Classification of stellar spectra with SVM based on within-class scatter and between-class scatter     

Zhong-bao Liu  Fang-xiao Zhou  Zhen-tao Qin  Xue-gang Luo  Jing Zhang 《Astrophysics and Space Science》2018,363(7):140

Support Vector Machine (SVM) is a popular data mining technique, and it has been widely applied in astronomical tasks, especially in stellar spectra classification. Since SVM doesn’t take the data distribution into consideration, and therefore, its classification efficiencies can’t be greatly improved. Meanwhile, SVM ignores the internal information of the training dataset, such as the within-class structure and between-class structure. In view of this, we propose a new classification algorithm-SVM based on Within-Class Scatter and Between-Class Scatter (WBS-SVM) in this paper. WBS-SVM tries to find an optimal hyperplane to separate two classes. The difference is that it incorporates minimum within-class scatter and maximum between-class scatter in Linear Discriminant Analysis (LDA) into SVM. These two scatters represent the distributions of the training dataset, and the optimization of WBS-SVM ensures the samples in the same class are as close as possible and the samples in different classes are as far as possible. Experiments on the K-, F-, G-type stellar spectra from Sloan Digital Sky Survey (SDSS), Data Release 8 show that our proposed WBS-SVM can greatly improve the classification accuracies.  相似文献   

Extreme Flood Events over the Past 300 Years Inferred from Lake Sedimentary Grain Sizes in the Altay Mountains,Northwestern China     

Jianchao Zhou  Jinglu Wu  Haiao Zeng 《中国地理科学(英文版)》2018,28(5):773-783

Understanding the temporal variations of extreme floods that occur in response to climate change is essential to anticipate the trends in flood magnitude and frequency in the context of global warming. However, long-term records of paleofloods in arid regions are scarce, thus preventing a thorough understanding of such events. In this study, a reconstruction of paleofloods over the past 300 years was conducted through an analysis of grain sizes from the sediments of Kanas Lake in the Altay Mountains of northwestern China. Results showed that grain parameters and frequency distributions can be used to infer possible abrupt environmental events within the lake sedimentary sequence, and two extreme flood events corresponding to ca. 1736–1765 AD and ca. 1890 AD were further identified based on canonical discriminant analysis(CDA) and coarse percentile versus median grain size(C-M) pattern analysis, both of which occurred during warmer and wetter climate conditions by referring to tree-ring records. These two flood events are also evidenced by lake sedimentary records in the Altay and Tianshan mountains. Furthermore, through a comparison with other records, the flood event from ca. 1736–1765 AD in the study region seems to have occurred in both the arid central Asia and the Alps in Europe, and thus may have been associated with changes in the North Atlantic Oscillation(NAO) index.  相似文献   

风和径流量对长江口缺氧影响的数值模拟   总被引：1，自引：1，他引：0  

郑静静  刘桂梅  高姗  李云  李志杰 《海洋学报》2018,40(9):1-17

受自然和人类活动的影响，海洋缺氧现象日益严重，威胁着海洋生态环境，海洋缺氧问题已经引起了人们的广泛关注。本文应用区域海洋模式并耦合生态模式，对东海的生态系统进行了数值模拟和分析研究。与观测数据比较显示，该模型能较好地模拟长江口外生态变量的分布趋势。另外本文通过设置不同敏感性实验，探讨风和径流量对长江口底层缺氧现象的影响，结果分析表明，风和径流量对长江口外缺氧区的形成有显著的影响。径流量变化虽然对长江口外缺氧区的季节变化影响并不显著，但是对缺氧区域面积却存在显著的影响。径流量增加，水体层化增强，表层叶绿素浓度增加，最终导致缺氧区域范围扩展；径流量减小，水体层化减弱，表层叶绿素浓度减小，缺氧区域范围缩小。风向和风速的改变不仅影响长江口外缺氧区的季节变化，还影响缺氧区域面积。  相似文献   

Photosynthetic response of <Emphasis Type="Italic">Scirpus validus</Emphasis> and <Emphasis Type="Italic">Typha orientalis</Emphasis> to elevated temperatures in Dianchi Lake,Southwestern China     

Jun-ping Xu  Mei Sun  Hang Wang  Yun Zhang  Xiao-tang Zhang  Kun Tian 《山地科学学报》2018,15(12):2666-2675

Understanding the effects of simulated warming on photosynthetic performance of aquatic plants may provide strong supports for predicting future dynamics of wetland ecosystems in the context of climate change. The plateau wetlands located in Yunnan province are highly sensitive to climate warming due to their high altitude and cold temperature. Here, we conducted a temperaturecontrolled experiment using two temperature manipulations (ambient temperature as the control and 2°C higher than ambient temperature as the warmed treatment) to determine the photosynthetic characteristics of two lakeside dominant species (Scirpus validus Vahl and Typha orientalis C. Presl.) in Dianchi Lake. Net photosynthetic rate (P_n), stomatal conductance (G_s), intercellular CO₂ concentration (C_i), and transpiration rate of S. validus that grew under warmed treatment were all significantly higher than those under the control. G_s and C_i of T. orientalis showed similar patterns as S. validus did. For the response curves of P_n to photosynthetic active radiation (Pn-PAR) and intercellular CO₂ concentration (P_n-C_i), S. validus had higher P_n values under elevated temperatures than the control, while P_n-PAR and P_n-C_i curves of T. orientalis did not separate clearly under two temperature scenarios. Both S. validus and T. orientalis had higher maximum net photosynthetic rate, light saturation point, dark respiration rate, the maximum rate of RuBP carboxylation (V_cmax), maximum electron transport rate driving RuBP regeneration (J_max), the ratio of V_cmax to J_max, triosephosphate utilization, and 1, 5-bishosphate carboxylase ribulose content under warmed treatment than those under the control. This study provides a preliminary step for predicting the future primary production and vegetation dynamics of plateau wetlands in Yunnan province.  相似文献   

Soil and Vegetation Spectral Coupling Difference (SVSCD) for Minerals Extraction from Hyperion Data in Vegetation Covered Area     

Shengbo Chen  Shuang Huang  Yanli Liu  Chao Zhou 《中国地理科学(英文版)》2018,28(6):957-972

Remote sensing data have been widely applied to extract minerals in geologic exploration, however, in areas covered by vegetation, extracted mineral information has mostly been small targets bearing little information. In this paper, we present a new method for mineral extraction aimed at solving the difficulty of mineral identification in vegetation covered areas. The method selected six sets of spectral difference coupling between soil and plant (SVSCD). These sets have the same vegetation spectra reflectance and a maximum different reflectance of soil and mineral spectra from Hyperion image based on spectral reflectance characteristics of measured spectra. The central wavelengths of the six, selected band pairs were 2314 and 701 nm, 1699 and 721 nm, 1336 and 742 nm, 2203 and 681 nm, 2183 and 671 nm, and 2072 and 548 nm. Each data set’s reflectance was used to calculate the difference value. After band difference calculation, vegetation information was suppressed and mineral abnormal information was enhanced compared to the scatter plot of original band. Six spectral difference couplings, after vegetation inhibition, were arranged in a new data set that requires two components that have the largest eigenvalue difference from principal component analysis (PCA). The spatial geometric structure features of PC1 and PC2 was used to identify altered minerals by spectral feature fitting (SFF). The collecting rocks from the 10 points that were selected in the concentration of mineral extraction were analyzed under a high-resolution microscope to identify metal minerals and nonmetallic minerals. Results indicated that the extracted minerals were well matched with the verified samples, especially with the sample 2, 4, 5 and 8. It demonstrated that the method can effectively detect altered minerals in vegetation covered area in Hyperion image.  相似文献   

Prediction of Blast-Induced Rock Movement During Bench Blasting: Use of Gray Wolf Optimizer and Support Vector Regression     

Yu  Zhi  Shi  Xiuzhi  Zhou  Jian  Chen  Xin  Miao  Xiaohu  Teng  Bing  Ipangelwa  Timo 《Natural Resources Research》2020,29(2):843-865

Natural Resources Research - A large ore loss and dilution can be expected when using a pre-blast ore boundary for shovel guidance because of the movement and re-distribution of ore in the muck...  相似文献   

Post-earthquake economic resilience and recovery efficiency in the border areas of the Tibetan Plateau: A case study of areas affected by the Wenchuan Ms 8.0 Earthquake in Sichuan,China in 2008     

Zhou  Kan  Liu  Baoyin  Fan  Jie 《地理学报(英文版)》2020,30(8):1363-1381

Journal of Geographical Sciences - The border areas of the Tibetan Plateau and the neighboring mountainous areas have a high incidence of earthquakes with a magnitude greater than Ms 5.0, as well...  相似文献   

Fast genetic mapping in barley: case studies of cuticle mutants using RNA-sequencing     

XiaoFeng Li  Chao Li  Qin Zhou  GuoXiong Chen  PengShan Zhao 《寒旱区科学》2020,12(3):180-188

Barley(Hordeum vulgare L.) is one of the earliest domesticated crop species and ranked as the fourth largest cereal production worldwide. Forward genetic studies in barley have greatly advanced plant genetics during the last century; however, most genes are identified by the conventional mapping method. Array genotyping and exome-capture sequencing have also been successfully used to target the causal mutation in barley populations, but these techniques are not widely adopted because of associated costs and partly due to the huge genome size of barley. This review summarizes three mapping cases of barley cuticle mutants in our laboratory with the help of RNA-sequencing. The causal mutations have been successfully identified for two of them and the target genes are located in the pericentromeric regions. Detailed information on the mapping-by-sequencing, mapping-and-sequencing, and RNA-sequencing assisted linkage mapping are presented and some limitations and challenges on the mapping assisted by RNA sequencing are also discussed. The alternative and elegant methods presented in this review may greatly accelerate forward genetics of barley mapping, especially for laboratories without large funding.  相似文献   

滨海城市竖向避难场所选址可靠性评价与若干问题探讨     

张威涛  任利剑  运迎霞 《地理科学》2020,40(11):1899-1908

关注滨海城市竖向避难场所的选址可靠性问题，首先深化确立“竖向避难场所”概念；然后构建竖向避难场所选址可靠性评价模型，综合自然地理要素和建成环境要素，从与灾害直接作用相关的选址暴露性、与应急交通相关的选址敏感性、与应急服务相关的选址适应性3个维度展开，搭建3级评价指标体系；再以天津滨海新区为例、聚焦滨海城市潮洪灾害和人口安全矛盾的集核——临港城区展开实证研究，借助ArcGIS分类与可视化发现：高低可靠性选址之间具有明显的空间分异，可以分解为灾害暴露性的“近岸高?远岸低”分异、交通敏感性的“外围高?中心低”分异、服务适应性的“中心与沿河高?外围低”兼“近港高?远港低”分异。同时发现：商业设施用地选址价值较高，在高可靠性选址中占比第一；中小学和社会福利设施用地选址价值最高，在高可靠性选址中占比第二；文化科研和娱乐康体设施用地在高可靠性选址中占比最小。针对临港城区实证研究结果，提出滨海城市竖向避难场所选址及可靠性提升对策。  相似文献   

游客-环境互动视角下旅游者目的地环境恢复性效应     

朱芳  苏勤  陶云  沈惊宏 《热带地理》2020,40(4):636-648

日常生活环境和旅游目的地环境都可以为个体提供恢复的机会，不同环境的属性特征导致不同程度的恢复。为了探究环境类型与恢复性效应之间的关系及停留时间的调节作用，文章采用问卷调查方式，利用配对样本t检验和混合设计方差分析相结合的方法，探讨游客在不同环境中的恢复性效应，并对这一现象提供心理上的解释。结果表明：1）恢复体验的4个维度（放松体验、心理脱离、掌握体验、控制体验）在旅游目的地环境中的得分均高于日常生活环境。2）掌握和控制体验维度在城市旅游目的地中的变化程度高于乡村旅游目的地，两种类型目的地的放松和心理脱离维度差异较小。3）随着在目的地停留时间的延长，乡村旅游目的地放松体验和心理脱离维度变化程度高于城市旅游目的地，两种类型目的地环境恢复性效应会相互靠近。因此，游客的环境恢复性效应不仅受到环境和目的地类型的影响，同时还与游客的适应程度有关，且受到其停留时间的调节作用。  相似文献