求解最小生成树的一种小生境遗传禁忌算法

针对最小生成树问题,提出了一种小生境遗传禁忌算法。算法中使用Prfer数对生成树进行编码。在选择交叉之前使用小生境技术,使得被选中交叉的个体之间的适应值的距离大于一定的阈值,从而保证了个体的多样性。遗传变异算子使用禁忌搜索算法,提高了遗传算法的局部搜索能力,加快了算法的收敛速度。模拟实验结果证明该算法是有效的。     

基于EDA算法的机械手最优轨迹

遗传算法在机械手轨迹优化过程中存在一定的缺陷,为了获得较理想的运动轨迹,提出了基于EDA优化算法的机械手运动轨迹优化算法。由于EDA算法中仅使用选择和基因池重组算子,因而常会过早收敛。为了改变这种不足,提出一种改进的EDA算法(IEDA),IEDA算法中使用了小生境技术来保持解的多样性,斌使用簇的方法保存优良个体。通过实验仿真,所得优化轨迹令人满意,且表现出优良特性。     

基于小生境粒子群优化的船舶多路径规划方法

针对船舶全局路径规划中的多路径规划问题,提出一种基于小生境粒子群优化的多路径规划方法。借鉴遗传算法求解多峰函数的思想,在基本粒子群优化算法的基础上,引入小生境生成、隔离进化和交叉算子等策略,分别采用主群粒子进行区域划分,使用子群粒子完成区域内的局部寻优,从而实现船舶多路径规划。仿真结果表明,该方法能正确、有效地规划出多条最优及次优路径。     

Unrestricted ramping rates and long‐term trends in the food web metrics of a boreal river

Long‐term monitoring of the food web of a regulated hydropeaking river was conducted to assess if previously documented effects of changing ramping rates (RRs) were maintained with the addition of 6 years of data. Using carbon and nitrogen stable isotope analyses, we hypothesized that: (1) macroinvertebrates and fish inhabiting areas below peaking hydrodams would be higher in δ¹⁵N and lower in δ¹³C due to increased flow velocity and the influence of light respired dissolved inorganic carbon, relative to those sampled from areas with a natural flow regime; (2) the increase in δ¹⁵N of macroinvertebrates would lead a shorter food web length in the regulated river, but δ¹³C and niche width would be similar between the restricted and unrestricted RR periods (i.e., the BACI analysis); and (3) isotopic metrics (e.g., δ¹³C, δ¹⁵N, niche width [SEA_B], and food chain length [Δ¹⁵N]) would correlate with variations in flow characteristics through time. Consistent with previous analysis conducted over a shorter time period, a shift toward higher δ¹⁵N values was observed for both fish and invertebrates, but, contrarily, only invertebrates (not fish) had a lower δ¹³C value downstream of the dam. Over the long term, the before‐after‐control‐impact analysis found no effect of RRs on any of the food web metrics, implying that the change in operation did not affect the river food web. However, analysis of the time series data indicated that flow metrics and trophic metrics were often correlated, including a negative effect of RR (invertebrates) and discharge (fish) on food chain length. This study illustrates the difficulty in detecting changes in food web structure and function under changing flow regime influenced by natural and anthropogenic effects. As such, this study highlights the need for considering large spatial and temporal scales to differentiate between confounding effects of climate, natural variability, and altered flow regimes on food webs in regulated rivers.     

多模态函数优化的小生境蚁群算法及其仿真分析

结合蚁群算法基本原理,设计一种解决多模态函数优化问题的小生境蚁群算法(NACA),算法采用实数编码,通过对NACA仿真研究,并和相关算法的仿真结果进行比较分析,结果表明NACA具有参数易于选择、适应性强、收敛性好等优点,非常适合于求解同时具有多个最优解或需要搜寻局部最优解的多模态函数优化.     

求解高维多模优化问题的正交小生境自适应差分演化算法

针对传统优化算法在求解高维多模态优化问题时存在收敛速度慢、求解精度低的问题,提出一种基于正交设计与小生境精英策略的自适应差分进化算法ONDE。首先利用正交表产生初始种群,然后采用小生境精英策略来产生小生境种群(NP),并用小生境种群更新精英个体;接着应用拥挤裁剪避免种群陷入局部搜索,最后利用自适应差分变异算子改进了差分进化(DE)算法。通过对7个benchmark函数仿真验证,实验结果表明,算法在收敛速度、求解精度和稳定性方面都有较大优势。     

遗传算法在分布式OS-CFAR检测系统优化中的应用

针对一个3传感器分布式OS-CFAR检测系统，本文分别使用了基本遗传算法和改进的遗传模拟退火算法、小生境遗传算法进行优化搜索，给出了一组不同检测条件下的准最优搜索结果。结果表明，对于这一优化问题，遗传模拟退火算法和小生境遗传算法都具有较好的适应性，其中小生境遗传算法在搜索质量、稳定性和搜索速度上相对更好一些，是一种较理想的多传感器分布式OS-CFAR检测系统参数优化算法。     

试爆在新烟囱爆破拆除中的应用

新烟囱爆破拆除前的试爆效果表明爆破设计方案及参数达不到预期要求,分析发现烟囱内壁有强度较高的耐火砖。根据烟囱结构和材质强度,合理地调整爆破方案和爆破参数,如增加单孔装药量,在烟囱切口内壁增设药龛,使用内壁裸露爆破辅助主孔爆破等,取得了理想的爆破效果。     

一种自适应小生境分布性保持策略

 小生境技术被广泛应用在多目标进化的分布性保持方面.但是,小生境半径不易控制等限制了其在分布性保持等方面的发展.本文提出了一种自适应小生境分布性保持策略(Adaptive Niche,AN).AN通过对Pareto解集生成最小生成树来自适应调整小生境半径,同时扩大搜索小生境半径并改变计算方法使之能够识别小生境边沿的个体,便于对其修剪与评价.通过与NSGA-II,SPEA2在不同形状测试函数上进行对比实验,结果表明,AN能够对Pareto最优面进行高效地分布性保持.     

An Ecological Perspective of Listeria monocytogenes Biofilms in Food Processing Facilities

Listeria monocytogenes can enter the food chain at virtually any point. However, food processing environments seem to be of particular importance. From an ecological point of view, food processing facilities are microbial habitats that are constantly disturbed by cleaning and sanitizing procedures. Although L. monocytogenes is considered ubiquitous in nature, it is important to recognize that not all L. monocytogenes strains appear to be equally distributed; the distribution of the organism seems to be related to certain habitats. Currently, no direct evidence exists that L. monocytogenes-associated biofilms have played a role in food contamination or foodborne outbreaks, likely because biofilm isolation and identification are not part of an outbreak investigation, or the definition of biofilm is unclear. Because L. monocytogenes is known to colonize surfaces, we suggest that contamination patterns may be studied in the context of how biofilm formation is influenced by the environment within food processing facilities. In this review, direct and indirect epidemiological and phenotypic evidence of lineage-related biofilm formation capacity to specific ecological niches will be discussed. A critical view on the development of the biofilm concept, focused on the practical implications, strengths, and weaknesses of the current definitions also is discussed. The idea that biofilm formation may be an alternative surrogate for microbial fitness is proposed. Furthermore, current research on the influence of environmental factors on biofilm formation is discussed.