been installed. Total fungal and ectomycorrhizal(EM) fungal terminal-restriction fragment length polymorphism(TRFLP)fingerprints differed between high-and low-phosphatase activity microsites at 8 of 12 root windows across 12 sites. Where differences were detected, fewer EM fungi were detected in high-than low-phosphatase activity microsites. Using 5 root windows at one site,next-generation sequencing detected similar fungal communities across microsites, but the ratio of saprotrophic to EM fungal reads was higher in high-phosphatase activity microsites in the two windows that had low EM fungal richness. In windows with differences in fungal communities, both studies indicated that EM fungi were less successful than saprotrophic fungi in colonizing fine-scale,organic matter-rich microsites. Fine-scale sampling linked with in situ detection of enzyme activity revealed relationships between soil fungal communities and phosphatase activity that could not be observed at the scales employed by conventional approaches, thereby contributing to the understanding of fine-scale phosphorus cycling in forest soils.展开更多
This paper presents the development of a coarse-fine dual precision positioning stage to achieve long travel range and high accuracy.The fine stage is arranged in series with a coarse stage.The key in the fine stage d...This paper presents the development of a coarse-fine dual precision positioning stage to achieve long travel range and high accuracy.The fine stage is arranged in series with a coarse stage.The key in the fine stage design is the choice of a toggle mechanism for a tight mechanical loop with high stiffness and compactness.We designed the toggle mechanism for reduction of the displacement to suppress signal noises.The performance of the coarse and fine stages was verified with an optical encoder and capacitive sensor,respectively.The measurement results show that the dual mechanism has a travel range of 1 mm and resolution of 30 nm.展开更多
Anthropogenic activities are triggering planetary-scale transformations at an unprecedented rate,leading to profound impacts on biodiversity and ecosystem stability(Williams et al.2020;Ellis et al.2021).Human encroach...Anthropogenic activities are triggering planetary-scale transformations at an unprecedented rate,leading to profound impacts on biodiversity and ecosystem stability(Williams et al.2020;Ellis et al.2021).Human encroachment and the reduction of natural habitats are projected to imperil approximately 1700 terrestrial vertebrate species by 2070(Powers and Jetz 2019).These changes not only directly impact the persistence of individual species but also reshape community structures and ecosystem functions by altering intra-and interspecific interactions(Sévêque et al.2020;O’Connor et al.2024).展开更多
植被分布信息是开展自然资源保护、生态系统健康评价的重要数据基础。山区地形起伏大、植被类型结构复杂,传统植被遥感分类基于二维影像进行制图,无法反映植被垂直结构和三维空间分布特征。为探索实景三维模型在植被精细分类与制图上的...植被分布信息是开展自然资源保护、生态系统健康评价的重要数据基础。山区地形起伏大、植被类型结构复杂,传统植被遥感分类基于二维影像进行制图,无法反映植被垂直结构和三维空间分布特征。为探索实景三维模型在植被精细分类与制图上的应用潜力,该文提出了一种融合光学影像与激光雷达(light detecting and ranging, LiDAR)数据的实景三维模型山地植被制图方法。选取广东内伶仃岛为研究区,利用无人机航测获取的实景三维模型、多光谱与LiDAR点云构建多源数据集,开展多源数据配准和特征提取;进一步采用LightGBM算法实现植被精细分类并评估多源数据特征的分类性能;最后,通过二维制图向三维模型的映射获得植被语义三维模型。结果表明,实景三维模型可以有效区分植被类型,其与多光谱、LiDAR数据的特征融合能更全面地描述山区地形与植被结构特性,二维分类总精度比仅使用单一数据提升4.28%~11.29%。基于实景三维模型的植被三维制图总精度达到92.06%,Kappa系数为0.89,能够真实直观地反映山地植被的立体层次分布规律,提高植被精细信息提取的准确性。研究验证了实景三维模型与多源数据的融合在自然资源监测中的巨大潜力,为区域植被精细化和立体化信息提取提供新的思路和方法。展开更多
文摘Based on the quality and analysis of the medium carbon product whose grade was 81%-82%, the emphasis of the study was placed on the orthogonal experiments of roughing flotation reagent and single factors, such as abrasive grain, pulp concentration and the rotating speed of flotation machine. The result with improvement in the grade of concentrate to 95% through the routine floatation method was achieved.
基金supported by the National Natural Science Foundation of China(40805004, 40705039 and 90715031)the "Mini-projecton detailed survey and evaluation of wind energy resources"supported by National Climate Center of Chinese Meteoro-logical Administration (CWERA2010002)
文摘The state-of-art Computational Fluid Dynamics （CFD） codes FLUENT is applied in a fine-scale simulation of the wind field over a complex terrain. Several numerical tests are performed to validate the capability of FLUENT on describing the wind field details over a complex terrain. The results of the numerical tests show that FLUENT can simulate the wind field over extremely complex terrain, which cannot be simulated by mesoscale models. The reason why FLUENT can cope with extremely complex terrain, which can not be coped with by mesoscale models, relies on some particular techniques adopted by FLUENT, such as computer-aided design （CAD） technique, unstructured grid technique and finite volume method. Compared with mesoscale models, FLUENT can describe terrain in much more accurate details and can provide wind simulation results with higher resolution and more accuracy.
文摘It is shown that the fine structure constant at Planck times tends to one as well as those of the weak and strong interactions. This results by constraining them at the Planck force. That seems to provide interesting new results which confirm that at the beginning of space time (Planck scale) all fundamental forces converge to the same unit value.
文摘在细粒度图像检索领域,现有研究成果主要集中于采用深层网络实现判别特征提取与精准定位,忽略了浅层特征信息的重要性,且无法消除背景中的复杂噪声干扰,限制了检索性能的提升。有鉴于此,提出了一种基于多层次特征提取的细粒度图像哈希检索方法(Fine-grained Deep Hashing image retrieval method based on Multi-level Feature Extraction, FDH-MFE)。该方法主要关注不同层次间特征的关联性,并增强了局部特征的提取能力。首先,提出了一个特征提取模块,旨在从网络的不同阶段提取细粒度特征,并通过图神经网络揭示其潜在的长距离依赖关系,为后续阶段提供更全面和精细的特征表示。其次,设计了一种代理损失算法,使得哈希码分布更加均匀,从而提升细粒度特征的区分能力。最后,通过设计背景抑制算法并结合三元组损失,增强了模型拟合全局分布的能力,使得所提出的方法在细粒度图像检索任务中表现出色。实验结果表明:该方法在4个公开数据集上的平均检索精度相较于次先进方法分别提高了15.03%、10.94%、9.98%和9.78%。
基金supported by the Natural Sciences and Engineering Research Council of Canada (RGPIN170627-03, RGPIN170627-08 to M. D. Jones)the British Columbia Forest Innovation Investment—Forest Science Program (Y051064 to Suzanne Simard and M. D. Jones, Y081186 to M. D. Jones and S. J. Grayston)
文摘To understand nutrient cycling in soils, soil processes and microorganisms need be better characterized. To determine whether specific trophic groups of fungi are associated with soil enzyme activity, we used soil imprinting to guide mm-scale sampling from microsites with high and low phosphatase activities in birch/Douglas-fir stands. Study 1 involved sampling one root window per site at 12 sites of different ages(stands);study 2 was conducted at one of the stem-exclusion stands, at which 5 root windows had been installed. Total fungal and ectomycorrhizal(EM) fungal terminal-restriction fragment length polymorphism(TRFLP)fingerprints differed between high-and low-phosphatase activity microsites at 8 of 12 root windows across 12 sites. Where differences were detected, fewer EM fungi were detected in high-than low-phosphatase activity microsites. Using 5 root windows at one site,next-generation sequencing detected similar fungal communities across microsites, but the ratio of saprotrophic to EM fungal reads was higher in high-phosphatase activity microsites in the two windows that had low EM fungal richness. In windows with differences in fungal communities, both studies indicated that EM fungi were less successful than saprotrophic fungi in colonizing fine-scale,organic matter-rich microsites. Fine-scale sampling linked with in situ detection of enzyme activity revealed relationships between soil fungal communities and phosphatase activity that could not be observed at the scales employed by conventional approaches, thereby contributing to the understanding of fine-scale phosphorus cycling in forest soils.
基金supported by the National Science Council (No.NSC-96-2628-E002-199)
文摘This paper presents the development of a coarse-fine dual precision positioning stage to achieve long travel range and high accuracy.The fine stage is arranged in series with a coarse stage.The key in the fine stage design is the choice of a toggle mechanism for a tight mechanical loop with high stiffness and compactness.We designed the toggle mechanism for reduction of the displacement to suppress signal noises.The performance of the coarse and fine stages was verified with an optical encoder and capacitive sensor,respectively.The measurement results show that the dual mechanism has a travel range of 1 mm and resolution of 30 nm.
基金supported by the National Natural Science Foundation of China(32271737 and 32071544)the Interdisciplinary Innovation Team of the Chinese Academy of Sciences(CAS)“Light of West China”Program(xbzg-zdsys-202207).
文摘Anthropogenic activities are triggering planetary-scale transformations at an unprecedented rate,leading to profound impacts on biodiversity and ecosystem stability(Williams et al.2020;Ellis et al.2021).Human encroachment and the reduction of natural habitats are projected to imperil approximately 1700 terrestrial vertebrate species by 2070(Powers and Jetz 2019).These changes not only directly impact the persistence of individual species but also reshape community structures and ecosystem functions by altering intra-and interspecific interactions(Sévêque et al.2020;O’Connor et al.2024).
文摘植被分布信息是开展自然资源保护、生态系统健康评价的重要数据基础。山区地形起伏大、植被类型结构复杂,传统植被遥感分类基于二维影像进行制图,无法反映植被垂直结构和三维空间分布特征。为探索实景三维模型在植被精细分类与制图上的应用潜力,该文提出了一种融合光学影像与激光雷达(light detecting and ranging, LiDAR)数据的实景三维模型山地植被制图方法。选取广东内伶仃岛为研究区,利用无人机航测获取的实景三维模型、多光谱与LiDAR点云构建多源数据集,开展多源数据配准和特征提取;进一步采用LightGBM算法实现植被精细分类并评估多源数据特征的分类性能;最后,通过二维制图向三维模型的映射获得植被语义三维模型。结果表明,实景三维模型可以有效区分植被类型,其与多光谱、LiDAR数据的特征融合能更全面地描述山区地形与植被结构特性,二维分类总精度比仅使用单一数据提升4.28%~11.29%。基于实景三维模型的植被三维制图总精度达到92.06%,Kappa系数为0.89,能够真实直观地反映山地植被的立体层次分布规律,提高植被精细信息提取的准确性。研究验证了实景三维模型与多源数据的融合在自然资源监测中的巨大潜力,为区域植被精细化和立体化信息提取提供新的思路和方法。
