基于生态位理论的国际承包商竞争力研究

基于组织生态学视角,采用2011 年度国际建筑市场顶级225 家承包商数据,对我国的国际承包商生态位及竞争力进行研究。结果表明我国顶级承包商在国际建筑市场上占有重要市场份额,在国际建筑市场的发展上具有举足轻重的地位,实力不断增强,总体来讲处于竞争优势地位;主要涉足领域包括房屋建筑、能源、交通等传统行业,而对于工业和电讯方面涉及较少,处于竞争劣势地位。针对此情况为中国承包商在拓展国际建筑市场方面提供建议。     

多峰函数优化的自适应小生境克隆选择算法

为了解决de Castro在2000年提出的CLONALG算法在多峰值函数优化时多峰搜索能力弱,训练时间长的问题,提出自适应小生境克隆选择算法（ANCSA）。该算法运用自适应小生镜技术、高频变异算子和小生镜免疫优势选择技术来对原有算法进行改进。新算法具有较强的全局和局部搜索能力,并且搜索时间较短。理论分析和仿真研究结果表明,相比CLONALG算法,提出的算法能够在较短的时间内搜索到所有的全局最优解和更多的局部最优解。     

基于遗传BP算法的神经网络在桩基检测中的应用

文中介绍了传统的遗传算法与BP算法,并分析了它们的不足。提出了一种将遗传算法和BP算法相结合的遗传BP算法,在遗传算法的群体设计中采用小生境技术,防止优秀个体早期退化。并将此方法应用于桩基检测中,实验证明了其正确性和有效性。     

基于元胞自动机的小生境微粒群算法

小生境技术的引入,提高了微粒群算法处理多峰函数优化问题的能力。本文提出了基于元胞自动机邻域的小生境微粒群算法,并通过对典型函数进行测试,实难结果表明,该算法在复杂函数(较难收敛函数)的优化中比基于环形结构的标准小生境微粒群算法要好。     

小波域多尺度ARMA模型的纹理分割方法

纹理特征的提取是纹理分割的关键。在小波域内,对图像建立多尺度自回归滑动平均(MultiscaleAutoregressiveMovingAverage,简称MARMA)模型,并用小生境遗传算法对MARMA模型进行参数估计,将估计出的参数向量作为纹理分割的特征标准。不同纹理图像的MARMA模型的参数向量具有较好的可分性,这就保证了最终纹理分割的质量。     

一种求解最小诊断代价的小生境遗传算法

在诊断操作相关的情况下,求解最小代价的诊断操作序列的过程是一个NP完全问题．目前的算法在建模和求解方面都不：是十分理想．通过对诊断问题进行更精确的建模和分析,提出了求解最小诊断代价的小生境遗传算法NGAMECD（Niche Genetic Algorithm for Minimum ECD）．实验证明,算法NGAMECD具有良好的性质,它需要的空间可以预测,较普通的遗传算法具有更好的隐式并行性,执行过程中群体能够保持多样性,在有效避免早熟问题的同时算法的收敛速度较快．NGAMECD与P／C更新算法相比,诊断代价减少了20％～50％．     

Diet and trophic niche space and overlap of Lake Ontario salmonid species using stable isotopes and stomach contents

Lake Ontario supports a diversity of native and non-native salmonids which are managed largely through stocking practices. Ecological changes (e.g., invasive species) altering the food web structure accompanied with shifts in prey abundance, necessitate understanding the trophic niches of Lake Ontario salmonids to aid in management. The objectives of this study were to quantify salmonid (5 species) trophic niches and dietary proportions using stable isotope ratios (δ¹³C and δ¹⁵N) of a large sample set (adult fish (>300?mm; n?=?672) and key offshore prey (5 species, n?=?2037)) collected across Lake Ontario in 2013. Estimates of prey based on stable isotope ratios were similar to stomach contents. Based on stable isotope ratios, non-native prey dominated salmonid diet; in particular alewife (Alosa pseudoharengus) constituted the majority (0.31 to 0.93) of all salmonid diets, and round goby (Neogobius melanostomus) contributed 0.26 and 0.19 of brown trout (Salmo trutta) and lake trout (Salvelinus namaycush) diets, respectively. Trophic niche overlap was high between all salmonids, except lake trout. The largest trophic niche overlap occurred between Chinook (Oncorhynchus tshawytscha), coho (Oncorhynchus kisutch), and Atlantic salmon (Salmo salar), and their reliance on alewife infers a strong pelagic foraging strategy. Lake, brown and rainbow (Oncorhynchus mykiss) trout had larger and/or more distinct trophic niches indicative of a more variable diet across individuals and utilizing different foraging strategies and/or habitats. Overall, Lake Ontario salmonids maintained a high reliance on alewife, and their potential for plasticity in diet provides important information to management regarding population sustainability.     

Applications of scaffolds: Tools for enhancing the immunomodulation of mesenchymal stromal cells

Exogenously delivered mesenchymal stromal cells (MSCs) are therapeutically beneficial owing to their paracrine effect; they secrete various cytokines, nucleic acids, and proteins. Multiple bioengineering techniques can help MSC cultures to release secretomes by providing stem cell niche-like conditions (both structurally and functionally). Various scaffolds mimic the natural extracellular matrix (ECM) using both natural and synthetic polymers, providing favorable environments for MSC proliferation and differentiation. Depending on material properties, either topographically or elastically structured scaffolds can be fabricated. Three-dimensional scaffolds have tunable substrate rigidities and structures, aiding MSC cultivation. Decellularized ECM-derived hydrogels are similar to the natural ECM, thus improving the paracrine effects of MSCs. Here, we discuss recent research on the application of scaffolds to maximize the immunomodulatory function of MSCs.     

基于生态位及其熵值模型的陕西省渭河流域用水结构特征

为了阐明陕西省渭河流域用水结构特征,实现水资源的合理配置,以该区域七市一区为研究对象,基于2001—2016年的用水数据,利用生态位理论构建了用水结构生态位及其熵值模型,揭示了各行政区用水结构及其相对于陕西省、全国的演变态势。结果表明:(1)七市一区农业用水生态位最高,工业、生活用水生态位次之;行政区间各用水类型生态位存在明显差异,其中渭南市、榆林市农业用水生态位级别最高,铜川市、延安市工业用水生态位级别最高,西安市在生活用水与城镇公共用水方面级别最高。(2)行政区各用水类型生态位宽度普遍大于陕西省及全国,其中农业用水生态位宽度分别是陕西省与全国的1. 15～2. 62、1. 36～3. 09倍,工业用水生态位宽度分别是陕西省与全国的0. 75～4. 13、0. 86～4. 71倍,反映出区域用水结构处于调整阶段且工、农业用水调整力度大于陕西省及全国平均水平。(3)相较于全国,陕西省农业用水与城镇公共用水处于扩充状态,生活用水与工业用水处于压缩状态;相较于陕西省,不同行政区各用水类型有扩充也有压缩。运用生态位理论能够全面、直观地反映陕西省渭河流域行政区用水结构的变化,方法简便、实用,具有可推广性。     

生态位理论在城镇职能体系优化中的应用研究

生态位理论是生态学最重要的理论之一，对自然和人类生态系统均具有重大的指导意义。作者在简要介绍生态位理论的基础上，将其引入到城镇职能体系规划之中，运用生态理论对城镇职能体系优化进行了初步性探讨。