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This paper reports on the forms of reasoning elicited as fourth grade students in a suburban district and sixth grade students in an urban district worked on similar tasks involving reasoning with the use of Cuisenaire rods. Analysis of the two data sets shows similarities in the reasoning used by both groups of students on specific tasks, and the tendency of a particular task to elicit numerous forms of reasoning in both groups of students. Attributes of that task and ways that those attributes can be replicated in other domains may have implications in the teaching of early reasoning.  相似文献   
33.
This paper explores a statistical mechanics approach as a means to better understand specific land cover changes on a continental scale. Integrated assessment models are used to calculate the impact of anthropogenic emissions via the coupling of technoeconomic and earth/atmospheric system models and they have often overlooked or oversimplified the evolution of land cover change. Different time scales and the uncertainties inherent in long term projections of land cover make their coupling to integrated assessment models difficult. The mainstream approach to land cover modelling is rule-based methodology and this necessarily implies that decision mechanisms are often removed from the physical geospatial realities, therefore a number of questions remain: How much of the predictive power of land cover change can be linked to the physical situation as opposed to social and policy realities? Can land cover change be understood using a statistical approach that includes only economic drivers and the availability of resources? In this paper, we use an energy transition paradigm as a means to predict this change. A cost function is applied to developed land covers for urban and agricultural areas. The counting of area is addressed using specific examples of a Pólya process involving Maxwell–Boltzmann and Bose–Einstein statistics. We apply an iterative counting method and compare the simulated statistics with fractional land cover data with a multi-national database. An energy level paradigm is used as a basis in a flow model for land cover change. The model is compared with tabulated land cover change in Europe for the period 1990–2000. The model post-predicts changes for each nation. When strong extraneous factors are absent, the model shows promise in reproducing data and can provide a means to test hypothesis for the standard rules-based algorithms.  相似文献   
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—本文设计了实现车载GPS/DR组合导航系统最优综合的联合卡尔曼滤波器,并给出了滤波算法。提出了一种自适应联合卡尔曼滤波器结构及其算法,并应用于GPS/DR组合导航系统的最优综合校正中。理论分析及计算机仿真结果均表明,应用该自适应联合卡尔曼滤波器可大大提高车载GPS/DR组合导航系统的定位精度及容错能力。  相似文献   
35.
建设用地的扩张对我国非农经济增长贡献研究   总被引:3,自引:0,他引:3  
土地要素对经济增长的贡献,由于其供给缺乏弹性而常被定量研究所忽略。文章通过分析土地要素对经济增长的作用,提出在定量研究土地要素的贡献时,应使用代表土地承载空间大小的建筑面积数据。文章构建了相对建筑面积估计模型,并使用资本和劳动力数据实际估算了我国建设用地相对建筑的面积,并利用超越对数生产函数形式实际估算了我国建设用地对非农经济增长的贡献。研究发现:我国28个省级单位建设用地面积扩大在2003-2008年对非农经济增长平均贡献率为2.88%,而代表土地利用强度的相对容积率的增长对经济增长的贡献率为8.79%。建设用地对非农经济增长的总贡献为11.81%。  相似文献   
36.
We show that a hierarchical cities structure can be generated by a self-organized process which grows with a bottom-up mechanism, and that the resulting distribution is power law. First we analytically prove that the power law distribution satisfies the balance between the offer of the city and the demand of its basin of attraction, and that the exponent in the Zipf's law corresponds to the multiplier linking the population of the central city to the population of its basin of attraction. Moreover, the corresponding hierarchical structure shows a variable spanning factor, and the population of the cities linked to the same city up in the hierarchy is variable as well. Second a stochastic dynamic spatial model is proposed, whose numerical results confirm the analytical findings. In this model, inhabitants minimize the transportation cost, so that the greater the importance of this cost, the more stable is the system in its microscopic aspect. After a comparison with the existent methods for the generation of a power law distribution, conclusions are drawn on the connection of hierarchical structure, and power law distribution, with the functioning of the system of cities.  相似文献   
37.
Heracleum sphondylium L. subsp. ternatum (Velen.) Brummitt. commonly known as “hogweed” is traditionally used to manage several human ailments. This investigation assessed, for the first time, the enzyme inhibitory properties, antioxidant activity, phytochemical profile, antimutagenic, and antimicrobial potential of the ethyl acetate, methanol, and water extracts of H. sphondylium. We also established the possible interactions of identified phenolic compounds with cholinesterases, amylase, glucosidase, and tyrosinase using in silico docking studies. Chlorogenic acid was found in high amounts in the methanol extract of H. sphondylium. The methanol extract was an effective inhibitor of acetylcholinesterase (1.70 mg galantamine equivalent (GALAE)/g extract) while the ethyl acetate extract showed pronounced inhibitory action against butyrylcholinesterase (1.77 mg GALAE/g extract). The extracts exhibited low inhibition against amylase (0.12-0.84 mmol acarbose equivalent (ACAE)/g extract) and a more pronounced inhibition against glucosidase (2.29–3.65 mmol ACAE/g extract). In silico results showed that rutin and quercetin (-70.4 and -72.2 Kcal/mol, for rutin and quercetin respectively) docked to the enzymatic cavity of acetylcholinesterase but these phenolic compounds showed less affinity with butyrylcholinesterase (-15.0 and -5.2 Kcal/mol, for rutin and quercetin respectively). The extracts did not induce any mutations on the bacterial strains, while they have excellent antimutagenic capacity against well-known mutagens (inhibition values 98%, 97% and 96%). The methanol extract (0.78 mg/ml) showed moderate antifungal activity while the ethyl acetate extract (0.78–3.12 mg/ml) showed weak to moderate antimicrobial activity. This study provides valuable baseline data which might serve for the development of future pharmacophores for the management of human ailments.  相似文献   
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土地利用信息是国土资源管理的基础和重要依据,随着高分辨率遥感图像数据的日益增多,迫切需要快速准确的土地利用分类方法。目前应用较广的面向对象的分类方法对空间特征的利用尚不够充分,在特征选择上存在一定的局限性。为此,提出一种基于多尺度学习与深度卷积神经网络(deep convolutional neural network,DCNN)的多尺度神经网络(multi-scale neural network,MSNet)模型,基于残差网络构建了100层编码网络,通过并行输入实现输入图像的多尺度学习,利用膨胀卷积实现特征图像的多尺度学习,设计了一种端到端的分类网络。以浙江省0.5 m分辨率的光学航空遥感图像为数据源进行了实验,总体分类精度达91.97%,并将其与传统全卷积网络(fully convolutional networks,FCN)方法和基于支持向量机(support vector machine,SVM)的面向对象方法进行了对比,结果表明,本文所提方法分类精度更高,分类结果整体性更强。  相似文献   
40.
Ageratum conyzoides L. (Family—Asteraceae) is an annual aromatic invasive herb, mainly distributed over the tropical and subtropical regions of the world. It owns a reputed history of indigenous remedial uses, including as a wound dressing, an antimicrobial, and mouthwash as well as in treatment of dysentery, diarrhea, skin diseases, etc. In this review, the core idea is to present the antifungal potential of the selected medicinal plant and its secondary metabolites against different fungal pathogens. Additionally, toxicological studies (safety profile) conducted on the amazing plant A. conyzoides L. are discussed for the possible clinical development of this medicinal herb. Articles available from 2000 to 2020 were reviewed in detail to exhibit recent appraisals of the antifungal properties of A. conyzoides. Efforts were aimed at delivering evidences for the medicinal application of A. conyzoides by using globally recognized scientific search engines and databases so that an efficient approach for filling the lacunae in the research and development of antifungal drugs can be adopted. After analyzing the literature, it can be reported that the selected medicinal plant effectively suppressed the growth of numerous fungal species, such as Aspergillus, Alternaria, Candida, Fusarium, Phytophthora, and Pythium, owing to the presence of various secondary metabolites, particularly chromenes, terpenoids, flavonoids and coumarins. The possible mechanism of action of different secondary metabolites of the plant against fungal pathogens is also discussed briefly. However, it was found that only a few studies have been performed to demonstrate the plant’s dosage and safety profile in humans. Considered all together, A. conyzoides extract and its constituents may act as a promising biosource for the development of effective antifungal formulations for clinical use. However, in order to establish safety and efficacy, additional scientific research is required to explore chronic toxicological effects of ageratum, to determine the probability of interactions when used with different herbs, and to identify safe dosage. The particulars presented here not only bridge this gap but also furnish future research strategies for the investigators in microbiology, ethno-pharmacology, and drug discovery.  相似文献   
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