气候变化和人类活动对洮河流域植被动态的影响研究   总被引：1，自引：0，他引：1  

杨林山  李常斌  王帅兵  杨文瑾 《资源科学》2014,36(9):1941-1948

通过逐象元回归和一致性检验构建1981-2010年间洮河流域NDVI序列,整编同期气温、降水等资料,采用Sen斜率、主成分、相关性及回归残差分析等方法,就洮河流域不同地理-生态区间植被动态的时空特征及所受气候变化和人类活动的影响进行研究。结果表明,1981-2010年期间,洮河流域植被动态总体增强且空间分异明显,甘南高原植被动态增强幅度高于黄土区。从植被季节变化的趋势和幅度来看,甘南高原主要表现为植被萌发期提前,黄土区表现为萌发期提前和枯萎期延迟。在气温和降水所代表的水热要素与NDVI之间构建植被动态预测模式,率定和校验期精度良好,能够反映不同生态-地理区间植被动态与气候变化之间的数量关系。总体来看,洮河流域植被变化由气候和人类活动共同驱动,气候模式输出和残差分析结果表明,洮河流域植被动态受气候因素的影响显著,气候变化对洮河流域植被活动增强的贡献率超过90%。  相似文献   

Understanding information diffusion with psychological field dynamic     

《Information processing & management》2022,59(4):102956

Several approaches focus on how to automatically capture the latent features from original diffusion data and predict the future scale of cascades utilizing a black box framework. However, they ignore the penetrating insight into the underlying mechanism that how each participant is involved in the cascade. In this work, we bridge the gap between prediction and understanding of information diffusion by incorporating deep learning techniques and social psychology. To characterize individual participation driven by both subjective and objective impetus and integrate it into the macro-level cascade, we propose an end-to-end model, named PFDID, which is designed based on the field dynamics theory of psychology, including the intrinsic cognition field and the extrinsic environment field. We represent these two field dynamics respectively with the pairwise semantic relation between the message itself and corresponding comment and the forwarder’s micro-community activity embedding to provide educated explanations for forwarding behaviour. Afterwards, the cross infusion mechanism is designed to calculate the mutual influence of inhomogeneous field dynamics inside users and cross influence of homogeneous field dynamics among individuals, whose output is fed into the diffusion network aggregation layer for the cascade size prediction. Extensive experiments on two typical social networks, Sina Weibo and Twitter, manifest that the proposed PFDID outperforms state-of-the-art approaches. Our model achieves excellent prediction results, with MSLE = 1.856 on Sina Weibo and MSLE = 1.962 on Twitter, providing 6.54% and 10.53% relative performance gains, respectively. Furthermore, the interpretability is also discussed based on detailed visualization. We observe that the psychological impetus behind social behaviour varies mainly following two patterns with the spread of information, including gradual change and joint influence. Additionally, the indirect dependencies have also been verified.  相似文献   

科研人员视角下科学数据安全影响因素仿真分析     

阮冰颖  刘桂锋  刘琼 《情报理论与实践》2022,(2)

[目的/意义]科学数据已经成为科学研究的重要资源,科研人员面临保护科学数据安全的新挑战。[方法/过程]第一步,从政策、资金、设备、平台、科学数据价值、科研人员专业素养的角度设计问卷;第二步,基于问卷回收数据构建SEM模型;第三步,构建SD模型并对6个维度变化进行动态仿真,探究科学数据安全系统中各因素之间的相互作用关系。[结果/结论]政策、资金、设备、平台、科学数据价值、科研人员专业素养对科学数据安全具有影响,其中政策、平台、科学数据价值对科学数据安全的作用较明显。[局限]考虑的科学安全影响因素尚不全面,还需要进一步优化SD模型。  相似文献   

政府数据开放的知识创造机理研究     

袁莉  徐丽新  姚乐野 《情报理论与实践》2022,(2):78-84

[目的/意义]探明政府数据开放(Open Government Data, OGD)知识创造机理有助于推动其价值实现。[过程/方法]基于创造力成分模型识别出OGD知识创造主体、过程活动及影响因素,构建OGD知识创造机理模型;进一步构造OGD知识创造系统动力学模型,通过仿真与模拟探究OGD知识创造活动与影响因素间的复杂关系及动态变化规律。[结果/结论]OGD知识创造包括两类主体、5个阶段活动以及4类影响因素(11个具体要素),各影响因素及具体要素通过不同路径作用于OGD知识创造,并由此提出OGD知识创造的发展建议。  相似文献   

基于大数据思维的小微企业竞争情报预警机制仿真研究     

王克平  王艺  车尧 《情报理论与实践》2022,(2):103-110

[目的/意义]从大数据思维视角入手探究小微企业竞争情报预警机制的构建及其仿真效果,为小微企业顺利开展竞争情报预警工作提供借鉴。[方法/过程]以小微企业为研究对象,探究基于大数据思维的小微企业竞争情报预警机制,运用系统动力学方法构建了预警机制间各要素的因果反馈关系图与系统流图,利用Vensim PLE软件进行模型仿真模拟。[结果/结论]由仿真结果可知,模型很好地模拟了小微企业竞争情报预警机制的运作,灵敏度分析揭示了大数据技术应用率、企业战略联盟参与率、风险指标体系参照率、竞争情报方法应用率、制度完善程度都对竞争情报预警有正向影响,可为小微企业开展竞争情报预警工作提供理论依据和决策支持。  相似文献   

碳达峰目标下中国绿色建造技术驱动因素的作用机制：基于系统动力学仿真分析     

孙国帅  姜德龙  冯娇  陈行行 《科技管理研究》2022,(14)

绿色建造技术的推广与应用是促进建筑业持续健康发展的根本路径之一,为有效解决目前我国绿色建造技术推广与应用遇到的障碍,在研究国内外相关主要研究成果的基础上,总结归纳影响绿色建造技术发展的因素,并从市场、经济、生态以及社会参与度等角度得到关键驱动因素,据此构建系统动力学仿真模型,对有关驱动因素进行灵敏度的动态分析并观察各主要因素的影响效果,得到碳达峰目标下我国绿色建造技术驱动因素的作用机制。结果表明：各驱动因素对我国绿色建造技术的推广与应用具有正向的促进作用,但影响程度不同,技术研发程度、政策法律完善程度、绿色建造管理模式、节水节地技术效率对成本影响明显,而对生态价值和生产力效率影响不同。根据研究结论,从绿色建造政策法规、技术研发、管理模式和技术效率等方面提出相关对策建议。  相似文献   

基于CAS理论我国生物医药产业创新集群演化动力机制研究     

李洁  葛燕飞  高丽娜 《科技管理研究》2022,(3)

研究我国生物医药产业创新集群演化动力机制,为促进我国生物医药产业创新能力提升提供决策依据。运用复杂适应系统理论模型,分析生物医药创新集群的聚集、非线性、流、多样性特征与标识机制、内部模型机制和积木机制。在此基础上建立生物医药创新集群演化机制的回声模型,运用不完全信息下的重复静态博弈分析主体互动作用,并运用涌现模型分析系统涌现机制。生物医药产业创新集群是复杂适应系统,具备其所有特征;创新集群主体通过流空间网络实现交互学习并适应性调整自身行为;通过交互学习,创新集群主体产生了与其他主体合作创新的可能性,但是否真正实现合作创新取决于主体间竞争合作博弈的结果;涌现推动生物医药产业创新集群演化发展。涌现包括知识涌现和创新网络的涌现,通过涌现创新集群产生新的更优的系统功能和结构,可实现生物医药产业创新集群的可持续发展。  相似文献   

Lower extremity power during the squat jump with various barbell loads     

Daniel Jandacka  Jaroslav Uchytil  Roman Farana  David Zahradnik  Joseph Hamill 《Sports biomechanics / International Society of Biomechanics in Sports》2014,13(1):75-86

The purpose of this study was twofold: (1) to determine the barbell load that maximised the system power as well as the ankle, knee, and hip joint powers during the squat jump, and (2) to compare the system powers computed from two different methods: the centre of mass (COM) method and the barbell method. Seven male throwers were recruited in this study. The system power (COM method) and the ankle, knee, and hip joint powers were determined with the load incrementally set at 0%, 10%, 30%, 50%, 70%, and 90% of one repetition maximum. The largest system power was observed at the load of 30% (p < 0.008) while the largest ankle and knee powers were observed at 70% and 0% (p < 0.05). The barbell method overestimated the system power (p < 0.001) when compared to the COM method. It was concluded that the barbell method could influence load optimisation in squat jump. The optimal barbell load which maximised the system power did not maximise the ankle, knee, or hip power simultaneously.  相似文献   

Unsteady flow phenomena in human undulatory swimming: a numerical approach     

Steffen Pacholak  Stefan Hochstein  Alexander Rudert  Christoph Brücker 《Sports biomechanics / International Society of Biomechanics in Sports》2014,13(2):176-194

The undulatory underwater sequence is one of the most important phases in competitive swimming. An understanding of the recurrent vortex dynamics around the human body and their generation could therefore be used to improve swimming techniques. In order to produce a dynamic model, we applied human joint kinematics to three-dimensional (3D) body scans of a female swimmer. The flow around this dynamic model was then calculated using computational fluid dynamics with the aid of moving 3D meshes. Evaluation of the numerical results delivered by the various motion cycles identified characteristic vortex structures for each of the cycles, which exhibited increasing intensity and drag influence. At maximum thrust, drag forces appear to be 12 times higher than those of a passive gliding swimmer. As far as we know, this is the first disclosure of vortex rings merging into vortex tubes in the wake after vortex recapturing. All unsteady structures were visualized using a modified Q-criterion also incorporated into our methods. At the very least, our approach is likely to be suited to further studies examining swimmers engaging in undulatory swimming during training or competition.  相似文献   

Comparison of support leg kinetics between side-step and cross-step cutting techniques     

Yuta Suzuki  Michiyoshi Ae  Shunsuke Takenaka  Norihisa Fujii 《Sports biomechanics / International Society of Biomechanics in Sports》2014,13(2):144-153

The purpose of this study was to investigate differences in the support leg joint moment and moment power between side-step (SS) and cross-step (CS) cutting techniques with a prescribed 90° cutting angle. Ground reaction forces (1,000 Hz) and three-dimensional kinematics (250 Hz) of SS and CS cutting techniques were collected from 20 male college athletes. Normalised peak knee extension moment was larger in the SS technique than in the CS technique (0.40 ± 0.10 in SS; 0.26 ± 0.08 in CS). In the SS technique, the knee extensors ( ? 0.10 ± 0.06 in SS; ? 0.02 ± 0.04 in CS) and ankle plantarflexors ( ? 0.12 ± 0.05 in SS; ? 0.07 ± 0.03 in CS) did significantly more negative work (normalised). The direction change angle (40.5 ± 8.7° in SS; 33.0 ± 6.8° in CS) and the decrease in horizontal velocity of the centre of mass ( ? 0.63 ± 0.23 m/s in SS; ? 0.31 ± 0.23 m/s in CS) were significantly larger in the SS technique. These results suggest that the SS technique is an effective means of changing running direction at the expense of velocity of the centre of mass and that the CS technique is better for minimising the reduction in horizontal velocity of the centre of mass.  相似文献