Microecosystem Analysis of the Structure and Functions of Forest Biogeocenoses

The microecosystem approach and an adequate system of quantitative methods have been used to study the relationship between the chorologic changes in the structure and functions of edificator tree stand and other components of the pine (Pinus sylvestris L.) forest cenoecosystems of the Transural and Northern Turgai regions. Significant correlations of the density of pine undergrowth with the litter thickness; of its growth with root competition, stand closeness, and, to a lower degree, photosynthetically active radiation (PAR); and of the numbers of small mammals and groups of soil mesofauna with herbaceous phytomass have been found. The possibility of the synthesis of population-ecological, synecological, and biogeocenological methods has been demonstrated.     

EVAPOTRANSPIRATION AND CANOPY RESISTANCE AT AN UNDEVELOPED PRAIRIE IN A HUMID SUBTROPICAL CLIMATE1

ABSTRACT: Reliable estimates of evapotranspiration from areas of wildland vegetation are needed for many types of water-resource investigations. However, little is known about surface fluxes from many areally important vegetation types, and relatively few comparisons have been made to examine how well evapotranspiration models can predict evapotranspiration for soil-, climate-, or vegetation-types that differ from those under which the models have been calibrated. In this investigation at a prairie site in west-central Florida, latent heat flux (λE) computed from the energy balance and alternatively by eddy covariance during a 15-month period differed by 4 percent and 7 percent on hourly and daily time scales, respectively. Annual evapotranspiration computed from the energy balance and by eddy covariance were 978 and 944 mm, respectively. An hourly Penman-Monteith (PM) evapotranspiration model with stomatal control predicated on water-vapor-pressure deficit at canopy level, incoming solar radiation intensity, and soil water deficit was developed and calibrated using surface fluxes from eddy covariance. Model-predicted λE agreed closely with λE computed from the energy balance except when moisture from dew or precipitation covered vegetation surfaces. Finally, an hourly PM model developed for an Amazonian pasture predicted λE for the Florida prairie with unexpected reliability. Additional comparisons of PM-type models that have been developed for differing types of short vegetation could aid in assessing interchangeability of such models.     

Physical Modelling of Urban Roughness using Arrays of Regular Roughness Elements

The aerodynamic behaviour of large urbanagglomerations must be represented in increasingly greaterdetail, as large-scale numerical weather prediction and airpollution dispersion models are refined. The present studyprovides detailed measurements of the flow field in regulararrays of obstacles to obtain representative data on meanflow and turbulence statistics in urban-type areas. Obstacle arrays consisting of simple cubes and flat plateroughness commonly used in boundary layer simulations wereplaced in a simulated atmospheric boundary layer flow in ahydraulic flume. The scale factor was about 1:200 based onthe obstacle height (50 mm). The results show noappreciable `constant stress' region in the internalboundary layer above the buildings, since in any finite-length test array the boundary layer is always developing.However, if the RMS turbulence components are scaled by thelocal values of the shear stress, then there seems to be auniversal scaling, with _u/u_* = 2.1,_v/u_* = 1.65 and _w/u_* = 1.2. This greatly simplifies the parameterization of the first orderturbulence statistics in obstacle arrays. It was alsoobserved during the experiments that, compared to results inthe cube arrays, the turbulence kinetic energy and theReynolds stresses were almost doubled in the flat plateroughness arrays.     

Comparison of Four Machine Learning Methods for Predicting PM10 Concentrations in Helsinki, Finland

Machine learning methods can offer a practicalalternative to deterministic and statistical methods forpredicting air pollution concentrations. However, for agiven data set, it is often not clear beforehand whichmachine learning method will yield the best predictionperformance. This study compares the variable selection andprediction performance of four machine-learning methods ofdifferent complexity: logistic regression, decision tree,multivariate adaptive regression splines and neuralnetwork. The methods are applied to the task of predictingthe exceedance of the European PM₁₀ daily averageobjective of 50 g m^-3 for a station in Helsinki,Finland. Our study shows that some predictors were selectedby all models but that the different models also pickeddifferent variables. The performance of three of the fourmethods investigated was very similar, however, performanceof the decision tree method was significantly inferior.Performance was sensitive to the learning sample size andtime period used.     

Urban waste recycling behavior: antecedents of participation in a selective collection program

ABSTRACT/ The aim of this study is to analyze the antecedents of urban waste recycling behavior. To achieve this goal, a concrete urban waste management program was chosen. The study focuses on the Selective Collection Program (SCP) in Zaragoza, a medium-sized city in northeastern Spain. The research starts with a conceptual model in which the variables that potentially affect recycling behavior can be classified into two groups: incentives and barriers. Moreover, the sociodemographic characteristics of the individuals are included in our study. Given that the proposed model requires specification of latent variables or constructs, the analysis is based on the Structural Equation Models (SEM) methodology. The results revealed that environmental awareness, knowledge of the environmental impact of urban waste, and the positive perception of management by local government exercise a positive effect on individual recycling behavior, while perceived personal difficulties (space and time availability) and distance to and from the container have a negative effect. As regards sociodemographic variables, this study found that annual family income sustains a negative relationship with recycling behavior, while age maintains a positive one. The results obtained clearly show the important role that the public authorities play, especially municipal governments, in achieving the waste recycling objectives established in accordance with international legislation.     

Measurement and Modelling of Ammonia Emissions at Waste Treatment Lagoon-Atmospheric Interface

Global emissions of ammonia are approximately 75 Tg N/yr (1 Tg =10¹²g). The major global source is excreta from domestic animals ( 32 Tg N ^-1yr^-1). Waste storage and treatment lagoonsare used to treat the excreta of hogs in North Carolina (NC). Proteins and nitrogen rich compounds in the lagoon are convertedto ammonia, through a series of biological and chemical transformations. The process of ammonia emission has been investigated using two different model approaches: (1) CoupledMass Transfer with Chemical Reaction Model (Model I), and (2)Mass Transport without Chemical Reaction Model (Model II). Asensitivity analysis is performed with the models, and the modelresults are compared with ammonia emission experiments at a swinewaste storage and treatment lagoon in NC using a dynamic emissionflux chamber.Results of model predictions of emission flux indicate an exponential increase in ammonia flux with increasing lagoontemperature and pH, a linear increase with increasing lagoontotal ammoniacal nitrogen (TAN), and a secondary degree increasewith the increasing wind speed. In addition, the fluxes predictedby Model I are consistently larger than fluxes predicted by Model II. Experimental values of flux agreed well with model predictions, with the experimental values lying in different positions between the two model predictions under different physical and chemical conditions. Further, when compared to diurnal and seasonal experimental flux values, Model I corroborates the results in calm meteorological conditions (windspeed U10 = 1.5 m s^-1). However, the observed results are better predicted by Model II during unstable conditions, when wind speeds are higher than 2.0 m s^-1 and physical transfer process functions dominate.     

Tourists‘ and Locals‘ Preferences Toward Ecotourism Development in the Maya Biosphere Reserve,Guatemala

Ecotourism has been identified as a low impact means to provide income generating opportunities that are complementary to nature conservation as well as the welfare of the local population. The Maya Biosphere Reserve in Peten, Guatemala is one of Central America's largest and most isolated protected areas. And although the area is contains a well-visited archeological site, it has not been developed for ecotourism. In this study choice experiments are used to analyze the preferences toward alternative scenarios of ecotourism of two important stakeholder groups: foreign tourists and educated local residents. Results demonstrate that these two populations of have unequal but similar preference orderings, especially toward: improved national park management and the presence of guides for wildlife viewing. These stakeholder groups had different opinions toward paved access roads and the presence of illegal colonists within the protected area. Both populations favored an entrance fee toward the absence of an entrance fee. These preferences were generally consistent across other socioeconomic indicators. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.     

非均匀热环境下热舒适评价的两种方法及其关键技术

针对非均匀热环境下乘员热舒适性的评价问题,提出当量温度评价指标(EQT)和当量均匀温度评价指标(EHT);完成这两种评价指标的关键技术在于如何进行流场的三维Navier-Stokes方程与人体的生物热方程之间的耦合迭代。在进行数值计算时发现:流场计算时人体皮肤表面给温度分布(即提D irichlet问题)、人体的生物热方程求解时给热流密度分布(即提Neumann问题),采用其边界条件的提法后,使得非均匀热环境下的流场与人体生物热方程之间的大迭代容易收敛和稳定。典型算例表明:对同一种物理问题,尽管两种评价下所得到的当量温度不同,但得出的评价效果是一致的,这就从侧面显示了这两种评价方法的一致性与有效性。     

21世纪法学教学方程式

21世纪是知识经济时代、循环经济时代、经济全球化时代和法律全球化时代.要打造21世纪合格的法律人,法学院应打破传统的教学模式,重组教育资源,重构新的教学方程式,重排学科体系矩阵图,创建全新的教师-教的模式、学生-学的模式,以应对西方教育的入侵.     

建筑物地震损失估计方法对比分析

合理而准确地确定建筑物的地震损失是当今防震减灾研究的一个主要课题,也是地震保险费率厘定的前提.目前,我国已经在地震发生概率、场地类型、结构性能、财产分布等方面积累了许多震害统计资料.同时,不断应用地震学、抗震工程学和计算方法方面新的研究成果于地震损失的计算,形成了几种常见的损失估计思路和方法.这其中主要包括传统的地震灾害损失风险评估方法、基于动力可靠度的损失分析方法和基于结构性能的损失确定方法.从合理性和适用性的角度,对这3种方法进行了评述和比较,以此看出各种方法的优点和局限性以及分析思路的发展演变过程,并希望从中能够看出今后研究工作的一些方向.