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西藏雅砻河流域生态系统服务价值地形梯度分异及驱动因素
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作者 周建伟 吴华 +8 位作者 许童 陈琳娜 孔玉忠 赵鑫永 郭齐韵 李佳潼 张泽林 朱康成 张晨光 《水土保持研究》 北大核心 2025年第2期396-406,共11页
[目的]分析雅砻河流域生态系统服务价值的变化,为流域生态文明建设提供科学依据。[方法]基于高精度土地利用数据,运用地形梯度分级、标准差椭圆和地理探测器,探究了近20年流域生态系统服务价值(Ecosystem service value,ESV)的时空演变... [目的]分析雅砻河流域生态系统服务价值的变化,为流域生态文明建设提供科学依据。[方法]基于高精度土地利用数据,运用地形梯度分级、标准差椭圆和地理探测器,探究了近20年流域生态系统服务价值(Ecosystem service value,ESV)的时空演变和地形梯度分异特征。[结果](1)草地是流域主要的土地利用类型,占比达92.45%。研究期内林地、灌木和草地面积有所减少,其他类型有所增加;(2)流域ESV在研究期间增长了0.13%(0.16亿元),ESV在空间上呈现出东南部高西北部低的特征。随着海拔、坡度和地形起伏度的抬升,ESV呈先增后降的分布规律,坡向梯度呈阴坡高于阳坡的特征。(3)流域ESV的标准差椭圆和重心在研究期内逐渐向西南方向移动,并趋于聚集。ESV的空间分异主要受自然和经济因子的影响,其中年均地温是主导因子(q=0.24),任意因子交互均增强了其分异性。[结论]依据雅砻河流域ESV的时空和地形分布特征,采取因地制宜的生态保护措施,促进流域生态环境的可持续发展。 展开更多
关键词 生态系统服务价值 地形梯度 空间分异 驱动因素 雅砻河流域
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Plankton community composition in the Three Gorges Reservoir Region revealed by PCR-DGGE and its relationships with environmental factors 被引量:27
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作者 YAN Qingyun YU Yuhe +2 位作者 FENG Weisong YU Zhigang CHEN Hongtao 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2008年第6期732-738,共7页
To explore the relationships between community composition and the environment in a reservoir ecosystem, plankton communities from the Three Gorges Reservoir Region were studied by PCR-denaturing gradient gel electrop... To explore the relationships between community composition and the environment in a reservoir ecosystem, plankton communities from the Three Gorges Reservoir Region were studied by PCR-denaturing gradient gel electrophoresis fingerprinting. Bacterial and eukaryotic operational taxonomic units (OTUs), generated by DGGE analysis of the PCR-amplified 16S and 18S rRNA genes, were used as surrogates for the dominant "biodiversity units". OTU composition among the sites was heterogeneous; 46.7% of the total bacterial OTUs (45) and 64.1% of the eukaryotic OTUs (39) were identified in less than half of the sampling sites. Unweighted pair group method with arithmetic averages (UPGMA) clustering of the OTUs suggested that the plankton communities in the Xiangxi Rive sites were not always significantly different from those from the Yangtze River sites, despite clear differences in their environmental characterizations. Canonical correspondence analysis (CCA) was applied to further investigate the relationships between OTU composition and the environmental factors. The first two CCA ordination axes suggested that the bacterial community composition was primarily correlated with the variables of NO3^--N, dissolved oxygen (DO), and SiO3^2--Si, whereas, the eukaryotic community was mainly correlated with the concentrations of DO, PO4^3--P, and SiO3^2--Si. 展开更多
关键词 plankton community environmental factors denaturing gradient gel electrophoresis (DGGE) spatial pattern Three Gorges Reservoir Region
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Research on the Distribution Law and Influencing Factors of Ground Temperature in Xutuan Coal Mine
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作者 Lintao Wang Qimeng Liu Sen Yang 《Journal of Geoscience and Environment Protection》 2020年第10期88-101,共14页
Taking the Xutuan coal mine as an example, based on the temperature measurement data, combined with the geological background of the study area, this paper analyzes the distribution, thermal evolution, formation mecha... Taking the Xutuan coal mine as an example, based on the temperature measurement data, combined with the geological background of the study area, this paper analyzes the distribution, thermal evolution, formation mechanism and influencing factors of the deep geothermal field in the study area. Combined with previous research results and field temperature measurement data, the research results show that the temperature gradient of Xutuan coal mine varies in the range of 2.65<span style="white-space:nowrap;">&deg;</span>C/hm - 3.15<span style="white-space:nowrap;">&deg;</span>C/hm, most of which are 1.6<span style="white-space:nowrap;">&deg;</span>C/hm - 3.0<span style="white-space:nowrap;">&deg;</span>C/hm, which belongs to the normal area with relatively stable geothermal gradient. The northern part of the study area is more developed than the southern part. The minimum geothermal gradient is 2.65<span style="white-space:nowrap;">&deg;</span>C/hm, and the geothermal gradient gradually increases from north to south;the geothermal gradient is negatively correlated with the buried depth within a certain depth range. Roughly taking the depth of 200 - 350 m as the dividing line, the temperature increases with the increase of depth, showing a good linear trend and the characteristics of conductive heating. The main influencing factor of the geothermal field in the study area is the geological structure, which is greatly affected by the fault structure. Followed by lithological changes and groundwater activities, the flow of the four waters has a certain control effect on the shallow geothermal field distribution. 展开更多
关键词 Geothermal Distribution Xutuan Coal Mine Geothermal gradient Influencing factors Geological Structure
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Drivers of coastal bacterioplankton community diversity and structure along a nutrient gradient in the East China Sea
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作者 HE Jiaying WANG Kai +4 位作者 XIONG Jinbo GUO Annan ZHANG Demin FEI Yuejun YE Xiansen 《Journal of Oceanology and Limnology》 SCIE CAS CSCD 2018年第2期329-340,共12页
Anthropogenic nutrient discharge poses widespread threats to coastal ecosystems and has increased environmental gradients from coast to sea. Bacterioplankton play crucial roles in coastal biogeochemical cycling, and a... Anthropogenic nutrient discharge poses widespread threats to coastal ecosystems and has increased environmental gradients from coast to sea. Bacterioplankton play crucial roles in coastal biogeochemical cycling, and a variety of factors af fect bacterial community diversity and structure. We used 16 S r RNA gene pyrosequencing to investigate the spatial variation in bacterial community composition(BCC) across five sites on a coast-of fshore gradient in the East China Sea. Overall, bacterial alpha-diversity did not diff er across sites, except that richness and phylogenetic diversity were lower in the of fshore sites, and the highest alpha-diversity was found in the most landward site, with Chl-abeing the main factor. BCCs generally clustered into coastal and of fshore groups. Chl-a explained 12.3% of the variation in BCCs, more than that explained by either the physicochemical(5.7%) or spatial(8.5%) variables. Nutrients(particularly nitrate and phosphate), along with phytoplankton abundance, were more important than other physicochemical factors, co-explaining 20.0% of the variation in BCCs. Additionally, a series of discriminant families(primarily affiliated with Gammaproteobacteria and Alphaproteobacteria), whose relative abundances correlated with Chl-a, DIN, and phosphate concentrations, were identified, implying their potential to indicate phytoplankton blooms and nutrient enrichment in this marine ecosystem. This study provides insight into bacterioplankton response patterns along a coast-of fshore gradient, with phytoplankton abundance increasing in the of fshore sites. Time-series sampling across multiple transects should be performed to determine the seasonal and spatial patterns in bacterial diversity and community structure along this gradient. 展开更多
关键词 BACTERIOPLANKTON PYROSEQUENCING nutrient gradient phytoplankton abundance dominant factor BIOINDICATOR
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Study of thermal properties of supraglacial debris and degree-day factors on Lirung Glacier,Nepal 被引量:1
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作者 Mohan Bahadur Chand Rijan Bhakta Kayastha 《Research in Cold and Arid Regions》 CSCD 2018年第5期357-368,共12页
The extensive debris that covers glaciers in the ablation zone of the Himalayan region plays an important part in regulating ablation rates and water availability for the downstream region. The melt rate of ice is det... The extensive debris that covers glaciers in the ablation zone of the Himalayan region plays an important part in regulating ablation rates and water availability for the downstream region. The melt rate of ice is determined by the amount of heat conducted through debris material lying over the ice. This study presents the vertical temperature gradients, thermal properties in terms of thermal diffusivity and thermal conductivity, and positive degree-day factors for the debris-covered portion of Lirung Glacier in Langtang Valley, Nepal Himalaya using field-based measurements from three different seasons.Field measurements include debris temperatures at different debris thicknesses, air temperature, and ice melt during the monsoon(2013), winter(2013), and pre-monsoon(2014) seasons. We used a thermal equation to estimate thermal diffusivity and thermal conductivity, and degree-day factors(DDF) were calculated from cumulative positive temperature and ice melt of the measurement period. Our analysis of debris temperature profiles at different depths of debris show the daily linear gradients of-20.81 °C/m, 4.05 °C/m, and-7.79 °C/m in the monsoon, winter, and pre-monsoon seasons, respectively. The values of thermal diffusivity and thermal conductivity in the monsoon season were 10 times greater than in the winter season. The large difference in these values is attributed to surface temperature and moisture content within the debris. Similarly, we found higher values of DDFs at thinner debris for the pre-monsoon season than in the monsoon season although we observed less melting during the pre-monsoon season. This is attributed to higher cumulative temperature during the monsoon season than in the pre-monsoon season. Our study advances our understanding of heat conductivity through debris material in different seasons, which supports estimating ice melt and discharge from glacierized river basins with debris-covered glaciers in the Himalayan region. 展开更多
关键词 Lirung Glacier HIMALAYA debris-covered glacier degree-day factor thermal conductivity temperature gradient
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考虑识别鲁棒性和虹膜颜色影响的瞳孔精准定位方法
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作者 罗亚波 李鑫 《南京大学学报(自然科学版)》 CAS CSCD 北大核心 2024年第1期97-105,共9页
准确的瞳孔定位广泛应用于疲劳监控、注意力分析、凝视跟踪等领域.当前,对于瞳孔定位的研究,还存在两个难点问题:(1)瞳孔检测的精准率受到图像分辨率、照明、头部姿态的影响,因而自然条件下的定位精准度较低;(2)虹膜颜色影响定位精准率... 准确的瞳孔定位广泛应用于疲劳监控、注意力分析、凝视跟踪等领域.当前,对于瞳孔定位的研究,还存在两个难点问题:(1)瞳孔检测的精准率受到图像分辨率、照明、头部姿态的影响,因而自然条件下的定位精准度较低;(2)虹膜颜色影响定位精准率,但当前对于不同虹膜颜色的瞳孔定位方法的研究还不完善.针对以上问题,提出一种新的适用于包含全脸图像的瞳孔定位方法.所提方法无需训练,可直接用于瞳孔定位任务.方法核心是将表示局部径向对称性的自相似性分数,与根据瞳孔和周围区域之间的梯度信息计算得到的眼部区域梯度辐射分数相结合,取联合分数峰值坐标为瞳孔中心.在BioID数据集和GI4E数据集上评估本方法.在归一化误差e≤0.05的情况下,准确率分别为94.67%(BioID),97.09%(GI4E),在e≤0.10的情况下,准确率分别为99.47%(BioID),99.51%(GI4E).所提方法在由低分辨率深色虹膜的人脸图像组成的自制数据集上准确率为98.66%(e≤0.05)和100%(e≤0.10),表明所提方法对于虹膜颜色有较好的鲁棒性. 展开更多
关键词 瞳孔定位 图像处理 自相似性 图像梯度 人因工程
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Plasma Nogo-A and placental growth factor levels are associated with portal hypertension in patients with liver cirrhosis 被引量:1
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作者 Sigita Gelman Violeta Salteniene +7 位作者 Andrius Pranculis Jurgita Skieceviciene Romanas Zykus Dalius Petrauskas Limas Kupcinskas Ali Canbay Alexander Link Juozas Kupcinskas 《World Journal of Gastroenterology》 SCIE CAS 2019年第23期2935-2946,共12页
BACKGROUND Clinically significant portal hypertension(CSPH) and severe portal hypertension(SPH) increase the risk for decompensation and life-threatening complications in liver cirrhosis. Pathologic angiogenesis might... BACKGROUND Clinically significant portal hypertension(CSPH) and severe portal hypertension(SPH) increase the risk for decompensation and life-threatening complications in liver cirrhosis. Pathologic angiogenesis might contribute to the formation of these conditions. Placental growth factor(PlGF) and Nogo-A protein are biomarkers of pathological angiogenesis, but data on their role in liver cirrhosis and portal hypertension is scarce.AIM To determine plasma levels of PlGF and Nogo-A in patients with liver cirrhosis,CSPH, SPH and potential to predict portal hypertension.METHODS A cohort of 122 patients with hepatitis C virus and/or alcohol-induced liver cirrhosis with characterized hepatic venous pressure gradient(HVPG) were included in the study. Demographic data, medical history, Child-Turcotte-Pugh and Model of End Stage liver disease score, clinical chemistry, liver stiffnessvalues were recorded on the day of the procedure prior HVPG measurement. The degree of portal hypertension was determined by the invasive HVPG measurement. Nogo-A and PlGF plasma levels were evaluated using enzyme linked immunosorbent assay. The control group consisted of 30 healthy age-and sex-matched individuals.RESULTS Peripheral PlGF levels were higher and Nogo-A levels were lower in patients with liver cirrhosis(23.20 vs 9.85;P < 0.0001 and 2.19 vs 3.12;P = 0.004 respectively). There was a positive linear correlation between peripheral levels of PlGF and HVPG(r = 0.338, P = 0.001) and negative linear correlation between the peripheral Nogo-A levels and HVPG(r =-0.267, P = 0.007). PlGF levels were higher in CSPH and SPH(P = 0.006;P < 0.0001) whereas Nogo-A levels were lower(P = 0.01;P < 0.033). Area under the curve for the diagnosis of CSPH for PlGF was 0.68(P = 0.003) and for Nogo-A-0.67(P = 0.01);for SPH 0.714(P <0.0001) and 0.65(P = 0.014) respectively. PlGF levels were higher and Nogo-A levels were lower in patients with esophageal varices(P < 0.05). PlGF cut-off value of 25 pg/mL distinguished patients with CSPH at 55.7% sensitivity and76.7% specificity;whereas Nogo-A cut-off value of 1.12 ng/mL was highly specific(93.1%) for the diagnosis of CSPH.CONCLUSION Plasma PlGF levels were higher while Nogo-A levels were lower in patients with liver cirrhosis and portal hypertension. Biomarkers showed moderate predictive value in determining CSPH and SPH. 展开更多
关键词 Liver CIRRHOSIS PORTAL hypertension Angiogenesis PLACENTAL growth factor NOGO-A Hepatic VENOUS pressure gradient
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Finite element analysis of thermal residual stresses at cemented carbide rock drill buttons with cobalt-gradient structure 被引量:3
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作者 黄自谦 贺跃辉 +2 位作者 蔡海涛 肖逸锋 黄伯云 《中国有色金属学会会刊:英文版》 EI CSCD 2008年第3期660-664,共5页
The aim of this study is to apply the concept of functionally graded materials(FGMs) to cemented carbides and to develop high-performance rock drill buttons. Cobalt-gradient structure was introduced to the surface zon... The aim of this study is to apply the concept of functionally graded materials(FGMs) to cemented carbides and to develop high-performance rock drill buttons. Cobalt-gradient structure was introduced to the surface zone of the buttons by carburizing process. Finite element method and XRD measurement were used to decide the distribution of thermal residual stress. Constitutive parameters were determined by constraint factor. Numerical results show that residual stresses of gradient buttons mainly concentrate in cobalt-gradient zone. There is compressive stress in the surface zone and tensile stress in the cobalt-rich zone. The maximum value of surface compressive stress is 180 MPa for WC-6Co cemented carbides. And the numerical results agree with the results of XRD measurement. 展开更多
关键词 超硬合金 钴梯度结构 有限元方法 约束因素
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Improved gradient iterative algorithms for solving Lyapunov matrix equations 被引量:1
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作者 顾传青 范伟薇 《Journal of Shanghai University(English Edition)》 CAS 2008年第5期395-399,共5页
In this paper, an improved gradient iterative (GI) algorithm for solving the Lyapunov matrix equations is studied. Convergence of the improved method for any initial value is proved with some conditions. Compared wi... In this paper, an improved gradient iterative (GI) algorithm for solving the Lyapunov matrix equations is studied. Convergence of the improved method for any initial value is proved with some conditions. Compared with the GI algorithm, the improved algorithm reduces computational cost and storage. Finally, the algorithm is tested with GI several numerical examples. 展开更多
关键词 gradient iterative (GI) algorithm improved gradient iteration (GI) algorithm Lyapunov matrix equations convergence factor
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ANTI-PLANE SHEAR CRACK IN A FUNCTIONALLY GRADIENT PIEZOELECTRIC MATERIAL 被引量:2
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作者 Hu Keqiang Zhong Zheng Jin Bo 《Acta Mechanica Solida Sinica》 SCIE EI 2002年第2期140-148,共9页
The main objective of this paper is to study the singular natureof the crack-tip stress and electric displacement field in afunctionally gradient piezoelectric medium having materialcoefficients with a discontinuous d... The main objective of this paper is to study the singular natureof the crack-tip stress and electric displacement field in afunctionally gradient piezoelectric medium having materialcoefficients with a discontinuous derivative. The problem isconsidered for the simplest possible loading and geometry, namely,the anti-plane shear stress and electric displacement in -plane oftwo bonded half spaces in which the crack is parallel to theinterface. 展开更多
关键词 functionally gradient material piezoelectric material stress intensityfactors electric dis- placement intensity factors
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铁路轨道工程物化阶段碳排放预测及影响因素研究
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作者 鲍学英 韩通 霍雨雨 《铁道科学与工程学报》 EI CAS CSCD 北大核心 2024年第10期4299-4310,共12页
在国家“双碳”战略目标下,铁路领域低碳转型势在必行。轨道工程作为铁路工程的重要组成部分,其物化阶段产生的碳排放是铁路工程碳排放的重要来源。为量化铁路轨道工程物化阶段碳排放,并实现智能化分析,建立铁路轨道工程物化阶段碳排放... 在国家“双碳”战略目标下,铁路领域低碳转型势在必行。轨道工程作为铁路工程的重要组成部分,其物化阶段产生的碳排放是铁路工程碳排放的重要来源。为量化铁路轨道工程物化阶段碳排放,并实现智能化分析,建立铁路轨道工程物化阶段碳排放计算模型,并提出一种基于机器学习算法的碳排放预测及影响因素分析模型。首先,界定物化阶段研究边界,分解铁路轨道工程,以主要工序为基本计算单元,采用碳排放因子法建立碳排放计算模型;其次,运用梯度提升树算法(Light Gradient Boosting Machine,LigtGBM)构建碳排放预测模型,并引入可解释机器学习模型(Shapley Addictive Explanation,SHAP)分析影响因素对碳排放量的贡献。以某西南山区铁路轨道工程为例,选取其中典型单元轨节计算碳排放量,结果显示1 km长度碳排放总量为1290.94 t,物化阶段中材料生产阶段碳排放占比最大,约为87.21%;分项工程中铺轨和铺道床的碳排放占比较高,分别为47.44%和46.44%。提取该轨道工程碳排放相关特征作为影响因素,对LigtGBM-SHAP模型进行验证,各项评估指标的数值表明模型具有较好的预测效果,影响因素重要度由大到小依次为轨道结构形式、线路地段、轨枕类型或轨道板、施工天数、区段坡度、区段运输距离,并在结果分析中通过单因素特征依赖图明晰各影响因素的分类变量或数值变化对碳排放量产生的影响。研究成果为铁路轨道工程碳排放计算、预测及分析提供了一个更加智能、全面的研究模型,为铁路工程建设进行碳减排工作提供参考。 展开更多
关键词 物化阶段 碳排放预测 影响因素 梯度提升树算法 可解释机器学习
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医院干细胞实验室室内外环境压差影响因素分析
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作者 马倩 张玉彬 《医用气体工程》 2024年第3期21-25,共5页
干细胞实验室是从事干细胞基础研究、制剂制备、技术开发和医疗服务的重要场所。目前,干细胞实验室的建设总体原则主要参照2010版《药品生产质量管理规范》、《医院洁净手术部建筑技术规范》(GB 50333-2002)等规范标准。在交付科室投人... 干细胞实验室是从事干细胞基础研究、制剂制备、技术开发和医疗服务的重要场所。目前,干细胞实验室的建设总体原则主要参照2010版《药品生产质量管理规范》、《医院洁净手术部建筑技术规范》(GB 50333-2002)等规范标准。在交付科室投人使用后,其压差梯度的控制对于临床细胞培养尤为重要。影响压差梯度的内外因素有很多,本文以某医院干细胞实验室项目为例,对影响干细胞实验室核心区室内外环境压差的主要影响因素进行分析。 展开更多
关键词 干细胞实验室 药品生产质量管理规范 压差梯度 影响因素
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Modified projective synchronization with complex scaling factors of uncertain real chaos and complex chaos
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作者 张芳芳 刘树堂 余卫勇 《Chinese Physics B》 SCIE EI CAS CSCD 2013年第12期141-151,共11页
To increase the variety and security of communication, we present the definitions of modified projective synchronization with complex scaling factors (CMPS) of real chaotic systems and complex chaotic systems, where... To increase the variety and security of communication, we present the definitions of modified projective synchronization with complex scaling factors (CMPS) of real chaotic systems and complex chaotic systems, where complex scaling factors establish a link between real chaos and complex chaos. Considering all situations of unknown parameters and pseudo-gradient condition, we design adaptive CMPS schemes based on the speed-gradient method for the real drive chaotic system and complex response chaotic system and for the complex drive chaotic system and the real response chaotic system, respectively. The convergence factors and dynamical control strength are added to regulate the convergence speed and increase robustness. Numerical simulations verify the feasibility and effectiveness of the presented schemes. 展开更多
关键词 modified projective synchronization complex scaling factors complex chaotic systems speed-gradient method
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基于STL-XGBoost-NBEATSx的小时天然气负荷预测
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作者 邵必林 任萌 田宁 《中国石油大学学报(自然科学版)》 EI CAS CSCD 北大核心 2024年第3期170-179,共10页
小时天然气负荷预测受外部特征因素与预测方法的影响,为提高其预测精度并解决其他深度学习类模型或组合模型可解释性差、训练时间过长的问题,在引入“小时影响度”这一新特征因素的同时提出一种基于极端梯度提升树(extreme gradient boo... 小时天然气负荷预测受外部特征因素与预测方法的影响,为提高其预测精度并解决其他深度学习类模型或组合模型可解释性差、训练时间过长的问题,在引入“小时影响度”这一新特征因素的同时提出一种基于极端梯度提升树(extreme gradient boosting tress,XGBoost)模型与可解释性神经网络模型NBEATSx组合预测的方法;以XGBoost模型作为特征筛选器对特征集数据进行筛选,再将筛选降维后的数据集输入到NBEATSx中训练,提高NBEATSx的训练速度与预测精度;将负荷数据与特征数据经STL(seasonal and trend decomposition using Loess)算法分解为趋势分量、季节分量与残差分量,再分别输入到XGBoost中进行预测,减弱原始数据中的噪音影响;将优化后的NBEATSx与XGBoost模型通过方差倒数法进行组合,得出STL-XGBoost-NBEATSx组合模型的预测结果。结果表明:“小时影响度”这一新特征是小时负荷预测的重要影响因素,STL-XGBoost-NBEATSx模型训练速度有所提高,具有良好的可解释性与更高的预测准确性,模型预测结果的平均绝对百分比误差、均方误差、平均绝对误差分别比其余单一模型平均降低54.20%、63.97%、49.72%,比其余组合模型平均降低24.85%、34.39%、23.41%,模型的决定系数为0.935,能够很好地拟合观测数据。 展开更多
关键词 天然气负荷预测 小时影响因素 极端梯度提升树 可解释性 NBEATSx 组合模型
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考虑用户负荷率因素的电力市场偏差电量定价方法
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作者 王蕾 徐绮 +3 位作者 黎新 薄小永 李泠聪 王鹏 《电子设计工程》 2024年第17期112-116,共5页
针对偏差电量定价中尚未考虑用户的负荷率变化,导致电力交易各方的经济利益不均衡问题,提出考虑用户负荷率因素的电力市场偏差电量定价方法。以售电量时间序列为基准,完成基于多元线性回归的电力市场售电量预测。在此基础上,建立基于月... 针对偏差电量定价中尚未考虑用户的负荷率变化,导致电力交易各方的经济利益不均衡问题,提出考虑用户负荷率因素的电力市场偏差电量定价方法。以售电量时间序列为基准,完成基于多元线性回归的电力市场售电量预测。在此基础上,建立基于月用电量偏差率的惩罚机制,考虑负荷率和偏差率的变化确定对应偏差电量的电价。通过某区域电力市场交易数据试验,负荷率的波动直接影响购电公司收益,提出的偏差电量定价方法能够降低偏差考核电费对整体收益的影响,规范电量市场交易行为,在一定程度上均衡用户和售电企业各方的利益。 展开更多
关键词 负荷率 偏差电量 多元线性回归 梯度下降
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贺兰山土壤微生物生物量C、N、P化学计量特征沿海拔梯度的变化规律及其影响因素
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作者 王思瑶 王玉娟 +9 位作者 邱开阳 李小聪 邱爱珍 朱亚超 张硕 司浩宇 张焱清 冯家琳 冯占荣 冯绍蕾 《草业科学》 CAS CSCD 北大核心 2024年第7期1558-1570,共13页
土壤微生物生物量作为土壤中活的有机质部分,是评价土壤有机养分循环通量和周期的重要生态指标。探究干旱半干旱山地生态系统土壤微生物生物量C、N、P生态化学计量特征的垂直分异规律及其关键影响因素,可为了解干旱半干旱山地生态系统土... 土壤微生物生物量作为土壤中活的有机质部分,是评价土壤有机养分循环通量和周期的重要生态指标。探究干旱半干旱山地生态系统土壤微生物生物量C、N、P生态化学计量特征的垂直分异规律及其关键影响因素,可为了解干旱半干旱山地生态系统土壤C、N、P循环过程及调控机制提供参考。本研究以宁夏贺兰山不同海拔6个典型地带性植被类型作为研究对象,分别测定土壤微生物生物量碳(MBC)、微生物生物量氮(MBN)、微生物生物量磷(MBP)含量和土壤有机碳(SOC)、全氮(TN)、全磷(TP)含量,并运用单因素方差分析、冗余分析、方差分解分析等分析方法,解析土壤微生物生物量C、N、P生态化学计量特征的垂直分异特征与气候因子和土壤理化因子之间的关系。结果表明:1)土壤微生物生物量C、N、P含量沿海拔变化差异显著(P<0.05),MBC、MBP含量随海拔升高呈现先上升后下降的变化趋势,MBN随海拔升高呈上升趋势,三者均于亚高山灌丛处含量最高,含量分别为1502.08、35.42和127.55 mg·kg^(-1);2)MBC:MBP、MBN:MBP、MBC:MBN均随海拔升高呈现波动变化趋势,MBC:MBP、MBN:MBP在浅山灌丛处有最大值;3)冗余分析与方差分解分析显示,TN、年均温度(MAT)、pH、TN:TP是显著影响土壤微生物生物量C、N、P生态化学计量特征的因子(P<0.05),土壤理化因子较海拔、气候因子对土壤微生物生物量C、N、P生态化学计量特征的影响更大。研究结果表明,土壤理化因子的变化能够引起土壤微生物生物量C、N、P生态化学计量特征的显著变化。 展开更多
关键词 贺兰山 海拔梯度 土壤因子 土壤微生物生物量 生态化学计量特征
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不同纬度植物群落系统发育与功能性状结构研究 被引量:3
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作者 苗乐乐 刘旻霞 +3 位作者 肖音迪 杨春亮 王千月 王敏 《生态学报》 CAS CSCD 北大核心 2024年第1期317-329,共13页
研究植物群落系统发育和功能性状结构有助于了解植物多样性维持机制及物种间的亲缘关系。甘肃省地理环境复杂,显著而多变的气候梯度形成了区域植被和环境差异,丰富了栖息地类型,具有显著的纵向连通性和纬度隔离性,以甘肃省典型纬度梯度... 研究植物群落系统发育和功能性状结构有助于了解植物多样性维持机制及物种间的亲缘关系。甘肃省地理环境复杂,显著而多变的气候梯度形成了区域植被和环境差异,丰富了栖息地类型,具有显著的纵向连通性和纬度隔离性,以甘肃省典型纬度梯度植物群落为研究对象,通过对其进行群落学调查和功能性状测定,计算净亲缘关系指数(Net relatedness index, NRI)和平均成对性状距离(Mean pairwise trait distance, PW)来分析植物群落系统发育结构和功能性状格局对不同纬度的响应。结果表明:(1) Shannon-Weiner多样性指数,物种丰富度,谱系α多样性指数表现出随纬度增加而显著降低的变化趋势(P<0.05),Pielou均匀度指数随纬度的升高没有显著的变化趋势;(2)系统发育结构在高、低纬度上趋于发散状态(NRI<0),在中纬度上又表现出聚集(NRI>0)的谱系结构,表明种间竞争作用减弱,环境过滤作用逐渐增强,随纬度继续升高相似性限制作用在物种聚集过程中占优势;而群落的功能性状结构随着纬度增加表现出与谱系结构相反的状态,因此植物群落的系统发育和功能性状结构不一致;(3)植物高度表现出微弱的系统发育信号(P<0.05),其他性状均未表现出显著的系统发育信号,表明植物功能性状受环境因素影响大,与系统发育关系不大。总体而言,甘肃省典型纬度梯度植物群落物种多样性维持机制由确定性过程主导,支持生态位理论,其中环境过滤和竞争排斥作用在大多数群落物种聚集过程中占优势地位。土壤含水量、土壤酸碱度和年平均气温等环境因子对植物性状格局影响较大,本研究有助于了解不同气候带植物多样性的地理分布格局和潜在的生态维持机制。 展开更多
关键词 纬度梯度 系统发育结构 功能性状 环境因子 系统发育信号
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A new calculation approach of wellbore separation factor based on the relative position of adjacent wells
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作者 HONG Difeng TANG Xueping +3 位作者 GAO Wenkai MAO Weimin WANG Peng LIU Ke 《Petroleum Exploration and Development》 2020年第1期196-203,共8页
As the current calculation methods for wellbore separation factor have some deficiencies, we propose and analyze a new calculation approach for wellbore separation factor based on the relative position of adjacent wel... As the current calculation methods for wellbore separation factor have some deficiencies, we propose and analyze a new calculation approach for wellbore separation factor based on the relative position of adjacent wellbores, named as relative position method for short. Based on the trajectory error ellipsoid model of single wellbore, the error ellipsoids model of adjacent wellbore was derived considering the correlation of trajectory errors between adjacent wells. Furthermore, the calculation formula of the separation factor based on relative position of adjacent wellbore was derived and solved with the conjugate gradient algorithm. Case study shows that the new approach is more precise and higher in applicability than the ellipsoid scaling method and the minimum distance method, it can evaluate the state of well collision more reasonably. By doing batch calculation with the new method and following the criterion of well collision avoidance, the permissible ranges of key parameters in the well design can be worked out quickly. This method has good application in the design of cluster wells and directional wells. 展开更多
关键词 wellhole separation factor wellhole COLLISION AVOIDANCE RELATIVE wellbores error CONJUGATE gradient algorithm cluster WELLS
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专精特新企业成长与培育的研究回顾与未来研究展望 被引量:7
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作者 张延平 王满四 +1 位作者 黄敬伟 罗勇根 《科学决策》 CSSCI 2024年第2期155-175,共21页
专精特新企业高质量成长与培育正成为新兴热点研究主题。已有研究对其概念、成长因素、培育路径等内容进行了初步探讨,但仍然缺乏系统梳理和深入分析。基于此,本研究聚焦于专精特新企业的成长与培育这一研究主题进行梳理分析。首先,界... 专精特新企业高质量成长与培育正成为新兴热点研究主题。已有研究对其概念、成长因素、培育路径等内容进行了初步探讨,但仍然缺乏系统梳理和深入分析。基于此,本研究聚焦于专精特新企业的成长与培育这一研究主题进行梳理分析。首先,界定了专精特新企业的概念,阐释了梯次分类法和波特竞争战略分类法两种视角下的专精特新企业分类;其次,基于“动因-过程-结果”的逻辑主线,构建专精特新企业成长与培育的理论框架,通过与德国隐形冠军企业进行对比分析,揭示了我国专精特新企业成长与培育的动因;梳理出专精特新企业成长与培育过程中的五个关键因素,解释了专精特新企业成长与培育的过程;总结出四种培育模式和与此相匹配的四种梯度培育路径,呈现了专精特新企业成长与培育的结果。最后,构建了专精特新企业成长与培育整合的理论框架,提出专精特新企业成长与培育的管理启示和未来展望,为专精特新企业高质量发展提供理论参考和实践依据。 展开更多
关键词 专精特新企业 成长因素 培育模式 梯度培育
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高温热冲击下花岗岩内一维热传导规律试验研究
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作者 李晓科 郤保平 +3 位作者 蔡佳豪 解瑾 贾鹏 马骁 《岩土工程学报》 EI CAS CSCD 北大核心 2024年第10期2192-2201,共10页
热对岩石物理力学性质的劣化作用受岩石的结构、矿物组成及分布等多方面因素共同决定。为解决工程中存在的半无限大物体经历高温热冲击时其内部的一维热传导问题,通过设置高温热冲击试验,对热冲击过程中的温度场、升温速率、温度梯度场... 热对岩石物理力学性质的劣化作用受岩石的结构、矿物组成及分布等多方面因素共同决定。为解决工程中存在的半无限大物体经历高温热冲击时其内部的一维热传导问题,通过设置高温热冲击试验,对热冲击过程中的温度场、升温速率、温度梯度场进行分析,并引入热冲击因子来定量表征高温热冲击过程中热对岩石的破坏程度,探讨热源温度及介质对花岗岩传热的影响,研究结果表明:不同冲击温度下花岗岩内温度变化均分为3个阶段:快速升温阶段、缓慢升温阶段、稳定阶段;由于花岗岩的非均质性,高温热冲击下花岗岩内温度场和温度梯度场分布均具有紊乱性,且温度梯度场紊乱程度高于温度场;高温热冲击过程中热冲击因子在花岗岩内的分布具有明显的非均质性,且其波峰具有动态移动的性质;100℃时,水相对硅油具有更大的对流换热系数,此状态下花岗岩内温度、升温速率、温度梯度均具有更大的峰值且更早进入稳定阶段。 展开更多
关键词 花岗岩 热冲击 温度场 温度梯度场 热冲击因子
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