Are savannas patch-dynamic systems? A landscape model

Savannas are ecosystems characterized by the coexistence of woody species (trees and bushes) and grasses. Given that savanna characteristics are mainly formed from competition, herbivory, fire, woodcutting, and patchy soil and precipitation characteristics, we propose a spatially explicit model to examine the effects of the above-mentioned parameters on savanna vegetation dynamics in space and time. Furthermore, we investigate the effects of the above-mentioned parameters on tree–bush–grass ratios, as well as the degrees of aggregation of tree–bush–grass biomass. We parameterized our model for an arid savanna with shallow soil depth as well as a mesic one with generally deeper and more variable soil depths. Our model was able to reproduce savanna vegetation characteristics for periods of time over 2000 years with daily updated time steps. According to our results, tree biomass was higher than bush biomass in the arid savanna but bush biomass exceeded tree and grass biomass in the simulated mesic savanna. Woody biomass increased in our simulations when the soil's porosity values were increased (mesic savanna), in combination with higher precipitation. Savanna vegetation varied from open savanna to woodland and back to open savanna again. Vegetation cycles varied over ∼300-year cycles in the arid and ∼220-year cycles in the mesic-simulated savanna. Autocorrelation values indicated that there are both temporal and spatial vegetation cycles. Our model indicated cycling savanna vegetation at the landscape scale, cycles in cells, and patchiness, i.e. patch dynamics.     

Economic resilience to natural and man-made disasters: Multidisciplinary origins and contextual dimensions

Economic resilience is a major way to reduce losses from disasters. Its effectiveness would be further enhanced if it could be precisely defined and measured. This paper distinguishes static economic resilience—efficient allocation of existing resources—from dynamic economic resilience—speeding recovery through repair and reconstruction of the capital stock. Operational definitions are put forth that incorporate this important distinction. The consistency of the definitions is examined in relation to antecedents from several disciplines. The effectiveness of economic resilience is evaluated on the basis of recent empirical studies. In addition, its potential to be enhanced and eroded is analyzed in various contexts.     

Do environmental regulations disproportionately affect small businesses? Evidence from the Pollution Abatement Costs and Expenditures survey

This paper examines whether the impact of environmental regulations differs by the size of the business. We consider the net effect of statutory, enforcement, and compliance asymmetries by estimating the relationship between plant size and pollution abatement expenditures, using establishment-level data on U.S. manufacturers from the Census Bureau's Pollution Abatement Costs and Expenditures (PACE) survey and from its Annual Survey of Manufactures and Census of Manufactures. We model establishments' pollution abatement operating costs (PAOC) per unit of economic activity as a function of establishment size, industry, state, and year. Our results show that PAOC intensity increases with establishment and firm size.     

大型商业建筑中的性能化设计问题探讨

本文分析了大型商业建筑的建筑特点、火灾特点及火灾危害性,并基于性能化防火设计的理念,针对某大型商场的建筑特点和性能化问题,提出了通过设置防烟走廊阻止火灾高温烟气进入作为疏散临时安全区的中庭的设计方法。在合理估算建筑内火灾和人员荷载的基础上,选用合适的模型,通过对火灾情况下的烟气蔓延和人员疏散进行数值模拟和分析,验证了防烟走廊的设置可有效提高中庭的防火安全性能。     

Emissions cap or emissions tax? A multi-sector business cycle analysis

We develop a multi-sector business cycle model to analyze stochastic implications of reducing CO₂ emissions with carbon permits or with carbon taxes in the presence of multiple sources of macroeconomic uncertainty. The model is calibrated to reflect the U.S. experience. As in previous studies, using a single-sector version of our model, we find that the cap regime generates lower volatility of real variables than the tax regime, but the latter may be preferable from the welfare perspective. Still, our multi-sector analysis points to the importance of the origin of the shocks in the ranking of the two instruments and to the desirability of going beyond a single-sector analysis in evaluating their merits. We find no significant difference between the cap and the tax regimes when shocks come from non-energy sectors. In contrast, the cap has lower volatility but higher welfare costs than the tax for the shocks to energy production.     

沈阳市商业性污染防治对策

本文在论述沈阳市城市景观空间格局的基础上,从商业景观的布局和产业组成等方面探讨了商业性污染产生的原因及其基本规律,最后提出了加强沈阳市商业景观建设及商业性污染防治的对策。     

Energy and exergy analysis of a combined Brayton/Brayton power cycle with humidification

ABSTRACT

First and second law approaches have been used to analyze the performance of a humidified Brayton/Brayton power cycle. The energy efficiency and exergy destruction rates consistently improved when the combustion temperature was increased. Both performance indicators improved, reached an optimum, and then deteriorated when the topping cycle pressure ratio increased, while their sensitivity to the bottoming cycle pressure ratio depended on the humidification rate used at the bottoming cycle. Upon increasing the mass flowrate of air through the bottoming cycle, the energy efficiency of the power cycle increased linearly, while the irreversibility generation had a non-monotonic variation. In all cases, a higher degree of humidification always resulted in greater first and second law performances.     

Towards a SOLAP-based public participation GIS

In this paper, we describe how spatial on-line analytical processing (SOLAP), a specific category of business intelligence technology especially adapted to geospatial data, can help to improve the technological side of public participation GIS applications. Based on two simulated cases of realistic scenarios of a public audience, this paper aims at demonstrating the relevance of this SOLAP technology to support and improve the interactive access and analysis of multi-scale, multi-epoch geospatial information (and indirectly public involvement) for an environmental management PPGIS application.     

Pressure-assisted chelation extraction of lead from contaminated soil

Soil contamination by metallic elements including lead occurs frequently. Contaminant metals in soil pose a serious risk to public health and groundwater supplies. Extraction using chelants is seen as a remediation option; however, it is often hampered by access to the contaminants that are shielded by the soil matrix. We have developed a novel extraction technique that utilizes a mildly elevated pressure in consecutive cycles of compression and decompression along with a chelating agent for the soil slurry. Complete extraction of 3300 mg/kg of Pb from soil was achieved by 100 mM of EDTA (ethylenediaminetetraacetic acid) in 10 min using 20 pressure cycles at 150 psi (10 atm). Extraction was studied according to pressure, number of pressure cycles, chelant concentration, solid content, pH, agitation, and use of consecutive washings. Heightened extraction is attributed to fracturing of the soil particles that leads to enhanced contaminant exposure to the chelating agent.     

高职商务英语专业内容依托型教学模式初探

内容依托教学(CBI)是融语言学习与内容学习为一体的教学方式。在高职商务英语专业采用CBI教学模式,以真实的商务活动为背景,使语言学习和专业技能的培养与商务实践相结合,有助于形成"懂商务、会英语"的复合型应用人才培养模式。但目前CBI的实施还面临着教师素质、教学效果以及评估体系等方面的问题,可通过培养专业师资、制定合理教学进度等方法逐步完善。