毒素在森林各分室循环的广义模型的变结构控制

利用广义系统变结构控制理论,研究了一个毒素在森林各分室循环的广义模型的变结构控制问题.首先,针对毒素在森林生态系统各分室的循环特征,构建了毒素在森林各分室循环的广义模型;其次,利用广义系统理论,对所建模型的平衡点进行了稳定性分析;最后,应用广义系统变结构控制理论设计了变结构控制器,使森林各分室中的毒素最终稳定到零点,使森林生态系统正常发展.     

一个具有突变体的种群模型的变结构控制

基于一个具有突变体的种群模型,提出了相应的控制模型.根据变结构控制原理,针对控制模型,分别设计了变结构控制器和近似变结构控制器,使突变体灭绝.最后通过数值仿真,验证了所得结论的正确性.     

一类具有非线性控制和基层具有饱和吸收率的恒化器藻类模型

本文通过对藻类的增长率和基层的吸收率提出有生物意义的表达式,研究了一类具有非线性控制藻类恒花器模型．用定性理论证明了非线性控制可以使变产量的恒化器模型有一个全局渐进稳定的正平衡点．     

赤潮生物种群模型的变结构控制

在已有赤潮理论的基础上,利用细胞接触的抑制作用建立了一个赤潮生物种群的控制模型.根据变结构控制原理,设计变结构控制器,使控制模型在有害藻灭绝时的平衡点处稳定.最后用数值仿真验证所得结果的正确性.     

微生物连续培养模型的最优溢流量控制

本文使用最优控制理论研究了微生物连续培养模型的最优溢流量控制问题,导出了一种关于微生物浓度的线性反馈控制律．在该控制律下,可保证微生物连续培养模型能跟踪理想微生物浓度ｘｄ．     

具有毒素作用和年龄结构的种群模型的最优控制（英文）

本文研究了污染环境下具有年龄结构的三竞争种群的最优控制问题。即讨论了小环境容量下具有年龄结构和毒素作用的种群模型。利用不动点定理研究了该模型解的存在唯一性;采用法锥技巧得到了控制的最优性条件;同时利用Ekeland's变分原理得到了最优控制的存在性。     

多变点模型的检验和估计及其性质

对于可能含有多个变点的模型,本文讨论了关于变点的检验和估计问题,并给出了具体的检验和估计方法．我们还推导了估计的相合性．文中指出即使在总体分布未知的情况下,本文所给的检验和估计仍显示出较好的性质．     

离散广义Logistic模型的混沌控制

利用Lyapunov指数方法,验证了一类离散广义Logistic模型存在混沌现象,并采用混沌控制中OGY方法的基本思想,研究了这类模型的混沌控制问题,得出了消除混沌,保持种群稳定到不动点和2-周期轨道的充分条件．     

几种椎间盘退变动物模型的建立和应用

椎间盘退变是一种年龄相关的退行性疾病,是引起下腰痛的主要因素,严重影响病人的生活质量,并显著增加家庭的经济负担。目前,缺少椎间盘退变的有效干预和治疗手段,部分原因是其发病机制尚未阐明。椎间盘退变动物模型的构建对于阐明该疾病的病理机制至关重要。椎间盘退变是一个复杂的过程,受机械应力、结构损伤、生物化学与基因表达等多种因素的影响。本文总结了应用异常机械应力、结构损伤、生物化学或化学诱导和基因敲除等方式构建的椎间盘退变动物模型。生物力学是维持椎间盘稳态的重要因素,异常的机械应力会导致椎间盘退变。同时,椎间盘退变常伴随结构性损伤,椎间盘结构破坏也会导致椎间盘发生退变。此外,生物化学或化学诱导和关键基因敲除也会导致椎间盘退变。本文按照造成异常机械应力的因素将机械应力模型分为加压模型和失稳模型;按照椎间盘结构将结构损伤模型分为髓核与纤维环损伤模型和软骨终板损伤模型。总结了生物化学或化学诱导模型以及新型的基因敲除模型。讨论了不同类型椎间盘退变动物模型的可能应用和局限性。     

基于后推法的n维Lotka-Volterra竞争模型的稳定化设计

通过后推设计方法,研究一类两两相互竞争的n堆Lotka-Volterra模型的全局稳定化问题．在状态反馈控制下,获得了使闭环系统在正平衡点处全局渐近稳定的控制律．     

The role of structural symmetry in linearizing ocular reflexes

This work presents a simulation study using an anatomically relevant model of the vestibulo-ocular reflex (VOR). The aim is to explore the functional properties of a bilateral structure in the premotor circuits of the oculomotor system. The major conclusions using sinusoidal inputs are: A bilateral structure in a sensory-motor system improves its linear range beyond expected central limits, if provided with symmetric interconnections. Given a bilateral (push-pull) sensory arrangement, non-linear sensor characteristics are actually advantageous. The greatest improvement in linear range of the reflex (here VOR) relies on intact sensors on both sides. In the case of a single sensor (unilateral head velocity input), or unmatched bilateral sensors, this study predicts a decrease in the linear range and the appearance of a variable bias. These implications are compatible with available data and can be tested in a clinical invironment.     

Photoinhibition of photosynthesis in vivo: The role of protein turnover in photosystem II

Divergent theories on the mechanism behind, and the nature of, photoinhibition are discussed, especially in relation to observations made in higher plant leaves. Comparisons are made with 'lower' plant groups and results of in vivo and in vitro experiments are considered. Irradiance-induced mechanisms involved in the regulation of PSII function and structure are discussed in connection with turnover of the DI protein. A model is presented in which a structural change in DI protein facilitates the formation of a population of dissipative PSII centres that do not participate in linear electron transport to PSI. We suggest a sophisticated regulatory mechanism whereby this variable PSII function is controlled with respect to both incident light and biochemical demand, a control which relies on feedback from both light and dark reactions.     

Detection of irregular spatial structures

Wilson et al.'s (1997) study on Glass patterns suggested that the integration of stimulus features into a linear shape occurs quite locally, whereas curved structures--such as circular--require global summation. Their conclusion was based on experiments in which they varied the size of the signal area containing a spatial structure. In the present study, we tested the integration of constant-sized linear and curved Glass patterns by varying their global irregularity. If the mechanisms underlying the detection of a Glass pattern pool features globally throughout the stimulus, the irregularity should have a strong effect on detection performance. The irregular Glass patterns were composed of a variable number of sub-areas, each of which contained its own linear or curved structure. The structural irregularity impaired the detection of the curved patterns, whereas the thresholds for the linear patterns were not affected. Thus, our results are in line with the notion that the integration of curved Glass patterns occurs more globally than the integration of linear patterns.     

A Microcomputer-Based System for Continuous Measurement and Recording Fruit Diameter in Relation to Environmental Factors

A robust yet sensitive field system for continuously measuringand logging diameters of up to eight fruits, together with relevantmeteorological variables such as radiation, temperature andhumidity, is described. The system uses linear variable differentialtransformers to monitor fruit diameter changes and data-loggingis controlled by a microcomputer. A detailed analysis of errorsis presented. Application of the system to the study of environmentalcontrol of diurnal fluctuations in diameter of apple fruitsis described. Key words: Apple, Data logger, LVDTs (linear variable differential transformers)     

Multilayer adaptive control of continuous bioprocesses using optimising control technique. Case study: Bakers' yeast culture

High costs associated with many fermentation processes in an increasingly competitive industry make any prompt application of modern control techniques to industrial bioprocesses very desirable. However, this is often hampered by the lack of adequate mathematical models, on the one hand, and by the absence of continuous, on-line measurement of the most relevant process variables, on the other hand. This paper addresses these problems and offers a new strategy to control continuous bioprocesses using a hierarchical structure such that neither structured process models nor continuous measurement of all relevant variables have to be available. The control system consists of two layers. The lower layer represents a dynamic adaptive follow-up control of a continuously measured output — in our case dissolved oxygen concentration. This variable is supposed to be strongly correlated with the key output variable — in our case cellular concentration which is not continuously available for measurement. The higher layer is then designed to maintain a desired profile of the process key output using a set-point optimising control technique. The Integrated System Optimisation and Parameter Estimation method used operates on an appropriately chosen steady-state performance criterion. A prerequisite for successful application of the proposed approach is an approximate steady-state model, describing the relationship between the measured output and the process key output variable. Furthermore, occasional in situ, off-line or laboratory measurement values of the key output variable are needed. Promising simulation results of the biomass concentration control, by manipulating the air flow-rate in the continuous bakers' yeast culture are presented.     

The control of cell number during central nervous system development in flies and mice

Growth is confined within a size that is normal for each species, revealing that somehow an organism 'knows' when this size has been reached. Within a species, growth is also variable, but despite this, proportion and structure are maintained. Perhaps, the key element in the control of size is the control of cell number. Here we review current knowledge on the mechanisms controlling cell number in the nervous system of vertebrates and flies. During growth, clonal expansion is confined, the number of progeny cells is balanced through the control of cell survival and cell proliferation and excess cells are eliminated by apoptosis. Simultaneously, organ architecture emerges and as neurons become active they also influence growth. The interactive control of cell number provides developmental plasticity to nervous system development. Many findings are common between flies and mice, other aspects have been studied more in one organism than the other and there are also aspects that are unique to either organism. Although cell number control has long been studied in the nervous system, analogous mechanisms are likely to operate during the growth of other organs and organisms.     

基于光投影数字化传感系统的飞蝗表面三维结构

本文基于结构光投影数字化传感系统构建东亚飞蝗Locusta migratoria manilensis表面的三维结构。首先得到其外形尺寸和肢体各部分拓扑结构,然后从被调制的条纹结构光中恢复出物体表面高度变化的相位信息,再通过相位和高度的对应关系重建出物体表面三维特征。此结果将为农药研制和施用设计提供科学依据,对促进蝗虫的防治以及虚拟昆虫研究起到积极作用。     

Germ cells cluster organization in polytrophic ovaries of neuroptera

Histological and ultrastructural analysis of polytrophic ovary structure in Neuroptera revealed an unusual organization of their germ cell clusters. In all species under study (representing 5 families), clusters with variable and unfixed numbers of cystocytes are formed. Moreover, spatial organization of cystocyte connections within the cluster is linear rather than typically branched; only a few branching sites being observed. The oocyte is located in the central, always linear, part of the cluster and therefore is directly connected via intercellular bridges with only two nurse cells. It is postulated here that the linear character of germ cell clusters in Neuroptera may result from asynchrony of cystocyte divisions. Mechanisms of germ cell cluster formation and differentiation are discussed.