寄生在营养级间的传播及其对物种间共存的影响

寄生可以在营养级间传播,且能够操纵宿主对种群动态产生影响,宿主操纵的目的是为了促进寄生自身的传播,在这个过程中会导致宿主的行为、生理、心理、特征等方面出现一定的减弱,这会改变物种之间的相互作用。建立两种微分方程宿主操纵模型,利用MATLAB软件对模型进行数值模拟,可以得出：寄生调节已感染食饵更易被捕食,这能够促进其与捕食者之间的共存,缓解两者之间的对立冲突,主要方式是通过牺牲更多的已感染食饵满足捕食者的能量需要,进而释放出一部分易感染食饵,从而实现种群生存;而寄生调节的已感染捕食者更易死亡,这会使得易感染捕食者更占优势,随着操纵强度的增大,会出现食饵灭绝的情况。从而得出结论：宿主操纵有利于被操纵对象的续存。这对指导物种续存、丰富物种类别、保护健康生态环境具有重要作用。     

恐惧和庇护所对捕食系统的影响

建立了一类捕食者受到恐惧,食饵受到庇护所的捕食模型,其中恐惧和庇护所都影响捕食者的捕食率.通过分析所建立捕食模型的动力学性态,得出在捕食者受到恐惧的基础上,对食饵建立庇护所可以改变平衡点的位置及其稳定性.此研究结果对濒危物种的保护有着重要意义.     

具有脉冲效应两捕食一食饵者系统的数学分析

讨论了具有功能性反应和脉冲效应的一食饵两捕食者系统.运用脉冲微分方程的Floquent理论和比较定理,得到了食饵灭绝周期解全局渐近稳定和系统持续生存的条件.最后,通过数值模拟,进一步阐明了系统的结论.     

一类时滞两食饵一捕食者系统的周期解

对带有时滞的两食饵一捕食者系统进行研究.讨论了非负平衡点的性质,运用Hopf分岔方法,以时滞τ为参数给出了系统经历Hopf分岔的条件,得到了构成系统的三物种具有周期循环生物现象的结论.     

线性平移在捕食者—食饵数学模型稳定性分析中的应用

文中通过线性平移的方法分析和讨论捕食者一食饵系统的数学模型平衡点的稳定性态,来描述和研究捕食种群和食饵种群规模随时间的变化趋势,并且用MATLAB进行了模拟,数值模拟和理论分析相一致．     

一类基于比率依赖的捕食-食饵模型的定性分析

研究了一类两物种间的捕食—食饵模型,其功能反映函数为比率依赖型.首先运用抛物型方程的比较原理得到系统的一个全局吸引子,然后通过椭圆型方程的极值原理和特征值方法对平衡态解的性质加以分析.最后证明了共存解的存在性和稳定性.     

思维领域中时间和空间的尺度

时间、空间观念的形成由最初的感官、知觉形式转而成为今天科学的分析,在思维领域中包含着自然、物种和社会尺度的演化历程。自然、物种和社会尺度在思维领域所形成的认知、心理结构中遵循相似性规律的迁移,以及与此并行的变形和变异,影响到人们对时间、空间的不同认识。     

具性别结构的两种群食饵—捕食者模型的计算机模拟研究

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。     

一类捕食者-食饵交错扩散模型解的整体存在性

应用能量估计方法和bootstrap技巧证明一类含两种捕食者和两种竞争食饵的捕食者-食饵交错扩散模型在空间雏数小于10时整体解的存在性．     

捕食者死亡率具比率型的捕食者-食饵模型

建立捕食者死亡率依赖于捕食者与食饵的比率的捕食-食饵模型,分别考虑捕食者的功能性反应为双线性型与比率依赖型的情形,在一定条件下得到正平衡点全局稳定和极限环的存在性,并进行了数值模拟．     

Numerical simulation of a direct internal reforming solid oxide fuel cell using computational fluid dynamics methodas

A detailed mathematical model of a direct internal reforming solid oxide fuel cell (DIR-SOFC) incorporating with simulation of chemical and physical processes in the fuel cell is presented. The model is developed based on the reforming and electrochemical reaction mechanisms, mass and energy conservation, and heat transfer. A computational fluid dynamics (CFD) method is used for solving the complicated multiple partial differential equations (PDEs) to obtain the numerical approximations.The resulting distributions of chemical species concentrations, temperature and current density in a cross-flow DIR-SOFC are given and analyzed in detail. Further, the influence between distributions of chemical species concentrations, temperature and current density during the simulation is illustrated and discussed. The heat and mass transfer, and the kinetics of reforming and electrochemical reactions have significant effects on the parameter distributions within the cell. The results show the particularchar acteristics of the DIR-SOFC among fuel cells, and can aid in stack design and control.     

Effects of spatial aggregation on forest landscape model simulation in Northeastern China

Issues of scale and aggregation become important when large range of space and time scales is considered in landscape models.However,identifying appropriate levels of aggregation to accurately represent the processes and components of ecological systems is challenging.A raster-based spatially explicit forest landscape model,LANDIS,was used to study the effects of spatial aggregation on simulated spatial pattern and ecological process in Youhao Forest Bureau of the Small Khingan Mountain in Northeastern China.The model was tested over 500 simulation years with systematically increased levels of spatial aggregation.The results show that spatial aggregation significantly influences the simulation of fire disturbance,species abundance,and spatial pattern.Simulated fire regime was relatively insensitive to grain size between 30 m and 270 m in the region.Spatial aggregation from 300 m to 480 m dramatically decreased fire return interval (FRI) and increased mean fire size.Generally,species abundance and its aggregation index (AI) remained higher level over simulation years at the fine-grained level of spatial aggregation than at coarser grains.In addition,the simulated forest dynamics was more realistic at finer grains.These results suggest that appropriate levels of spatial aggregation for the model should not be larger than 270 m.     

Numerical simulation of a direct internal reforming solid oxide fuel cell using computational fluid dynamics method

A detailed mathematical model of a direct internal reforming solid oxide fuel cell （DIR-SOFC） incorporating with simulation of chemical and physical processes in the fuel cell is presented. The model is developed based on the reforming and electrochemical reaction mechanisms, mass and energy conservation, and heat transfer. A computational fluid dynamics （CFD） method is used for solving the complicated multiple partial differential equations （PDEs） to obtain the numerical approximations. The resulting distributions of chemical species concentrations, temperature and current density in a cross-flow DIR-SOFC are given and analyzed in detail. Further, the influence between distributions of chemical species concentrations, temperature and current density during the simulation is illustrated and discussed. The heat and mass transfer, and the kinetics of reforming and electrochemical reactions have significant effects on the parameter distributions within the cell. The results show the particular characteristics of the DIR-SOFC among fuel cells, and can aid in stack design and control.     

The Right “Fit”: Exploring Science Teacher Candidates’ Approaches to Natural Selection Within a Clinical Simulation

Teachers and students struggle with the complexities surrounding the evolution of species and the process of natural selection. This article examines how science teacher candidates (STCs) engage in a clinical simulation that foregrounds two common challenges associated with natural selection—students’ understanding of “survival of the fittest” and the variation of species over time. We outline the medical education pedagogy of clinical simulations and its recent diffusion to teacher education. Then, we outline the study that situates each STC in a one-to-one interaction with a standardized student who is struggling to accurately interpret natural selection concepts. In simulation with the standardized student, each STC is challenged to recognize content misconceptions and respond with appropriate instructional strategies and accurate explanations. Findings and implications center on the STCs’ instructional practices in the simulation and the use of clinical learning environments to foster science teacher learning.     

具有阶段结构的单种群模型概周期正解的存在唯一性及全局吸引性

文章用一种新的方法研究了一类具有时滞的概周期单种群阶段结构模型,得到了模型存在唯一的正的概周期解,且此概周期解是全局吸引的.最后文章给出了数值模拟,支持了理论结果.     

进化状态可控型遗传算法

遗传算法是模拟自然界生物进化过程的一种优越的全局优化方法,但由于遗传操作的随机性,其进化过程是"暗箱操作".本文提出进化状态可控、遗传操作具有智能功能的方法,并通过计算机模拟,验证了该算法的有效性.     

香菇热风干燥中质传递模拟与试验研究

根据非平衡态热力学和相平衡理论,建立了香菇热风干燥内部传质模型、传热模型,该模型充分考虑了传热与传质之间的相互藕合关系,进行香菇干燥传质模拟计算,并与干燥试验数据进行对比,结果表明：模拟值和实测值十分接近,二者的最大相对偏差小于7％,模拟结果符合对流干燥中多孔介质内部水分迁移规律,以及干燥过程中产生的表低内高水分分布规律。     

Simulink在电力电子技术教学中的应用

对目前常用的教学仿真软件的优缺点进行了分析比较,选择Maflab环境下Simulink仿真工具对电力电子技术中的SPWM调制技术进行了仿真．结果表明,将该软件模块化、可视化的特点应用到电力电子技术课程的教学中,可以帮助学生更直观、清晰地学习和理解一些较复杂的算法问题,在电力电子技术教学中具有一定的推广价值。     

虚拟仿真教学系统学习效果的影响因素研究

针对虚拟仿真教学系统如何影响学习者学习效果机制不明的问题,文章基于建构主义学习理论,构建了虚拟仿真教学系统学习效果的影响机制模型。在此基础上,文章使用系统日志数据,从教学内容、虚拟仿真技术、学习者特征三个维度探讨虚拟仿真教学系统对学习效果的影响,并提出7个研究假设。随后,文章以江苏科技大学企业管理虚拟实景实验教学系统为例进行了实证研究,对7个研究假设进行了一一验证,结果发现:学习者的专业素养正向影响操作能力表现与学习效果;任务复杂性与操作能力表现之间呈倒U型关系;虚拟仿真技术分别调节了专业素养、任务复杂性与操作能力表现之间的关系。最后,文章针对虚拟仿真教学系统的具体应用提出建议,以期提升虚拟仿真教学系统在高校应用的教学效果。     

74LS163同步置数法构成任意进制计数器的Multisim仿真

文章介绍了利用集成4位二进制计数器74LS163同步置位法构成任意进制计数器的设计方法,并进行了按自然态序计数、按逆排序计数、按任意排序计数的Multisim仿真设计,同时用不同颜色探针显示计数过程和计数结果,直观形象地描述出计数器的状态变化特点,分析了不同方法仿真结果的正确性,指出了Multisim中74LS163计数器时钟触发方式与实际芯片的不同。