一种改进的多学习教与学优化算法

针对传统教与学算法在解决复杂多峰函数优化问题时,具有局部最优且搜索开发能力较差的缺点,提出了一种改进的多学习教与学优化算法,新算法为学员的每一维加入不同的教学因子,设计了基于学员均值比较的教师选择策略和向教师及学员学习的多学习策略。基于多个单峰和多峰函数的仿真结果表明,新算法跟传统的、改进的教与学算法相比,在稳定性、寻优精度和收敛速度方面更具优势。     

The relationship between environmental management strategies and environmental compliance at Marine Corps installations

Environmental compliance requirements periodically impact the military's ability to use all installation resources. In response, environmental management strategies have been developed to ensure compliance and allow site closure. This study examines the relationship between environmental management strategies and environmental compliance at U.S. Marine Corps (USMC) installations via analysis of environmental compliance audit scores. Five environmental scores of interest from 1998 to 2004 audits—which include total compliance, total management, audit management, policy management, and training management—were subjected to statistical analysis. Results showed the USMC met environmental compliance and management standards, despite limited resources. High management strategy scores were moderately correlated with high total compliance scores. Total management scores improved over time, and noncompliance was most often associated with a lack of resources and plans. © 2006 Wiley Periodicals, Inc.     

Brominated flame retardant concentrations and trends in abiotic media

BFR burdens in abiotic media have been less studied than in biota, despite their essential value as an aide to identifying sources, temporal and geographic trends and exposure routes. Many polymer products consist of several percent by weight of BFRs. Global trade in these can result in rapid and wholesale BFR movement. Loss from in-use products of nonreactive BFRs may be important, particularly in respect to indoor exposure. In the case of BDE-209, discharges from publicly owned treatment works may be substantial. BFR burdens in air, water and sewage sludge respond rapidly to changes in environmental BFR inputs. PBDEs have been the most widely studied. In many locales PBDE burdens in these media now surpass those of PCBs. Air and water near sources and urban areas are typically enriched relative to rural locales. The more volatile PBDEs dominate in the vapor phase, while BDE-209 typically predominates on particulates. Evidence exists for long-range transport of the more volatile PBDEs. A greater diversity of BFRs (mostly PBDEs, HBCD and TBBP-A) has been detected in sewage sludges. Land application of these sludges on agricultural fields is one conduit for soil contamination. In general, environmental concentrations of BDE-209 appear to be increasing, while penta-BDE burdens in Europe may have peaked. Sediments function as longer-term integrators of environmental burdens. Concentrations of common BFRs therein may be substantial near point sources. Evidence for debromination in the environment has been limited to date. However, some laboratory and field observations suggest it is possible to a limited extent.     

Diet quality affects an attractive white plumage pattern in dark-eyed juncos (Junco hyemalis)

Sexually selected traits that act as signals of quality often display some degree of condition dependence. In birds, condition dependence of ornamental plumage is often mediated by production costs related to acquisition or allocation of dietary resources. White plumage ornaments, however, have often been assumed to be inexpensive because their production requires neither pigment nor specialized feather structure. In male dark-eyed juncos (Junco hyemalis), the size of a white patch on the tail contributes to attractiveness and mating success. Using captive males, we examined the effects of diet quality on the size and brightness of the tail-white patch. After removing four tail feathers to induce replacement, we maintained subjects on a subsistence (low-protein) or enriched (high-protein) diet while induced feathers grew. Birds that received an enriched diet grew their feathers more quickly and grew larger, brighter white patches. Feather growth rate was positively correlated with the increase in the size of the tail-white patch, a relationship that was stronger in the subsistence diet group. However, within diet treatments, faster-grown feathers were slightly duller. Taken together, these results suggest that variation in diet quality may lead to condition-dependent expression of tail white and that condition dependence may be stronger in more stressful environments. We suggest a mechanism by which increased feather growth rate may lead to an increase in the size of the tail-white patch and discuss potential trade-offs between signal size and brightness.