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Abstract: We developed a simple model of Pinus strobus L. stand dynamics to compare the impacts of different temporal arrangements of surface fires designed to reflect the application of fire as both an essential ecosystem process (natural fire) and as an efficient means of producing specific habitat features or other values (optimal fire). We used a stochastic simulation model of fire processes to estimate the mean fire-return interval that would maximize stand structural diversity. We investigated trade-offs between structural diversity and temporal population stability associated with changes in the fire interval and used a deterministic version of the model to explore the effects of scheduling fires at fixed intervals. In stochastic simulations, maximum structural diversity occurred at intermediate levels of disturbance (40-year mean fire interval). When fires were scheduled at fixed intervals, a longer, 100-year return interval maximized diversity. Mean fire-return interval was a mitigating factor in the diversity-stability relationship, which changed from positive to negative as the fire interval was reduced progressively from 250 to 5 years. As an alternative to scheduling fires at specified mean intervals, we developed a goal-programming model (a form of linear programming model) and used it to identify an optimal fire schedule for achieving habitat and visual-quality objectives. In comparison with the 40-year stochastic mean fire interval, which maximized structural diversity, the optimal schedule produced comparable levels of both diversity and fire frequency. Our results show how simulation and goal-programming models can be used to evaluate prescribed fire-scheduling alternatives and to explore the comparative advantages of natural and optimal fire-management approaches. 相似文献
564.
Small and medium enterprises (SMEs) are under pressure to adopt sustainable practices in their business due to increasing environmental challenges. This study aims to identify and prioritize the solutions to overcome the barriers in the implementation of ecodesign practices in SMEs. This study helps the companies to develop and implement the strategies on priority using higher ranked solutions. In this study, a framework is proposed that is based on fuzzy analytical hierarchy process and fuzzy technique for order preference by similarity to ideal solution to rank the solutions that overcome the barriers in ecodesign implementation in SMEs. The proposed framework is illustrated by conducting a case study of an Indian ring and piston manufacturing company. This framework provides an effective support in the decision-making of the company for producing eco-friendly products through the implementation of ecodesign practices. Results of this study emphasize that training of designers to use different ecodesign tools is an essential practice for SMEs. 相似文献
565.
拟威克酵母产生表面活性剂的发酵条件 总被引:1,自引:0,他引:1
通过单因子试验和正交试验,对拟威克酵母WickerhamielladomercqiaeY2A产生槐糖脂的发酵培养基组成和发酵条件进行了优化.培养基组成为:8.0%葡萄糖、8.0%菜子油、0.3%酵母粉;发酵条件为:初始pH值6.0、接种量2.5%、发酵时间120h.在此条件下,槐糖脂产量可达到41.3gL-1.图4表5参16 相似文献
566.
介绍了在基因算法基础上改进的加速基因算法(AGA),并通过环境非线性数学模型参数估计实例对该法与传统参数估计方法进行了比较。初步结果表明,AGA法直观、简便、拟合精度高、通用性强,易为广大环境工程技术人员理解和使用。 相似文献
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对一个磷肥厂周围12个村庄的人发、粮食和饮水硒、碘、氟进行了测定,利用改进的模糊数学中的群体识别法对以上数据进行分析,所得结果表明,受污染较重的几个村庄人体硒、碘、氟含量确实受到来自磷肥厂的大气高浓度硒、碘、氟的直接影响. 相似文献
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分析了矿区开发对环境的影响,在此基础上建立了评价矿区环境质量的分层次指标体系和模糊综合评价方法,并将矿区环境质量分为5个等级:清洁,较清洁,轻污染,中污染和重污染。通过利用模糊评价使复杂的定性问题定量化,更直观简单地掌握矿区环境的治理状态,并利用此方法对潞安矿区的环境质量进行了评价。 相似文献