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1.
The influence of chemical composition and annealing parameters on the behavior of FeTiP precipitation has been investigated. With increasing Ti content the yield strength and tensile strength were reduced, and the tendency of FeTiP precipitation became more remarkable. No FeTiP precipitate was observed and the best mechanical properties have been obtained in the steel sheet, of which the atom ratio of Ti to N is approximately equal to 1. In the temperature range of 700 to 800℃ the FeTiP precipitation could appear easily. The precipitation process was suppressed when the annealing temperature was below 600℃, and the FeTiP phase was dissolved above 900℃. The FeTiP precipitates would inhibit the migration of grain boundaries during the recrystallization in certain extent, and weaken the density of {111} fiber texture, which resulted in the reduction of r value. The relationship between composition and processing parameters, as well as their influence on the mechanical properties is discussed.  相似文献   

2.
A nonlinear finite element method is applied to observe how inclusion shape influence the thermal response of a ceramic-metal functionally graded material (FGM). The elastic and plastic behaviors of the layers which are two-phase isotropic composites consisting of randomly oriented elastic spheroidal inclusions and a ductile matrix are predicted by a mean field method. The prediction results show that inclusion shape has remarkable influence on the overall behavior of the composite. The consequences of the thermal response analysis of the FGM are that the response is dependent on inclusion shape and its composition profile cooperatively and that the plastic behavior of each layer should be taken into account in optimum design of a ceramic-metal FGM.  相似文献   

3.
A method of extracting and detecting vehicle stability state characteristics based on entropy is proposed. The vehicle’s longitudinal and lateral dynamics models are established for complex driving and maneuver conditions. The corresponding state observer is designed by adopting the moving horizon estimation algorithm, which realizes the observation of the vehicle stability state considering the global state information. Meanwhile, the Shannon entropy is modified to approximate entropy, and the approximate entropy value of the observed vehicle state is calculated. Furthermore, the optimal controller is designed to further validate the reliability of the entropy value as the reference of control system. Simulation results demonstrate that this method can quickly detect the instability state of the system during the process of vehicle driving, which provides a reference for risk prediction and active control.  相似文献   

4.
Behavior-based dual dynamic agent architecture   总被引:1,自引:0,他引:1  
The objective of the architecture is to make agent promptly and adaptively accomplish tasks in the realtime and dynamic environment. The architecture is composed of elementary level behavior layer and high level behavior layer. In the elementary level behavior layer, the reactive architecture is introduced to make agent promptly react to events( in the high level behavior layer, the deliberation architecture is used to enhance the intelligence of the agent. A confidence degree concept is proposed to combine the two layers of the architecture. An agent decision making process is also presented, which is based on the architecture. The results of experiment in RoboSoccer simulation team show that the proposed architecture and the decision process are successful.  相似文献   

5.
Thermo-responsive multiblock polycarbonates were facilely synthesized by covalently binding poly(ethylene glycol)(PEG) and poly(propylene glycol)(PPG) blocks,using triphosgene as coupling agent and pyridine as catalyst.The aqueous solutions of thermo-responsive polycarbonates were investigated by rheological measurements.Steady-state shear measurements reveal that the polycarbonate solutions exhibit shear-thinning behavior and the hydrophilic content has a pronounced effect on the flow behavior of the polycarbonates aqueous solutions.The shear viscosity decreases with increasing poly(ethylene oxide)(PEO) composition.The increase of viscosity with increasing concentration is probably attributed to the formation of stronger network owing to interchain entanglement of PEO block at higher concentration.When the flow curves are fitted to the power law model,flow index is obtained to be less than 1,as exhibiting typical pesudoplastic fluid.The viscoelastic properties of the system also show close dependence on the composition of polycarbonates.Temperature sweep confirms that the multiblock polycarbonates exhibit thermo-responsive properties.For 7% aqueous solution of polycarbonate with composition ratio of EO to PO of 1/1,the sol-gel transition occurs at 37 ℃,which makes the system suitable as an injectable drug delivery system.  相似文献   

6.
Plasma surface alloying of element Nb in TiAl-based alloys and the oxidation behavior were studied. The composition and microstructure of the surface alloyed layers were investigated by means of scanning electron microscopy (SEM),energy dispersive X-ray analysis (EDX),and X-ray diffraction (XRD). The experimental results indicate that the diffusion layers are formed on the TiAl substrate during the plasma niobizing process. The result from oxidation resistance investigation shows that plasma niobizing greatly improves the oxidation resistance of TiAl compared with the untreated TiAl. The role of element Nb for improving the oxidation resistance is considered to be achieved by strengthening the activity of Al,which is induced by the plasma niobizing process.  相似文献   

7.
Parking is an important and indispensable skill for drivers. With rapid urban development, the automatic parking assistant system is one of the key components in future automobiles. Path planning is always essential for solving parking problems. In this paper, a path planning method is proposed for parking using straight lines and circular curves of different radius without collisions with obstacles. The parking process is divided into two steps in which the vehicle reaches the goal state through the intermediate state from the initial state. The intermediate state will be selected from the intermediate state set with a certain criterion in order to avoid obstacles. Similarly, an appropriate goal state will be selected based on the size of the parking lot. In addition, an automatic parking system is built, which effectively achieves the parking lot perception, path planning and performs parking processes in the environment with obstacles. The result of simulations and experiments demonstrates the feasibility and practicality of the proposed method and the automatic parking system.  相似文献   

8.
The knowledge of the equation of state (EOS) and the compressibility of a solid are of central importance for the understanding of the behavior and the application of a condensed matter. The compression behavior of Zr41Ti14Cu12.5Ni10Be22. 5 bulk metallic glass (BMG) is investigated at room temperature up to 24 GPa using in-situ high pressure energy dispersive X-ray diffraction with synchrotron radiation. A model of basic cell volume has been established and the equation of state of BMG is determined by the calculation of radial distribution function. The experimental results indicate that the BMG contains a large amount of vacancy-like free volume. Low pressure ( below 7 GPa) induces the collapse of the free volume to some extent and structure relaxation in the BMG.  相似文献   

9.
A system study of the three-dimensional normal stress for regulating electronic structure and magnetic property of Fe_2Ge is studied. The density states of Fe more than 92% contribution come from Fe 3d,the density states of Ge mainly contributed from Ge 4p and Ge 4s,and the Fe 3d spin induces the Ge 4p electron transfer. The inductive effect increases germanium electron energy,weakens the Fe spin density of states,opposes the stability of the ferromagnetic state. The magnetic moment varies from 5 to 3 μB with the stress charges from-30 to 30 GPa. The charge of Fe is negative whereas the Ge atom is positively charged,the Fe atom loses charge,the charge transfers to the Ge atom. The unevenly distributed charge forms the newoccupy state and spin polarization state in the Fe_2Ge electron structure system. The Fe is the electron donor,the total electron is transferred to Ge,but the total numbers of gain electron and total numbers of lost electron are not equal,so the Fe_2Ge electron system may have hybridization between the Fe 3d state and Ge 4p state.The magnetic of Fe_2Ge mainly comes from the unoccupied Fe 3d orbital,the Fe 3d is positive spinpolarization state and the spin-polarization strength is decreased,the Ge 4p is negative spin-polarization state and the spin-polarization strength are increased. M oreover,electrons-spin polarization is relevant to the structure parameters of the Fe_2Ge system,and controls spin-polarized electronic behavior by means of adjusting ferromagnetic.  相似文献   

10.
The effects of CaO content in the range from 0 to 4.0%, and sintering temperature on the phase composition, relative density and electrical conductivity of 10NiO-NiFe2O4 composites doped with CaO were studied. The results show that there is no change of structure for NiO or NiFe2O4; there is apparent oxygen absorbing and releasing behavior during the heating process in air for 10NiO-NiFe2O4 composites. Introduction of CaO can accelerate the densification of 10NiO-NiFe2O4 composites. The maximum value of relative density is 98.75% for composite doped with 2.0% CaO and sintered at 1 200 ℃, which is beyond about 20% for the undoped composites. The sintering activated energy of sample containing 2% CaO decreases by 15.87 kJ/mol, compared with that of the undoped sample.  相似文献   

11.
系统状态评估是系统可靠性工程中的一个重要课题。针对系统状态评估的一般特点,基于评估对象各项指标和评估基准之间的广义权距离,提出了一种系统状态的评估方法。通过算例可看出,该方法可简便有效地对待评价的同类型多系统状态进行同时评估,克服了传统系统状态评估中的逐一系统评估的繁琐,为系统状态评估提供了一种新方法。  相似文献   

12.
动态系统的状态约束和控制约束等问题可归结为状态空问中某些集合的正不变性,这样系统族的线性状态约束问题为研究系统族的动态行为提供了一条新的途径.本文利用混合单调分解方法来研究离散时滞线性凸多面体系统族的线性状态约束集合的鲁棒正不变性.对由矩阵凸多面体和区间扰动所描述的离散时滞线性时变系统族,得到了鲁棒正不变集的充分必要条件,并给出了证明以及两个推论.且这些条件均由系统族的两个顶点描述,易于检验.  相似文献   

13.
NaCl盐度对活性污泥系统脱氮性能的影响   总被引:8,自引:0,他引:8  
以实际含盐生活污水为处理对象,考察了不同盐度对生物脱氮性能和主导菌群的影响.采用3个平行的序批式生物处理工艺(SBR)在进水(0.17 h)/好氧(7 h)/缺氧(3 h)/沉淀(1.5 h)/排水时间(0.33 h)的运行方式下,在5,7.5,10g/L的盐度下稳定运行50 d左右.结果表明,NaCl盐度对硝化菌的抑制作用远大于反硝化菌,盐度对亚硝酸盐氧化菌群(nitrite oxidation bacteria,简称为NOB)比对氨氧化菌群(ammonia oxidation bacteria,简称为AOB)有更强的抑制作用;7.5和10 g/L系统可以在较短的时间内实现短程硝化反硝化,亚硝酸盐积累率均维持在95%以上.随着盐度的升高,3个系统稳定后的比氨氧化速率逐渐下降;5和7.5 g/L盐度的SBR系统稳定后有较高的氨氮去除率.7.5 g/L盐度可作为普通活性污泥系统实现短程硝化的理想盐度.  相似文献   

14.
为完善基于贝叶斯网络的故障树分析方法,提出了保持贝叶斯网络拓扑结构不变、扩展某些事件节点的状态空间、保持事件节点状态空间不变、调整贝叶斯网络的拓扑结构,两种将存在房形事件的故障树转化为贝叶斯网络的方法.对这两种方法的优劣进行了比较,通过对简化的核电站辅助给水系统的分析,验证了上述方法的正确性.  相似文献   

15.
基于Lyapunov稳定性定理的混沌同步研究与应用   总被引:1,自引:0,他引:1  
非线性动力系统同步的稳定性一般由条件Lyapunov指数来决定,文中提出了一种简捷确定两个同构的系统稳定性的方法,主要是通过判定两个同构系统的误差渐近稳定性来确定,这样就避免繁琐计算Lyapunov指数.将该设计方法应用于两个Lorenz系统同步,仿真结果表明,该方法方便可行,有效地实现了混沌同步控制,并通过加密语音文件实例来证明该方案具有较好的同步特性和较高的安全性.  相似文献   

16.
小型航天器浸入与不变自适应反步姿态跟踪   总被引:1,自引:0,他引:1       下载免费PDF全文
针对具有惯性张量不确定性、外干扰及饱和限制的小型航天器非线性姿态跟踪问题,将反步法和系统浸入与流形不变理论相结合,提出了分块自适应约束控制结构.航天器姿态模型由修正罗德里格参数进行全局非奇异描述.在设计反步控制器时,引入指令滤波器和修正跟踪误差信号以施加系统状态和执行器的饱和限制,同时较容易地获得虚拟控制导数.为提高反步控制器的鲁棒性和性能,利用基于不变流形的非线性观测器对时变的系统“总干扰”进行在线估计补偿.由于不变流形方法使得估计误差具有指定的一致稳定动态,因而该分块自适应控制器比传统的自适应反步控制器更容易调节,且性能不受未知的估计律动态的影响.李亚普诺夫直接方法证明了估计误差有界性和闭环系统输入状态稳定.数值仿真表明,与传统方法相比,所提出的控制器结构具有更高的姿态跟踪性能和干扰估计精度.  相似文献   

17.
单模光纤偏振度的不变性研究   总被引:1,自引:0,他引:1  
高速、长距离光纤传输中,偏振模色散(PMD)成为影响传输质量的主要障碍之一,必须进行补偿。在偏振模色散补偿时,采用哪个量,直接影响着补偿的效果和实现的可能,本文旨在研究光纤传输中偏振态的偏振度不变性,从而为补偿提供可靠的理论依据。  相似文献   

18.
提出一种满足协同虚拟环境系统协同操作要求的一致性控制技术.给出协同虚拟环境系统的一致性定义,分析了传统网络虚拟环境系统所采用一致性控制方法不能用于协同虚拟环境系统的原因.对系统同步所有节点物理时钟,通过本地滞后技术进行一致性控制,当由于过大的网络传输延迟产生不一致状态时,通过时间扭曲机制进行状态修复.实验结果表明,在不同网络负载下,该技术均能支持多个用户同时对一个对象进行协同操作.  相似文献   

19.
Petri网是一种适于系统描述、分析和综合的图形数学工具,它的研究已引起了人们的普遍关注。本文着重讨论了一般Petri网理论,并对计时、随机和高级Petri网以及Petri网理论的应用进行了简要的介绍。  相似文献   

20.
利用前向网络输入元素非线关联的方法实现了从输入模式空间到输出标识空间复杂的非线性变换。推导了学习方法,并在学习过程把模式的平稳不变识别、比例不变识别及旋转不变识等条件构造在神经网络的权结构之中,使其具有模式不变识别能力,同时借助等权类的概念,极大地简化了网络的拓扑结构,降低了学习时间。  相似文献   

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