北京地区8种园林树木的叶片和枝条重金属含量比较

为了解不同园林树木重金属的吸收情况，以北京市陶然亭公园、中科院植物园、紫竹院公园、马甸公园、皇城根遗址公园和营城建都滨水绿道为样地，采用ICP光谱仪测定了8种园林树木叶片、一年生枝条以及相应土壤中重金属Cd、Pb、Cu的含量，并对叶片与一年生枝条中重金属含量以及树木与土壤重金属含量进行了相关性分析。结果表明，不同树种重金属含量有显著差异且因重金属种类而异；叶片和枝条中Cd含量排序为：紫薇＞金银木＞太平花＞锦带＞珍珠梅＞紫丁香＞木槿＞砂地柏，Pb含量排序为：锦带＞木槿＞太平花＞金银木＞紫丁香＞紫薇＞砂地柏＞珍珠梅，Cu含量排序为：金银木＞紫薇＞紫丁香＞珍珠梅＞木槿＞太平花＞锦带＞砂地柏；树木不同器官中重金属含量也不同，叶片与枝条中Pb含量具有显著相关性；树木叶片和一年生枝条的Cd、Pb、Cu重金属既来源于土壤，也来源于大气污染。8种园林树木中，对Cd、Pb、Cu吸收量最大的分别是紫薇、锦带和金银木；紫薇和金银木同时对Cd和Cu、太平花同时对Cd和Pb有较强的吸收力，而砂地柏吸收力较弱。本研究对园林绿地选择富集重金属能力强的树种有参考价值。     

Predicting the failures of prediction markets: A procedure of decision making using classification models

Prediction markets have been an important source of information for decision makers due to their high ex post accuracies. Nevertheless, recent failures of prediction markets remind us of the importance of ex ante assessments of their prediction accuracy. This paper proposes a systematic procedure for decision makers to acquire prediction models which may be used to predict the correctness of winner-take-all markets. We commence with a set of classification models and generate combined models following various rules. We also create artificial records in the training datasets to overcome the imbalanced data issue in classification problems. These models are then empirically trained and tested with a large dataset to see which may best be used to predict the failures of prediction markets. We find that no model can universally outperform others in terms of different performance measures. Despite this, we clearly demonstrate a result of capable models for decision makers based on different decision goals.     

Data mining in road crash analysis: the context of developing countries

The recent advancements in the field of data mining have made vast progress in extracting new information and hidden patterns from large datasets which are often overlooked by the traditional statistical approaches. These methods focus on searching for new and interesting hypothesis which were previously unobserved. Road safety researchers working with the crash data from developed world have seen encouraging success in obtaining new insight into crash mechanism through data mining. An attempt was made in this study to apply these advance methods and evaluate their performance in manifesting crash causes for Bangladesh. The study applies hierarchical clustering to identify hazardous clusters, random forest to find important variables explaining each of these clusters, and classification and regression trees to unveil their respective crash mechanisms for the road crash data of Bangladesh. The results identified several new interesting relationships and acknowledged issues related to quality of data.     

Predictability and interpretability of hybrid link-level crash frequency models for urban arterials compared to cluster-based and general negative binomial regression models

Machine learning (ML) techniques have higher prediction accuracy compared to conventional statistical methods for crash frequency modelling. However, their black-box nature limits the interpretability. The objective of this research is to combine both ML and statistical methods to develop hybrid link-level crash frequency models with high predictability and interpretability. For this purpose, M5′ model trees method (M5′) is introduced and applied to classify the crash data and then calibrate a model for each homogenous class. The data for 1134 and 345 randomly selected links on urban arterials in the city of Charlotte, North Carolina was used to develop and validate models, respectively. The outputs from the hybrid approach are compared with the outputs from cluster-based negative binomial regression (NBR) and general NBR models. Findings indicate that M5' has high predictability and is very reliable to interpret the role of different attributes on crash frequency compared to other developed models.     

浙江丽水药用观赏蕨类植物资源调查研究

研究了丽水药用观赏蕨类植物30科43属59种的植物种类、生境、药用观赏部位及功能,并分析了开发利用价值及前景。     

Understanding travel expenditure by means of market segmentation

Consolidated tourism destinations should expand their market share by focusing on tourism spending instead of number of travellers. This strategy emphasises satisfying the preferences and needs of tourists more dynamically in terms of their expenditure patterns. The purpose of this paper consists of evaluating the usefulness of an expenditure-based segmentation as a relevant instrument of tourism policy in order to increase the economic benefits from travellers to Andalusia. More specifically, by means of decision trees and linear regression statistical techniques, heavy spenders are identified as well as exploring which variables might be considered as the best predictors of travel expenditure. Finally, the implications of the results are discussed, as they may provide practical guidance for tourism practitioners at similar destinations.     

九阜山观赏蕨类植物资源及其开发利用

为合理开发与利用观赏蕨类植物资源,对福建省尤溪县九阜山省级自然保护区的观赏蕨类植物资源进行调查,发现具有观赏价值的野生蕨类植物共有33科53属87种;对该区各种观赏蕨按观赏用途进行分类,对其种类组成、垂直分布、水平与生态分布、优势资源以及利用途径进行分析,并提出保护与开发利用建议。     

商洛市行道树选择的探讨

在了解城市行道树选择原则的基础上,以商洛市行道树种为例进行分析,同时对树种的选择进行探讨,并提出了改善商洛市行道树树种的建议。     

Incorporating real-options analysis into the accounting curriculum

In this paper, we argue that accounting curricula should be expanded to cover the topic of real options. Our argument relies on reference to the [American Institute of Certified Public Accountants (AICPA) (1999) (Core Competency Framework, New York, NY: AICPA <http://ceae.aicpa.org/Resources/Education+and+Curriculum+Development/Core+Competency+Framework+and+Educational+Competency+Assessment+Web+Site/> Accessed 21.08.08], the framework for curriculum change espoused by [Arya, A., Fellingham, J. C., & Schroeder, D. A. (2003). An academic curriculum proposal. Issues in Accounting Education, 18(1) 29–35], a global study of core competencies for management accountants [International Federation of Accountants (IFAC), (2002). Competency profiles for management accounting practice and practitioners. New York, NY: International Federation of Accountants], a global capital-budgeting “best practices statement” [International Federation of Accountants (IFAC), (2008). International good practice guidance: Project appraisal using discounted cash flow. New York, NY: International Federation of Accountants], current specifications of the CMA exam [Institute of Management Accountants (IMA), (2008). Certified management accountant (CMA) learning outcome statements (effective 07/01/04), updated 07/2008. <http://www.imanet.org/pdf/CMA%20%20LOS.pdf> Accessed 29.10.08.], and elements of the Albrecht and Sack report [Albrecht, W. S., & Sack, R. J. (2000). Accounting education: Charting the course through a perilous future. Accounting education series, Vol. 16. Sarasota, FL: American Accounting Association]. We make special reference to the linkage of the topic of real options to two broad educational goals: decision-modeling and risk analysis. Existing resources that accounting faculty can use to incorporate real options into the curriculum are limited. As a response, we provide an extended example that accounting educators can use to cover the topic of real options. This example uses a set of binomial trees (one for cash inflows and another for cash outflows). The step-by-step approach presented in this paper allows students without a technical/mathematical background to extend discounted-cash-flow (DCF) decision models (e.g., NPV) to incorporate real options that are embedded in proposed investment projects.     

植物矮化激素对茶条槭生长及观赏性作用的研究

利用不同植物矮化激素对茶条槭进行喷施试验。结果表明,不同激素对茶条槭的生长效果及观赏性有明显的作用;对茶条槭矮化效果最佳的是10ml/L的国光矮壮素和浓度为2g/L的国光多效唑。