Many difficult engineering problems cannot be solved by the conventional optimization techniques in practice. Direct searches that need no recourse to explicit derivatives are revived and become popular since the new ...Many difficult engineering problems cannot be solved by the conventional optimization techniques in practice. Direct searches that need no recourse to explicit derivatives are revived and become popular since the new century. In order to get a deep insight into this field, some notes on the direct searches for non-smooth optimization problems are made. The global convergence vs. local convergence and their influences on expected solutions for simulation-based stochastic optimization are pointed out. The sufficient and simple decrease criteria for step acceptance are analyzed, and why simple decrease is enough for globalization in direct searches is identified. The reason to introduce the positive spanning set and its usage in direct searches is explained. Other topics such as the generalization of direct searches to bound, linear and non-linear constraints are also briefly discussed.展开更多
快速城市化与气候变化的共同胁迫使得高密度城市面临多重生态风险,包括城市热岛、洪涝灾害与空气污染等,这些生态问题不仅影响城市生态系统的稳定性,同时威胁人类福祉。因此,亟需对全球高密度城市的生态问题与应对策略开展研究。以Web o...快速城市化与气候变化的共同胁迫使得高密度城市面临多重生态风险,包括城市热岛、洪涝灾害与空气污染等,这些生态问题不仅影响城市生态系统的稳定性,同时威胁人类福祉。因此,亟需对全球高密度城市的生态问题与应对策略开展研究。以Web of Science和Scopus为文献检索数据源,通过系统性分析258篇文献揭示全球高密度城市生态问题的研究特征。首先,对全球高密度城市关键生态问题的数量分布与地理空间分布特征进行分析;其次,对三大生态问题的影响因素与尺度差异进行讨论,并提出城区与场地尺度下生态问题的应对策略;最后,研究表明城市三维形态、立体生态空间是未来生态问题的重点。研究结论表明:(1)亚洲地区对高密度城市生态问题关注度最高,城市热岛是全球高密度城市研究的热点问题;(2)景观格局特征与建成环境特征是城市热岛与洪涝的重要影响因素,生物物理特征与建成环境特征是空气污染的重要影响因素;(3)优化城市景观构成与空间配置可缓解高密度城市生态问题。研究结果为高密度城市开展生态研究与应对生态风险提供了重要启发。展开更多
基金supported by the Key Foundation of Southwest University for Nationalities(09NZD001).
文摘Many difficult engineering problems cannot be solved by the conventional optimization techniques in practice. Direct searches that need no recourse to explicit derivatives are revived and become popular since the new century. In order to get a deep insight into this field, some notes on the direct searches for non-smooth optimization problems are made. The global convergence vs. local convergence and their influences on expected solutions for simulation-based stochastic optimization are pointed out. The sufficient and simple decrease criteria for step acceptance are analyzed, and why simple decrease is enough for globalization in direct searches is identified. The reason to introduce the positive spanning set and its usage in direct searches is explained. Other topics such as the generalization of direct searches to bound, linear and non-linear constraints are also briefly discussed.
文摘快速城市化与气候变化的共同胁迫使得高密度城市面临多重生态风险,包括城市热岛、洪涝灾害与空气污染等,这些生态问题不仅影响城市生态系统的稳定性,同时威胁人类福祉。因此,亟需对全球高密度城市的生态问题与应对策略开展研究。以Web of Science和Scopus为文献检索数据源,通过系统性分析258篇文献揭示全球高密度城市生态问题的研究特征。首先,对全球高密度城市关键生态问题的数量分布与地理空间分布特征进行分析;其次,对三大生态问题的影响因素与尺度差异进行讨论,并提出城区与场地尺度下生态问题的应对策略;最后,研究表明城市三维形态、立体生态空间是未来生态问题的重点。研究结论表明:(1)亚洲地区对高密度城市生态问题关注度最高,城市热岛是全球高密度城市研究的热点问题;(2)景观格局特征与建成环境特征是城市热岛与洪涝的重要影响因素,生物物理特征与建成环境特征是空气污染的重要影响因素;(3)优化城市景观构成与空间配置可缓解高密度城市生态问题。研究结果为高密度城市开展生态研究与应对生态风险提供了重要启发。
