Preference in flower visits and partitioning in pollen diets of stingless bees in an Asian tropical rain forest

Floral resource partitioning among stingless bees (Trigona, Meliponini, Apidae) in a lowland rain forest in Sarawak, Malaysia, was investigated using tree towers and walkways in a 4-year study that included a general flowering period. We obtained 100 collections of insect visitors to flowers of varying floral location and shape representing 81 plant species. The tendency of 11 species of stingless bees to visit specific flowers with a particular floral location and shape was analyzed by logistic regression analysis. This analysis showed that the proportion of flower visitor collections containing Trigona fuscobalteata and T. melanocephala differed according to floral location. The former was frequently collected at canopy and gap flowers, whereas the latter was most often collected at understory flowers. The analysis also suggested that T. erythrogastra was more rarely collected at shallow flowers than at deep flowers. Analysis of the pollen diets of T. collina, T. fuscobalteata, T. melanocephala, and T. melina revealed that similarity of pollen sources differed among the six permutated pairs of the four species. The lowest mean rank of similarity found was between T. fuscobalteata and T. melanocephala. This result supports the hypothesis that preference in visiting flowers in different locations leads to pollen resource partitioning. Received: May 14, 1997 / Accepted: April 23, 1999     

Effects of sterile insect releases on a population under predation or parasitism

Summary A continuous-time differential equation model was constructed which describes the population dynamics of a predator prey system in which sterile prey are released in a program designed to eradicate or reduce the prey population. It was found that the dynamics of the system behave quite differently when predators are present. Two conditions were found which have differing implications for the control program. If the predators still exist when the wild prey population declines to extinction, then the SIRM is assisted by the predators, sometimes to a considereble extent. If the predators decline to extinction before the wild prey population goes extinct, then the predators may or may not assist the SIRM depending on the parameters of the system. If the predators do assist the SIRM, then a potentially dangerous situation exists in which an explosion of the prey population could occur after the predators go extinct. Predator polyphagy would probably minimize this danger of an explosion since it would stabilize the predator population.     

克拉申第二语言习得理论引论

克拉申第二语言习得理论作为语言习得的重要理论,主要来自人们对语言学习者认知过程和心理的研究。文章介绍克拉申第二语言习得理论的背景、构成,以及克拉申第二语言习得理论的局限性,并指出其在语言学界的重要意义。     

我国行政事业单位国有资产管理探析

行政事业单位资产是我国国有资产的重要组成部分,在履行政府职能、加强公共管理、实施宏观调控、推动经济建设等方面发挥着重要作用。随着经济体制改革的深化,行政事业单位国有资产管理体制改革成为不可回避的一个紧迫问题。这涉及到行政事业单位国有资产的监管问题、如何发挥行政事业单位国有资产的社会效益问题、怎样防止国有资产的流失问题等。     

ECM-IS视角下移动政务APP用户持续使用意愿影响因素研究

随着“互联网+”时代的到来,移动政务APP快速发展,但也存在功能单一、满意度不高、用户持续使用意愿较低的问题,要促使其健康发展,必须重视用户的使用体验和使用意愿。本研究以ECM-IS模型理论为基础,构建了移动政务APP用户持续使用意愿影响因素模型,据此设计调查问卷并进行实证研究。研究结果显示,移动政务APP的系统质量是满足用户期望的重要因素,而用户感知对于提升用户的满意度以及促使持续使用具有重要的意义,其中,感知便利性和感知有用性的积极作用尤为明显。最后,从促使用户持续使用的角度,提出了完善移动政务APP系统功能、突出实用优势,兼顾趣味功能,以及重视用户感知、强调人文关怀等对策和建议。     

业主大会网络运行模式探究

业主大会作为住宅小区的自治组织,在运行中存在会议召开难、业主决策难等的问题,在小区公共事务治理中未能充分发挥作用。随着信息技术的逐渐成熟,通过网络使业主参与到小区公共事务治理中成为业主大会运行的新模式。比较官方组织的业主公共决策平台和民间自发组织的社区公共交流平台,前者更适宜安放业主大会的法律定位,其决议的效力更具有权威性。因此,在合理注意网络安全的前提下,未来业主大会运行模式的发展方向应当是依托民间网络平台,加大官方设立的业主公共决策平台建构,以推动业主大会的健康发展和社区建设的和谐稳定。     

中国-东盟自由贸易区中的易货贸易

《中国-东盟全面经济合作框架协议》第一部分有关贸易条款中,涵盖了易货贸易这种重要的贸易方式。在概述现代易货贸易的涵义、我国易货贸易现状的基础上,探讨其在巩固和发展中国-东盟自由贸易区中的意义,以及可采取的应对措施。     

水气分离集成井降水强夯法试验研究

为了克服降水强夯法处理深度小、降水时间长的缺陷,结合扬中灏港通用码头软土地基处理工程,改进了传统降水强夯工艺,采用水气分离集成井降水联合强夯法进行加固处理。通过在常规真空井点降水强夯和改进降水强夯两个试验区开展现场监测和检测试验,对加固效果进行了对比评价分析,研究结果表明:水气分离集成井降水强夯工艺降水深度可达地表以下5~6 m,夯后孔压消散时间约为1~2天;地基加固后总地表施工期最大沉降量为0.606 m,可有效减小工后沉降;与常规井点降水强夯法相比,改进法加固后土体强度和地基承载力均有较大提高,地基加固效果优势明显。     

效果研究的新范式:认知传播学——“后媒介”视阈下的学科构建

认知传播研究可以追溯到媒介环境学派的媒介感知模式的提出,在当下媒介技术高速更迭所带来的社会化转型趋势中,找到了更加契合的社会生态发展空间,在认知科学与传播学的范式融合中完成跨学科的体系重构。认知传播既可作为研究对象,从传播行为的空间视角出发关照主体认知的内在结构和规律,探寻以认知为本质的传播活动的意义和价值;又可作为一种研究方法,将认知科学的研究成果、主体认知的本质规律用于解释传播现象及衡量传播效果。