柔性制造系统非阻塞监督控制器优化设计

针对一类含有并发执行装配过程的柔性制造系统G-systems,提出一种新的死锁预防策略保证该系统的非阻塞性,即在控制下,受控系统从任意可达状态都可以到达理想状态.首先对Petri网模型中基本信标实施控制,保证了基本信标的最大可控,然后通过线性规划算法求取所有从属信标满足可控性的条件,即获得基本信标的控制深度变量.与现有方法相比,该策略优点在于只需加入少量的控制库所,就可避免不必要的迭代过程;其次是提出控制器输出弧位置优化策略,得到了结构更为简单、许可行为更多的非阻塞Petri网控制器.     

On Generalized Fuzzy Belief Functions in Infinite Spaces

Determined by a fuzzy implication operator, a general type of fuzzy belief structure and its induced dual pair of fuzzy belief and plausibility functions in infinite universes of discourse are first defined. Relationship between the belief-structure-based and the belief-space-based fuzzy Dempster-Shafer models is then established. It is shown that the lower and upper fuzzy probabilities induced by the fuzzy belief space yield a dual pair of fuzzy belief and plausibility functions. For any fuzzy belief structure, there must exist a fuzzy belief space such that the fuzzy belief and plausibility functions defined by the given fuzzy belief structure are just the lower and upper fuzzy probabilities induced by the fuzzy belief space, respectively. Essential properties of the fuzzy belief and plausibility functions are also examined. The fuzzy belief and plausibility functions are, respectively, a fuzzy monotone Choquet capacity and a fuzzy alternating Choquet capacity of infinite order.     

地磁场在缺陷微磁检测中的作用分析

地磁场在缺陷微磁检测中的作用是实现微磁检测定量化的理论基础;通过微磁学理论分析地磁场反复磁化铁磁性物质的物理过程,由于磁畴壁的移动,在缺陷区产生固定磁畴结点,固定磁畴结点内的磁场在缺陷处发生泄漏,形成可识别的缺陷信号,固定磁畴结点一旦产生其磁场强度远大于地磁场,地磁场对缺陷微磁检测的影响只会改变检测信号的幅值,不会改变缺陷信号的特征,揭示了缺陷磁场失而复得的原因,同时实验验证了地磁场在应力致磁效应中起到偏置磁场的作用,为在役设备微磁检测奠定了理论基础。     

基于组织结构的纺织品各向异性建模方法

纺织面料的物理仿真将虚拟现实与纺织CAD相结合,是虚拟服装与试衣系统研究的一项关键技术,纺织品建模也是纺织品真实感模拟的基础及关键工作.在基于物理的粒子系统的基础上,提出各向异性的建模方式.根据织物面料的不同组织方式进行分析,对其进行经纬方向的分离建模.仿真过程分为初始过程的刚性物体模拟和接近平衡时的柔性物质模拟两大步骤.为了在产生逼真表现效果的同时兼顾计算复杂性,构模时引入多分辨率模型.     

基于 CEEMDAN 与改进核极限学习机的S700K 转辙机健康状态诊断

针对S700K转辙机健康状态分类过于粗放、诊断速度慢、效率低的问题,提出一种基于CEEMDAN与改进核极限学习机(kernel based extreme learning machine, KELM)的诊断方法。首先,对S700K转辙机功率数据进行自适应噪声完备集合经验模态分解,得到6个本征模态函数(intrinsic mode function, IMF);然后,计算本征模态函数的模糊熵值(fuzzy entropy, fuzzyEn, FE)作为表征转辙机健康状态的特征参数;最后,利用麻雀算法(sparrow search algorithm, SSA)改进的核极限学习机对9种健康状态进行健康诊断,并与SVR和ELM模型进行对比。仿真结果表明,改进核极限学机模型准确率、精确率、召回率等指标分别达到97.8%、98.0%、97.8%,相较于SVR和ELM模型,SSA-KELM模型在保证运行速度的基础上,将诊断准确率至少提高2.2%。     

基于偏振不敏感超材料的全光可调谐太赫兹慢光效应研究

太赫兹(terahertz,THz) 慢光效应可以有效地提升THz脉冲数据传输的安全性和存储性,而一般THz慢光器件对入射THz波偏振态变化敏感。本文设计了一种超材料结构,其微结构单元由一个十字型谐振器和4个U型谐振器构成。研究表明:基于超材料的THz慢光效应对线偏振光和圆偏振光均不敏感。通过对超材料结构的参数优化,获得到了最大群折射率为1 618的慢光效应。另外,本文在超材料微结构层和SiO₂衬底之间嵌入了一层二硫化钼(MoS₂)薄膜,当MoS₂的载流子浓度从1.7×10¹⁷ cm-3增大到5.1×10¹⁹ cm-3时,群折射率从1 566减小到26。实现了偏振不敏感全光可调谐的THz慢光效应。该研究有望为偏振不敏感和全光可调谐的THz慢光器件设计提供崭新的研究思路。     

Photomultiplication-Type Organic Photodetectors with High EQE-Bandwidth Product by Introducing a Perovskite Quantum Dot Interlayer

A photomultiplication (PM)-type organic photodetector (OPD) that exploits the ionic motion in CsPbI₃ perovskite quantum dots (QDs) is demonstrated. The device uses a QD monolayer as a PM-inducing interlayer and a donor–acceptor bulk heterojunction (BHJ) layer as a photoactive layer. When the device is illuminated, negative ions in the CsPbI₃ QD migrate and accumulate near the interface between the QDs and the electrode; these processes induce hole injection from the electrode and yield the PM phenomenon with an external quantum efficiency (EQE) >2000% at a 3 V applied bias. It is confirmed that the ionic motion of the CsPbI₃ QDs can induce a shift in the work function of the QD/electrode interface and that the dynamics of ionic motion determines the response speed of the device. The PM OPD showed a large EQE-bandwidth product >10⁶ Hz with a −3 dB frequency of 125 kHz at 3 V, which is one of the highest response speeds reported for a PM OPD. The PM-inducing strategy that exploits ionic motion of the interlayer is a potential approach to achieving high-efficiency PM OPDs.     

Plasmon-Assisted Self-Encrypted All-Optical Memory

All-optical responsive nanomaterials, which can rapidly switch between two stable states, have been regarded as the next-generation memories due to their potential to realize binary information storage and implement on-chip, integrated photonic neuromorphic systems. Rare earth oxides are preeminent candidates owing to their extraordinary luminescent stability and narrow optical transitions. However, due to the lack of simple and effective optical switches, it is difficult to realize all-optical data storage, encoding, and retrieval by pure rare earth-doped luminescent nanoparticles. Here, a rapid and high-contrast of 10⁴ luminescent switching of Y₂O₃:Eu³⁺ nanoparticle between the enhancement and quenching states is achieved by employing the strong light confinement and ultrafast thermal response of localized surface plasmon resonance. A self-encrypted all-optical memory is presented with optical information writing, encryption, reading, and re-writing, and a high-sensitivity synaptic response of emitters to frequency and light intensity flux, which can be harnessed to encrypt information flows and promote convenient and high-security information encryption. Such a convenient and secure plasmonic thermally assisted self-encrypting luminescent switch paves the way for constructing high-performance stimuli-responsive rare earth oxide crystals on demand and expanding their applications in various data encryption, anti-counterfeiting, and rewritable colouration devices.     

霍尔效应传感器设计

霍尔效应传感器广泛用于识别电机定、转子之间相对位置,实现电机的电子换相。目前,大多数论述是描述霍尔特性及其在BLDC电机的应用工作原理,对电机效应霍尔传感器的设计没有完整的阐述。基于Saber 仿真,文中对三相BLDC工作逻辑分析,建立霍尔效应传感器数学模型。结合霍尔感应区尺寸得出与识别精度有关的条件关系式;详细阐述霍尔效应传感器的安装分布、布局、霍尔类型及特点、印制板电路等设计要点。其结果有利于缩小传感器占用空间尺寸,对于电机霍尔效应传感器及运动位置识别传感器的设计,具有理论意义和现实价值。     

Diagnostic performance of edited 2HG MR spectroscopy of central glioma in the clinical environment

Magnetic Resonance Materials in Physics, Biology and Medicine - Oncometabolite D-2-hydroxyglutarate (2HG) is pooled in isocitrate dehydrogenase (IDH)-mutant glioma cells. Detecting 2HG by MR...