黑龙江省垂直绿化攀缘树种的筛选

在分析垂直绿化植物生长主要限制因子--土壤干旱与贫瘠的基础上,从黑龙江省山地植被中引种栽培19种攀援树种,对其生物学特性、生活习性、抗旱性等关键因素进行了试验研究。根据试验及露地栽培观察结果,采用"百分法"综合评价出17种适宜立体绿化的攀援树种,为立体绿化与植被恢复提供了更多可供参考的植物种类,以满足绿化中对景观多样性、植物多样性的要求。     

四川退耕农户自我发展模式及启示

四川退耕还林工程自1999年启动以来,取得了显著的生态效益和社会经济效益。文章通过对四川退耕还林典型地区的调查,总结出两类主要的退耕农户自我发展模式,并对其优点和存在的问题进行了分析,最后从寻找适合农户自我发展模式,保障农户长远发展和巩固退耕还林成果的角度,总结了许多有益的经验和启示。     

林木损失额价值计量及损毁程度系数研究——以北京地区为例

提出林木损失额的价值计量以损毁程度系数(Kd)作为调整值,并且对树木的生理损毁、观赏损毁、生理和观赏部位同时损毁三种受损类型分别进行讨论,提出根据树木损毁程度(d)与价值损失之间的强度系数(ε)来确定损毁程度系数的方法。根据损毁程度系数计算公式Kd=dε,计算得出不同损毁程度下树木生理损毁程度系数值。其意义在于解决了由于林木损伤程度的不同,而体现出林木价值损失额的不同,从而为更加准确、合理地计量林木损失额提供了科学依据。     

Finding Closest Targets in Non-Oriented DEA Models: The Case of Convex and Non-Convex Technologies

This paper draws attention for the fact that traditional Data Envelopment Analysis (DEA) models do not provide the closest possible targets (or peers) to inefficient units, and presents a procedure to obtain such targets.It focuses on non-oriented efficiency measures (which assume that production units are able to control, and thus change, inputs and outputs simultaneously) both measured in relation to a Free Disposal Hull (FDH) technology and in relation to a convex technology. The approaches developed for finding close targets are applied to a sample of Portuguese bank branches.     

Achieving smooth asymptotics for the prices of European options in binomial trees

A new binomial approximation to the Black–Scholes model is introduced. It is shown that, for digital options and vanilla European call and put options, a complete asymptotic expansion of the error in powers of n ^?1 exists. This is the first binomial tree for which an asymptotic expansion has been shown to exist.     

湿陷性黄土地区城市绿化与地基变形的关系研究

湿陷性黄土地区绿化带需灌溉,如果灌溉水量过大将会导致湿陷性土层的含水量增大,当含水量增大至湿陷起始含水量时,湿陷性土层开始产生湿陷现象。为了防止湿陷性黄土地区因大量灌溉水进入土中,导致湿陷,本文根据湿陷性土层的湿陷机理及湿陷性黄土的本构关系,提出湿陷性土层上绿化区域防止湿陷的具体方法。     

邯郸市主城区主要行道树的多样性调查分析

本项研究采用抽样调查方法对邯郸市主城区20条主要道路的行道树进行的详细调查,分析邯郸市主城区行道树的物种组成、胸径,探讨多样性指数和行道树绿化发展趋势。结果表明:①邯郸市主城区行道树共有18科25属28种,其中乔木20种,隶属19属14科;行道树种类最多的科是蔷薇科,悬铃木(Platanus hispanica)、国槐(Sophora japonica linn)、紫薇(Lagerstroemia indica)、毛白杨(Populus tomentosa Carr)、栾树(Koelreuteria paniclata Laxm)、银杏(Ginkgo biloba)、臭椿(Ailanthus altissima)、美国白蜡(Fraxinus americana)是邯郸市主城区行道树的骨干树种。②针对邯郸市行道树多样性的不足,提出了邯郸市行道树绿化的发展趋势。     

A safe speed guidance model for highways

ABSTRACT

This paper presents a fuzzy logic model to support decisions for the suggested speed limit for sections of highways as they become affected by adverse road conditions, environmental factors and differing traffic levels. The definition of the main factors, and their weight, that reduce safety on highways was conducted by the Delphi method, consulting traffic engineering experts. The survey served as a basis for structuring indicators and indexes in a soft decision tree, structured by a fuzzy logic system. The system can be used to support the decisions of those that manage the roads, indicating to drivers’ speeds, by visual, audible or combined systems.     

Olive oil production and soil conservation in southern Spain, in relation to EU subsidy policies

The European Union spent about two billion ECU per year on subsidies for the olive oil sector, of which Spain received about 35%. For the rainfed areas in southern Spain the olive oil sector is crucial, and so are these subsidies. The European Commission has formulated two options to change the subsidy system, but these do not take the production systems and environmental aspects into account. Many olive plantations are affected by soil erosion. This paper analyses the olive tree production systems in southern Spain, the subsidy systems and the soil erosion problems. It then raises the question whether the subsidies could not be provided in a different way, in order to make olive tree cultivation more sustainable by reducing soil erosion and flood hazard.