期刊文献+
共找到23篇文章
< 1 2 >
每页显示 20 50 100
The influence of selective cutting of mixed Korean pine(Pinus koraiensis Sieb.et Zucc.) and broad-leaf forest on rare species distribution patterns and spatial correlation in Northeast China 被引量:4
1
作者 Binbin Kan Qingcheng Wang Wenjuan Wu 《Journal of Forestry Research》 SCIE CAS CSCD 2015年第4期833-840,共8页
This study aimed to demonstrate change in spatial correlation between Korean pine (Pinus koraiensis Sieb. et Zucc.) and three rare species, and change in spatial distribution of four species in response to a range o... This study aimed to demonstrate change in spatial correlation between Korean pine (Pinus koraiensis Sieb. et Zucc.) and three rare species, and change in spatial distribution of four species in response to a range of selective cutting intensities. We sampled three plots of mixed Korean pine and broad-leaf forest in Lushuihe Forestry Bureau of Jilin province, China. Plot 1, a control, was unlogged Korean pine broad-leaf forest. In plots 2 and 3, Korean pine was selectively cut at 15 and 30 % intensity, respectively, in the 1970s. Other species were rarely cut. We used point-pattern analysis to research the spatial distributions of four tree species and quantify spatial correlations between Korean pine and the other three species, Amur linden (Tilia amurensis Rupr.), Manchurian ash (Fraxinus mandshurica Rupr.), and Mongolian oak (Quercus mongolica Fisch.) in all three plots. The results of the study show that selective cutting at 15 % intensity did not significantly change either the species spatial patterns or the spatial correlation between Korean pine and broadleaf species. Selective cutting at 30 % intensity slightly affected the growth of Korean pine and valuable species in forest communities, and the effect was considered nondestructive and recoverable. 展开更多
关键词 Korean pine broad-leaf forest Cuttingintensity Rare species spatial pattern - spatialcorrelation
下载PDF
Population Spatial Distribution Based on Luojia 1-01 Nighttime Light Image:A Case Study of Beijing 被引量:1
2
作者 SUN Lu WANG Jia CHANG Shuping 《Chinese Geographical Science》 SCIE CSCD 2021年第6期966-978,共13页
With the continuous development of urbanization in China,the country’s growing population brings great challenges to urban development.By mastering the refined population spatial distribution in administrative units,... With the continuous development of urbanization in China,the country’s growing population brings great challenges to urban development.By mastering the refined population spatial distribution in administrative units,the quantity and agglomeration of population distribution can be estimated and visualized.It will provide a basis for a more rational urban planning.This paper takes Beijing as the research area and uses a new Luojia1-01 nighttime light image with high resolution,land use type data,Points of Interest(POI)data,and other data to construct the population spatial index system,establishing the index weight based on the principal component analysis.The comprehensive weight value of population distribution in the study area was then used to calculate the street population distribution of Beijing in 2018.Then the population spatial distribution was visualize using GIS technology.After accuracy assessments by comparing the result with the WorldPop data,the accuracy has reached 0.74.The proposed method was validated as a qualified method to generate population spatial maps.By contrast of local areas,Luojia 1-01 data is more suitable for population distribution estimation than the NPP/VIIRS(Net Primary Productivity/Visible infrared Imaging Radiometer)nighttime light data.More geospatial big data and mathematical models can be combined to create more accurate population maps in the future. 展开更多
关键词 Luojia1-01 nighttime light image principal component analysis points of interest landuse type data population spatial distribution
下载PDF
Spatial distribution of SiCln (n=O-2) in SICl4 plasma measured by mass spectroscopy
3
作者 王照奎 林揆训 +2 位作者 娄艳辉 林璇英 祝祖送 《Chinese Physics B》 SCIE EI CAS CSCD 2006年第10期2374-2377,共4页
For a better understanding of the deposition mechanism of thin films in SiCl4 source gas, we have measured the spatial distributions of SiCln (n=0-2) radicals in SICl4 radio frequency glow discharge plasma utilizing... For a better understanding of the deposition mechanism of thin films in SiCl4 source gas, we have measured the spatial distributions of SiCln (n=0-2) radicals in SICl4 radio frequency glow discharge plasma utilizing a mass spectrometer equipped with a movable gas sampling apparatus. The experimental results demonstrate that the relative densities of SiCln (n=0-2) radicals have peak values at the position of 10 mm above the powered electrode along the axial direction; the relative densities of the Si and SiCIn (n=1, 2) radicals have peak values at the positions of 27mm and 7 mm away from the axis along the radial direction, respectively. Generally speaking, in the whole SICl4 plasma bulk region, the relative density of Si is one order of magnitude higher than that of SICl, and the relative density of SiCl is several times higher than that of SICl2. This reveals that Si and SiCl may be the primary growth precursors in forming thin films. 展开更多
关键词 SiCln (n=0-2) neutral radicals spatial distribution mass spectrometric diagnosis
下载PDF
基于Oracle Spatial的GIS数据组织及查询 被引量:8
4
作者 苏炳均 诸昌钤 李林 《计算机应用研究》 CSCD 北大核心 2006年第12期278-280,共3页
G IS的一个难点是实现空间数据和属性数据的一体化存储和管理,研究用Oracle Spatial技术来解决这个问题。在确定了采用对象—关系模型来存储G IS数据后,比较了空间数据的两种导入方式,在此基础上,选用EasyLoader工具将G IS数据导入到Ora... G IS的一个难点是实现空间数据和属性数据的一体化存储和管理,研究用Oracle Spatial技术来解决这个问题。在确定了采用对象—关系模型来存储G IS数据后,比较了空间数据的两种导入方式,在此基础上,选用EasyLoader工具将G IS数据导入到Oracle数据库中,再用四元树索引为其建立索引。最后,选择Java作为开发工具,采用JDBC方式与Oracle数据库相连并实现了对G IS数据的查询。 展开更多
关键词 GIS数据 ORACLE spatial 对象-关系模型 四元树索引 查询
下载PDF
基于Oracle Spatial的矿山数据空间数据库的设计 被引量:2
5
作者 张珊 谭海樵 朱宇鹏 《地理空间信息》 2007年第2期91-93,共3页
分析了Oracle Spatial统一管理空间数据和属性数据的方法及优缺点,并介绍了Oracle 10g及Spatial的新特性。在此基础上给出了建立基于Oracle的对象-关系数据模型的适合统一存储和管理矿山数据的空间数据库的具体步骤和方法。
关键词 对象-关系数据模型 ORACLE spatial 矿山数据
下载PDF
基于Oracle Spatial的矿山数据空间数据库的设计 被引量:5
6
作者 张珊 谭海樵 朱宇鹏 《四川测绘》 2006年第2期76-78,71,共4页
分析了Oracle Spatial统一管理空间数据和属性数据的方法及优缺点,并介绍了Oracle 10g及Spatial的新特性。在此基础上,给出了建立基于Oracle的对象-关系数据模型的适合统一存储和管理矿山数据的空间数据库的具体步骤和方法。
关键词 对象-关系数据模型 ORACLE spatial 矿山数据
下载PDF
基于Oracle Spatial的GIS数据一体化存储模型及在城镇地籍调查中的应用 被引量:2
7
作者 潘红平 吴艳 《测绘》 2009年第5期233-237,共5页
本文主要围绕Oracle Spatial的对象-关系模型阐述了GIS数据一体化存储模型,并用具体实例分析了模型在城镇地籍调查中的应用。
关键词 ORACLE spatial GIS数据一体化存储模型 对象-关系模型 城镇地籍调查
下载PDF
Oracle Spatial设计林业空间数据库初探
8
作者 陈宇晖 《广东农业科学》 CAS CSCD 北大核心 2009年第12期207-209,共3页
林业空间数据库建设是林业信息化建设中的核心部分,建设的好坏直接影响林业信息化建设的效果。本文首先介绍和分析了Oracle 10g及Spatial模块特点。在此基础上,给出了建立基于Oracle的对象-关系数据模型的适合统一存储和管理林业数据的... 林业空间数据库建设是林业信息化建设中的核心部分,建设的好坏直接影响林业信息化建设的效果。本文首先介绍和分析了Oracle 10g及Spatial模块特点。在此基础上,给出了建立基于Oracle的对象-关系数据模型的适合统一存储和管理林业数据的空间数据库的步骤和方法。 展开更多
关键词 ORACLE spatial 林业数据库 对象-关系模式
下载PDF
Integrated use of GIS, remote sensing and multi-criteria decision analysis to assess ecological land suitability in multi-functional forestry 被引量:5
9
作者 Naser Ahmadi Sani Sasan Babaie Kafaky +1 位作者 Timo Pukkala Asadollah Mataji 《Journal of Forestry Research》 SCIE CAS CSCD 2016年第5期1127-1135,共9页
The Zagros forests are a treasure of valuable oak forests, but they have been severely degraded from long-term misuse. Geographic information systems (GIS) and multi-criteria decision analysis (MCDA) have been inc... The Zagros forests are a treasure of valuable oak forests, but they have been severely degraded from long-term misuse. Geographic information systems (GIS) and multi-criteria decision analysis (MCDA) have been increasingly used to improve the management of vulnerable ecosystems to prevent further degradation and increase the sustainability of land use. This study presents a methodology to assess land suitability using remote sensing (RS) to obtain wall-to-wall data for the calculations, GIS to analyze the data, and MCDA to rank alternative land uses. The criteria and subcriteria affecting the suitability of land for different uses were identified and weighted using an analytic hierarchy process. Variables used as subcriteria were assessed using satellite data and other sources of information such as existing maps and field surveys. Numerical values for the subcriteria were classified, and each class was given a priority rating according to expert judgments. Based on the ratings and weights of the subcriteria, a priority map was created for each land use using the weighted linear combination method. The priority maps for different land uses were overlaid to obtain a preliminary land use map, which often indicated several simultaneous land uses for the same location. The preliminary map was further edited by removing unrealistic, mutually exclusive land-use combinations. The study tested and demonstrated the potential of integrating RS, G1S and MCDA techniques for solving complicated land allocation problems in forested regions using a scientifically sound and practical approach for efficient and sustainable allocation of forestland for different uses. 展开更多
关键词 Analytic hierarchy process Decisionanalysis Ecological suitability Land allocation Land-use planning - spatial analysis - Zagros forests
下载PDF
Spatial resolved temperature measurement based on absorption spectroscopy using a single tunable diode laser 被引量:3
10
作者 Xilong Yu Fei Li Lihong Chen Xinyu Zhang 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2010年第1期147-149,共3页
A novel method based on wavelength-multiplexed line-of-sight absorption and profile fitting for nonuniform flow field measurement is reported. A wavelength scanning combing laser temperature and current modulation WMS... A novel method based on wavelength-multiplexed line-of-sight absorption and profile fitting for nonuniform flow field measurement is reported. A wavelength scanning combing laser temperature and current modulation WMS scheme is used to implement the wavelength-multi- plexed-profile fitting method. Second harmonic (2f) signal of eight H20 transitions features near 7,170 cm^-1 are measured in one period using a single tunable diode laser. Spatial resolved temperature distribution upon a CH4/air premixed flat flame burner is obtained. The result validates the feasibility of strategy for non-uniform flow field diagnostics by means of WMS-2f TDLAS. 展开更多
关键词 WMS-2fTDLAS - Profile fitting spatial resolved - Temperature measurement
下载PDF
Seasonal and Spatial Variation of Radiative Effects of Anthropogenic Sulfate Aerosol 被引量:1
11
作者 钱云 汪宏七 +1 位作者 符淙斌 王自发 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 1998年第3期98-110,共13页
On the basis of the emission data of the industrial sulphur dioxide (SO_2) and observed climate fields over East Asia, the distribution of anthropogenic sulfate aerosol(SO_4~2-) with seasonal variation in the troposph... On the basis of the emission data of the industrial sulphur dioxide (SO_2) and observed climate fields over East Asia, the distribution of anthropogenic sulfate aerosol(SO_4~2-) with seasonal variation in the troposphere is simulated and analyzed by a regional sulfur transport model, and the direct radiative effects of SO_4~2- under different weather conditions are also calculated using the discrete ordinate method. The results show that the concentration of SO_4~2- has significant seasonal and spatial variations resulting from the effects of SO_2 emission source and precipitation and wind fields. Both the concentration of SO_2 and its radiative forcing have the largest values in October and the lowest in July. SO_4~2- causes the decrease of the radiation flux absorbed by earth-atmosphere and the cooling of air temperature by scattering more solar radiation back into space. Besides, the radiative and climatic effects of SO_4~2- are related to the types and height and optical thickness, etc., of the clouds. 展开更多
关键词 Sulfate aerosol(SO_4~2-) Radiative effects Seasonal and spatial variations
下载PDF
Obtaining vehicle parameters from bridge dynamic response:a combined semi-analytical and particle filtering approach 被引量:1
12
作者 R.Lalthlamuana S.Talukdar 《Journal of Modern Transportation》 2015年第1期50-66,共17页
Dynamic load imposed on the bridge by mov- ing vehicle depends on several bridge-vehicle parameters with various uncertainties. In the present paper, particle filter technique based on conditional probability has been... Dynamic load imposed on the bridge by mov- ing vehicle depends on several bridge-vehicle parameters with various uncertainties. In the present paper, particle filter technique based on conditional probability has been used to identify vehicle mass, suspension stiffness, and damping including tyre parameters from simulated bridge accelerations at different locations. A closed-form expres- sion is derived to generate independent response samples for the idealized bridge-vehicle coupled system consider- ing spatially non-homogeneous pavement unevenness. Thereafter, it is interfaced with the iterative process of particle filtering algorithm. The generated response sam- ples are contaminated by adding artificial noise in order to reflect field condition. The mean acceleration time history is utilized in particle filtering technique. The vehicle- imposed dynamic load is reconstructed with the identified parameters and compared with the simulated results. The present identification technique is examined in the presence of different levels of artificial noise with bridge response simulated at different locations. The effect of vehicle velocity, bridge surface roughness, and choice of prior probability density parameters on the efficiency of the method is discussed. 展开更多
关键词 Dynamic load - Particle filter - Forwardsolution spatially non-homogeneous Conditionalprobability
下载PDF
Osthole prevents cognitive impairment through modulating neuron cells in Aβ25-35-injected mice
13
作者 HOU Xue-qin 《中国药理学与毒理学杂志》 CAS 北大核心 2019年第6期417-418,共2页
OBJECTIVE To investigate the effects of osthole on learning and memory impairment of AD mice induced by injection of Aβ25-35 and the content of Ca2+, GLU and Aβ1-42 in the brain tissue and peripheral blood. METHODS ... OBJECTIVE To investigate the effects of osthole on learning and memory impairment of AD mice induced by injection of Aβ25-35 and the content of Ca2+, GLU and Aβ1-42 in the brain tissue and peripheral blood. METHODS Mice were randomly assigned to sham operation, Aβ25-35, Aβ25-35+Ost-L,Aβ25-35+Ost-M, and Aβ25-35+Ost-H group. Water maze test was performed to assessing spatial learning ability of mice. It is determined that the MDA level and the activity of SOD in the brain tissue of mice in each group by colorimetry. The GLU kit and Ca2 +kit were used to detect the GLU, Ca2 +in tissue and serum. ELISA was used to detect the expression of Aβ1-42 in the hippocampus and serum of mice. HE staining and silver staining were used to detect neuron apoptosis and pathological changes in brain slices and so on. RESULTS(1) Effects of osthole on learning and memory: With the increase of training day,the escape latencies continuously reduced in each experimental group, the escape latencies of the model group was longer on the 1 st, 2 nd, 3 rd, and 5 thdays than the normal group, the difference was statistically significant(day 3 and 4: P<0.05, day 5: P<0.01);compared with the model group, the escaping latency on the 5 thday of the OST low-medium high-dose group was significantly shortened, which was statistically significant(P<0.05).(2) Effects on oxidative stresspathway: the SOD activity of AD mice in the hippocampus model group was lower than that in the normal group, which was statistically significant(P<0.05);The SOD activity in the OST group was higher than that in the model group, which was statistically significant(P<0.05). The MDA content in the model group was significantly higher than that in the normal group(P<0.05). The MDA content in the OST high-dose group was lower than that in the model group, which was statistically significant(P<0.05).(3) Effects of GLU levels on neurotransmitters:the results of the detection of GLU in cortical area and GLU in serum of AD mice in OST dose groups showed that serum GLU levels in the model group were significantly lower than those in the sham group, which was statistically significant(P<0.05). GLU levels in the cortical area were also significantly higher than those in the sham group, which was statistically significant(P<0.05). Compared with the model group, GLU levels in the OST administration group were significantly down-regulated. Among the serum, the effect of medium dose group was obvious. Although there was a trend of down-regulation in the cortical administration group, there was no statistical significance.(4) Changes in Ca2+concentration in the brain. Detection of intracellular Ca2 +concentration in AD mice by OST doses showed that,compared with the sham group, the model group was significantly upregulated in cortical Ca2 +levels.There was no statistical difference in the administration group. Compared with the model group, the concentration of Ca2+in the OST-H group significantly decreased.(5) Effect on levels of Aβ1-42 in hippocampus and serum: model group had significantly higher Aβ1-42 levels in hippocampus than in sham operation group, which was statistically significant(P<0.05). Aβ1-42 in serum was also significantly upregulated compared to the sham group, which was statistically significant(P<0.05). Compared with the model group, the levels of Aβ1-42 in the OST administration group were significantly down-regulated,with the lower and middle doses in the hippocampus being more significant, while the serum was more pronounced at lower doses.(6) Silver staining to detect the tangles of hippocampal neurons: Neuron tangles in the hippocampal CA1 region showed a dark brown-yellow granule distribution in the nuclei of the model group(positive expression). Nerve cell body and dendrites, axons are black or black red,background light yellow. Compared with the model group, the administration group has improved significantly. CONCLUSION OST improves spatial learning and memory of dementia model mice injected with Aβ25-35 in both hippocampus. Experimental studies have shown that OST has different degrees of regulation on neuronal apoptosis, Ca2 +/GLU/oxidative stress and other pathways, and it plays a role in improving multiple AD pathological changes and delaying the pathogenesis of neurodegenerative diseases. 展开更多
关键词 OSTHOLE ALZHEIMER DISEASE AΒ25-35 spatial learning and MEMORY
下载PDF
Adolescent Exposure of JWH-018 “Spice” Produces Subtle Effects on Learning and Memory Performance in Adulthood
14
作者 David M. Compton Megan Seeds +3 位作者 Grant Pottash Brian Gradwohl Chris Welton Ross Davids 《Journal of Behavioral and Brain Science》 2012年第2期146-155,共10页
The active components associated with the bio-designer drugs known variously as “Spice” or “K2” have rapidly gained in popularity among recreational users, forcing the United States Drug Enforcement Administration... The active components associated with the bio-designer drugs known variously as “Spice” or “K2” have rapidly gained in popularity among recreational users, forcing the United States Drug Enforcement Administration to classify these compounds as Schedule I drugs in the Spring of 2011. However, although there is some information about many of the synthetic cannabinoids used in Spice products, little is known about the consequences of the main constituent, (1-pentyl-3-(1-naphthoyl)indole;JWH-018), on neuropsychological development or behavior. In the present experiment, adolescent rats were given repeated injections of either saline or 100 μg/kg of JWH-018. Once the animals were 75 days of age, they were trained using tasks with spatial components of various levels of difficulty and a spatial learning set task. On early trials with water maze tasks of varying difficulty, the JWH-018 treated rats were impaired relative to controls. However, by the end of each phase of testing, drug and control animals were comparable, although on probe trials the drug-treated animals spent significantly less time in the target quadrant. In addition, the performance of the drug-treated rats was inferior to that of the control animals on a learning set task, suggesting some difficulty in adapting their responses to changing task demands. The results suggest that chronic exposure to this potent cannabinoid CB1 receptor agonist during adolescence is capable of producing a variety of subtle changes affecting spatial learning and memory performance in adulthood, well after the drug exposure period. 展开更多
关键词 1-Pentyl-3-(1-naphthoyl)indole JWH-018 K2 SPICE spatial Learning MORRIS Water MAZE Development Memory
下载PDF
NP-14 Effects of Osthole on the Improvement of Learning and Memory Impairment in A Mouse Model Injected with Aβ25-35
15
作者 XU Yuan-bo GAO Qing +3 位作者 FENG Zhao-yang XIAO Yi ZHANG Xiao-Liang HOU Xue-qin 《神经药理学报》 2018年第4期112-113,共2页
Objective:We aimed to investigate the effects of osthole on learning and memory impairment of AD mice induced by injection of Aβ25-35 and the content of Ca2+、GLU、Ab1-42 in the brain tissue and peripheral blood.Meth... Objective:We aimed to investigate the effects of osthole on learning and memory impairment of AD mice induced by injection of Aβ25-35 and the content of Ca2+、GLU、Ab1-42 in the brain tissue and peripheral blood.Methods:Mice were randomly assigned to sham operation,Aβ25-35,Aβ25-35+Ost-L,Aβ25-35+Ost-M,and Aβ25-35+Ost-H group.Water maze test was performed to assessing spatial learning ability of mice.It is determined that the MDA level and the activity of SOD in the brain tissue of mice in each group by colorimetry.The GLU kit and Ca2+kit were used to detect the GLU,Ca2+in tissue and serum.Elisa was used to detect the expression of Aβ1-42 in the hippocampus and serum of mice.HE staining and silver staining were used to detect neuron apoptosis and pathological changes in brain slices.Results:①Effects of osthole on learning and memory:With the increase of training day,the escape latencies continuously reduced in each experimental group,the escape latencies of the model group was longer on the 1st,2nd,3rd,and 5th days than the normal group,the difference was statistically significant(day 3,4:P<0.05,day 5:P<0.01);compared with the model group,the escaping latency on the fifth day of the OST low-medium high-dose group was significantly shortened,which was statistically significant(P<0.05).②Effects on oxidative stresspathway:the SOD activity of AD mice in the hippocampus model group was lower than that in the normal group,which was statistically significant(P<0.05);The SOD activity in the OST group was higher than that in the model group,which was statistically significant(P<0.05).The MDA content in the model group was significantly higher than that in the normal group(P<0.05).The MDA content in the OST high-dose group was lower than that in the model group,which was statistically significant(P<0.05).③Effects of GLU levels on neurotransmitters:the results of the detection of GLU in cortical area and GLU in serum of AD mice in OST dose groups showed that serum GLU levels in the model group were significantly lower than those in the sham group,which was statistically significant(P<0.05).GLU levels in the cortical area were also significantly higher than those in the sham group,which was statistically significant(P<0.05).Compared with the model group,GLU levels in the OST administration group were significantly downregulated.Among the serum,the effect of medium dose group was obvious.Although there was a trend of down-regulation in the cortical administration group,there was no statistical significance.④Changes in Ca2+concentration in the brain;Detection of intracellular Ca ion concentration in AD mice by OST doses showed that,compared with the sham group,the model group was significantly upregulated in cortical Ca2+levels.There was no statistical difference in the administration group.Compared with the model group,the concentration of Ca2+in the OST-H group significantly decreased.⑤Effect on levels of Ab1-42 in hippocampus and serum:model group had significantly higher Ab1-42 levels in hippocampus than in sham operation group,which was statistically significant(P<0.05).Ab1-42 in serum was also significantly upregulated compared to the sham group,which was statistically significant(P<0.05).Compared with the model group,the levels of Aβ1-42 in the OST administration group were significantly down-regulated,with the lower and middle doses in the hippocampus being more significant,while the serum was more pronounced at lower doses.⑥Silver staining to detect the tangles of hippocampal neurons:Neuron tangles in the hippocampal CA1 region showed a dark brown-yellow granule distribution in the nuclei of the model group(positive expression).Nerve cell body and dendrites,axons are black or black red,background light yellow.Compared with the model group,the administration group has improved significantly.Conclusion:OST improves spatial learning and memory of dementia model mice injected with Ab25-35 in both hippocampus.Experimental studies have shown that OST has different degrees of regulation on neuronal apoptosis,Ca2+/GLU/oxidative stress and other pathways,and it plays a role in improving multiple AD pathological changes and delaying the pathogenesis of neurodegenerative diseases. 展开更多
关键词 OSTHOLE Alzheimer’s DISEASE AΒ25-35 spatial learning and MEMORY
下载PDF
区域旅游竞合研究进展 被引量:65
16
作者 史春云 张捷 +1 位作者 沈正平 钟静 《地理与地理信息科学》 CSSCI CSCD 北大核心 2005年第5期85-89,共5页
旅游业的激烈竞争态势使区域旅游空间关系研究成为国内外旅游地理学的研究重点,其中竞争与合作是研究旅游区域之间空间关系最重要的两方面。回顾国内外相关文献,从旅游资源、旅游需求、旅游地形象定位与市场营销、旅游者信息查询行为、... 旅游业的激烈竞争态势使区域旅游空间关系研究成为国内外旅游地理学的研究重点,其中竞争与合作是研究旅游区域之间空间关系最重要的两方面。回顾国内外相关文献,从旅游资源、旅游需求、旅游地形象定位与市场营销、旅游者信息查询行为、知识创新、网络联系与旅游地竞争力、特定旅游目的地的竞争力6方面对区域旅游空间竞争进行综述。目前区域旅游合作研究的热点主要集中在利益主体、企业之间的合作、公共与私有部门的合作以及旅游业与其他关联行业之间的合作等方面。多数研究是单纯对空间竞争或空间合作关系的探讨,而实际上旅游区域之间是竞争与合作并存的空间竞合关系。与近年来区域竞争力、产业竞争力和产业集群等研究热点相比较,国内外关于旅游产业竞争力、旅游区域竞争力和旅游企业集群的研究刚刚起步,对旅游区域之间空间竞合的模式、区域旅游竞合的深层机制和区域旅游空间作用过程的研究则更少,亟待深入探索。 展开更多
关键词 区域旅游 空间竞争 空间合作 空间竞合 研究进展
下载PDF
企业竞合行为的演化博弈试验与集群联盟群体行为研究 被引量:7
17
作者 丁绒 孙延明 《工业技术经济》 CSSCI 北大核心 2013年第4期68-77,共10页
将企业间竞争与合作的微观个体行为与集群联盟的宏观群体行为特征联系起来,探讨两者间的关系。而从该视角定量分析的文献目前鲜为少见。首先依据演化动力产生的根源将集群联盟群体行为分为市场自组织行为和政府控制干预下的行为。接着... 将企业间竞争与合作的微观个体行为与集群联盟的宏观群体行为特征联系起来,探讨两者间的关系。而从该视角定量分析的文献目前鲜为少见。首先依据演化动力产生的根源将集群联盟群体行为分为市场自组织行为和政府控制干预下的行为。接着基于多Agent数值仿真实验的研究方法,通过企业间竞争与合作的重复囚徒困境博弈试验,对集群联盟群体行为的演化进行了深刻的剖析,研究结果表明:在其他条件不变的前提下,不合作者的诱惑得益、企业合作者密度、企业邻域结构、企业空间密度这4个因素与集群联盟群体行为分别呈负向、无、正向、正向相关关系;亦分析了集群联盟群体行为在空间结构上的演化趋势,并且相同的企业往往集中在某几个特定的空间区域,形成团簇,合作者团簇越大,合作伙伴间的关系越稳固。最后在此基础上分别从市场和政府层面给出了具体的对策和建议。 展开更多
关键词 集群联盟 竞合行为 演化博弈 空间结构 群体行为 仿真实验
下载PDF
基于HHT和CSSD的多域融合自适应脑电特征提取方法 被引量:36
18
作者 李明爱 崔燕 +1 位作者 杨金福 郝冬梅 《电子学报》 EI CAS CSCD 北大核心 2013年第12期2479-2486,共8页
为改善运动想象脑电信号特征提取的自适应性和实时性,提出一种基于希尔伯特-黄变换(HHT)与共空域子空间分解算法(CSSD)的特征提取方法(HCSSD).在对脑电信号进行预处理的基础上,定义一种相对距离准则优选脑电极组合;计算脑电的Hilbert瞬... 为改善运动想象脑电信号特征提取的自适应性和实时性,提出一种基于希尔伯特-黄变换(HHT)与共空域子空间分解算法(CSSD)的特征提取方法(HCSSD).在对脑电信号进行预处理的基础上,定义一种相对距离准则优选脑电极组合;计算脑电的Hilbert瞬时能量谱和边际能量谱,以获取脑电的时-频特征,并基于CSSD提取其空域特征,采用串行特征融合策略得到脑电的时-频-空特征;设计学习矢量量化神经网络分类器,实现脑电数据分类.在训练集与测试集间隔一周且减少导联数量的情况下,基于HCSSD对左手小指和舌头的运动想象ECoG脑电数据的平均识别率为92%.实验结果表明:HCSSD在增强特征提取方法的自适应性、改善实时性的同时,提高了脑电信号识别率,为便携式BCI系统在康复领域的应用创造了条件. 展开更多
关键词 脑机接口 运动想象 希尔伯特-黄变换 共空域子空间分解 特征融合 自适应 brain-computer interface (BCI) motor imagery (MI) hilbert-huang transform (HHT) common spatial sub-space decomposition (CSSD )
下载PDF
Influence of Solid Rocket Motor Slag on the Space Debris Environment 被引量:1
19
作者 Bao-Jun Pang Ke-Ke Peng +2 位作者 Wei-Ke Xiao Fang-Fei Ju Dong-Fang Wang 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2013年第6期15-20,共6页
The resulting slag particles from solid rocket motor( SRM) firings are an important component of space debris environment. Slag sizes as large as 1 cm have been witnessed in ground tests,and comparable sizes have been... The resulting slag particles from solid rocket motor( SRM) firings are an important component of space debris environment. Slag sizes as large as 1 cm have been witnessed in ground tests,and comparable sizes have been also estimated via observations of sub-orbital tail-off events. We achieve slag initial data based on MASTER slag model and SRM historical launch data,and propagate slag long-term orbital evolution taking into account the zonal harmonics J2,atmospheric drag,solar radiation pressure and luni-solar attraction to discuss the slag size distribution and orbital characteristics. Finally,future slag debris environment is evaluated based on two different launch rate assumptions. The result shows that current launch frequency will make the slag population sustain growth and the population will not decrease at once even if there are no more launches in the future. 展开更多
关键词 solid rocket motor SLAG space debris orbital distribution spatial densityCLC number:V51 Document code:AArticle ID:1005-9113(2013)06-0015-06
下载PDF
与长途输送和当地污染物排放有关的大气悬浮物中的Cd/Pb和Zn/Pb比例特征(英文)
20
作者 Shih-Chieh Hsu Shaw Chen Liu Ru-Ting Hsu 《干旱区资源与环境》 CSSCI CSCD 2004年第S1期97-103,共7页
Along with windblown dust, large quantities of pollutants are annually brought out of the continental by the westerlies in winter and spring; thereafter they are partly subjected to transport by northeastern monsoon w... Along with windblown dust, large quantities of pollutants are annually brought out of the continental by the westerlies in winter and spring; thereafter they are partly subjected to transport by northeastern monsoon winds to Taiwan. Both PM10 and PM2.5 aerosols collected from northern Taiwan from February 2002 to March 2003 were determined for three heavy metals, namely Pb, Cd and Zn, to characterize the heavy metal compositions between long-range transported and local aerosols and to evaluate their contributions of long-range transport during the northeastern monsoon season. Low Cd/Pb (0.017) and Zn/Pb (1.82) ratios were measured in aerosols during the Asian dust period, in which the sources of ambient aerosols are dominated by long-range transport. By contrast, high Cd/Pb(0.030) and Zn/Pb (3.44) ratios were measured during the summer monsoon season, in which local pollutant emissions dominate the sources of heavy metals. Such characteristic Cd/Pb and Zn/Pb ratios appear to be successfully applied to identify the pollutants originated from the long-range transport or local emissions. 展开更多
关键词 污染物排放 大气悬浮物 Pb和Zn 英文 长途 PM2.5-10 ICP-MS Regression spatial HighC
下载PDF
上一页 1 2 下一页 到第
使用帮助 返回顶部