共查询到20条相似文献，搜索用时 171 毫秒
1.
研究了一类具有功能反应和阶段结构的捕食模型。在此系统中食饵分幼年和成年两个阶段,捕食者仅捕食幼年食饵,并且考虑食饵和捕食者之间具有比率依赖功能反应。利用一些引理和比较定理,讨论系统在一定条件下的周期性和持久性。 相似文献
2.
梁桂珍 《新乡师范高等专科学校学报》2007,21(5):28-30
研究了比率型非自治的捕食者——食饵模型是两个具有竞争关系的捕食者种群捕食一个食饵系统的正概周期解的存在唯一性和全局吸引性。 相似文献
3.
4.
5.
研究了具有Beddington-DeAngelis和HollingⅣ的功能反应的捕食与食饵生态系统,该系统是两个具有竞争关系的食饵种群被一个具有年龄结构的捕食种群捕食.运用比较定理,得到了系统持续生存和捕食者灭绝的充分条件. 相似文献
6.
建立并研究了捕食者具有传染病的捕食-食饵模型。在加入自食因素后,该模型假设不仅捕食者捕食食饵,健康的捕食者同样会捕食患病的捕食者,还考虑了患病捕食者的恢复能力和食饵的庇护能力,更加符合实际情况。证明了系统解的有界性,对系统的非负平衡点进行了稳定性分析,并通过特征根法讨论了非负平衡点的局部稳定性。 相似文献
7.
讨论食饵具有非线性密度制约的HollingⅡ型功能性反应的捕食者-食饵系统，利用微分方程定性理论，得到了该系统不存在极限环的充分条件和存在唯一稳定的极限环的充要条件． 相似文献
8.
9.
利用重合度理论,研究一类食饵有扩散的脉冲Holling-Ⅲ型时滞捕食者—食饵系统,证明并得到了系统正周期解存在的充分条件。 相似文献
10.
应用计算机模拟的方法,研究了具有性别结构的两种群食饵—捕食者模型,得到了参数的稳定区域。分析结果对于具性别结构的食饵—捕食者种群的研究具有现实指导意义。 相似文献
11.
杨昕 《乌鲁木齐职业大学学报》2006,15(3):10-13
目前,循环经济蓬勃发展,在乌昌经济一体化的快速发展中对发展循环经济的经验不能盲目借鉴,必须结合实际,正确理解循环经济的涵义,做好推进循环经济发展模式前的摸底与调研工作,做好发展循环经济的基础工作。 相似文献
12.
张翠英 《苏州教育学院学报》2014,(6):87-89
高职院校应积极从学生的角度出发,坚持“以人为本”,进行“职业指导”课程的改革,根据学生成长规律安排课程教学、根据学生所学专业设计特色教学内容、根据学生特点采用多种教学方法、根据教学需求培养专业化的师资队伍、根据学生所学内容同步开展课堂外活动、根据课程教学开展有针对性的评价。 相似文献
13.
We highlight three ways of conceptualising and enacting academic development: firstly as authentic, practice-based activity, secondly in terms of a new transformative paradigm for academic development units (ADUs), and thirdly as a space for disruption. We illustrate these conceptualisations through our investigation of the practice of internal secondment of faculty to ADUs. We report our findings from a sector-wide survey of Scottish higher education institutions and a series of in-depth interviews with secondees and their managers in two Scottish universities. We recommend further investigations to identify new ways of enacting authentic, practice-based, transformative, and disruptive academic development. 相似文献
14.
假设载流子浓度按指数关系变化,认为注入电流为热电子电流和隧穿电流,通过引入电荷空间分布特征长度和有效迁移率,讨论了单层单极聚合物发光器件内部的输运性质.结果表明:(1)电荷空间分布特征长度对器件中的电场强度,电流有很大影响;(2)载流子迁移率在注入电极附近减小,而在另一电极附近增加.本文对这些现象给予了解释. 相似文献
15.
Deborah Fields Veena Vasudevan Yasmin B. Kafai 《Interactive Learning Environments》2015,23(5):613-633
We highlight ways to support interest-driven creation of digital media in Scratch, a visual-based programming language and community, within a high school programming workshop. We describe a collaborative approach, the programmers’ collective, that builds on social models found in do-it-yourself and open source communities, but with scaffolding structures that support students’ learning. We analyze the work of a class of high school student collectives engaged in programming music videos as part of a collaborative challenge in the online Scratch community. Our multi-level analysis focused on students’ learning specific programming concepts, effects of collaborative and task design on learning, and their personal reflections on collaboration and media creation. We address how these overlapping collaborative experiences point to the value of “nested collectives,” or multiple levels of designed-for collaboration. We also highlight a needed shift from a focus on computation to computational participation, highlighting the innately social aspects of media creation. 相似文献
16.
We propose a simple theoretical model which shows how the combined effect of wage uncertainty and risk aversion can modify the individual willingness to pay for a HE system financed by an ICL or a ML. We calibrate our model using real data from the 1970 British Cohort Survey together with the features of the English HE financing system. We allow for individual heterogeneity by considering different family backgrounds and occupations. We find that graduates from poor families, males and graduates working in the private sector are more willing to pay to switch to an ICL. Using the UK Labour Force Survey we evaluate the distributive effects of our model. We compute the repayment burdens and taxpayer subsidies for average, low and high earnings graduates. The results confirm the important insurance benefits of an ICL compared to a ML, with lower burdens and higher subsidies for poorer graduates. 相似文献
17.
18.
We used a randomized quasi-experimental design to test the effectiveness of three types of perspective-taking condition in a forgiveness education program. Allport’s Contact Hypothesis was used as a framework for the study design. Eighth graders (n?=?132) in an urban Midwestern city were invited to participate. We evaluated the effectiveness of perspective-taking approaches in promoting forgiveness and reducing prejudice, anger and emotional reactivity. We also explored the effects of forgiveness education across socially and culturally diverse groups. We did not find differences between the perspective-taking conditions; however, all three groups improved on both forgiveness and prejudice. We also found the pattern of outcomes was different for the African American participants than for the European American participants. Implications for research and education are discussed. 相似文献
19.
What trajectories do students follow as they connect their observations of electrostatic phenomena to atomic‐level visualizations? We designed an electrostatics unit, using the knowledge integration framework to help students link observations and scientific ideas. We analyze how learners integrate ideas about charges, charged particles, energy, and observable events. We compare learning enactments in a typical school and a magnet school in the USA. We use pre‐tests, post‐tests, embedded notes, and delayed post‐tests to capture the trajectories of students’ knowledge integration. We analyze how visualizations help students grapple with abstract electrostatics concepts such as induction. We find that overall students gain more sophisticated ideas. They can interpret dynamic, interactive visualizations, and connect charge‐ and particle‐based explanations to interpret observable events. Students continue to have difficulty in applying the energy‐based explanation. 相似文献
20.
易慧玲 《信阳师范学院学报(哲学社会科学版)》2015,(2):59-63
微信作为一种信息传播的新途径,具有传播速度快、受众广泛、不受时间限制等特点。在旅游活动中,微信不仅成为旅游者个体分享旅游体验的媒介,而且受到旅游企业及政府部门的关注,并将其作为宣传旅游目的地,进行旅游目的地或旅游产品营销和推广的方式。旅游局开通旅游微信平台,将其作为发布当地旅游信息的平台,具有成本低、管理易、形式灵活且影响显著的特点。贵州省是欠发达地区,其旅游局建立的微信平台存在无专业人员管理、发布的微信内容原创性欠缺等问题,只有通过聘用专业人员管理,增加微信内容原创性以及丰富微信平台活动等手段解决问题,才能使微信成为宣传贵州省旅游资源的重要媒介。 相似文献