Physics-Informed Multistage Machine Learning Strategy for the Nanomachining-Induced Plastic Deformation Behavior

The evolution of the dislocation density induced by the nanomachining process dominates the plastic deformation behaviors of materials, thus affecting the mechanical properties significantly. However, a challenging topic related to how to establish an accurate model for predicting the dislocation density based on the limited simulations and experiments arises due to the complicated thermal–mechanical coupling mechanism during the machining process. Herein, a multistage method integrating machine learning, physics, and high-throughput atomic simulation is proposed to investigate the effect of cutting speed on the dislocation behavior in polycrystal copper. Compared with the traditional one-step machine learning method, the constraint of physical features effectively improves the accuracy and generalization ability of the model. The results indicate that the dislocation behaviors depend on the competition between the cutting force and temperature. In the low-cutting speed, the predominated role of the cutting temperature leads to a rapid decline of the dislocation density. In contrast, the dislocation density tends to be stable under a high-speed cutting process due to the dynamic balance between the effects of the cutting force and temperature. Notably, the proposed strategy provides a new and universal framework to design the machining parameters to obtain high-quality products.     

A Flexible Conformal Piezoresistive Sensor Based on Electrospinning for Deformation Monitoring of Carbon Fiber-Reinforced Polymer

Carbon fiber-reinforced polymer (CFRP) materials are widely applied in various areas as key structure components. The structural health monitoring of the CFRP components is crucial to prevent catastrophic failure. However, the nonplane surfaces of CFRP components hinder the attaching of monitoring sensors with hard substrates. Therefore, the substrate conditions for sensor preparation are mainly considered in this study. To adapt the proposed sensors to the curved substrate, including nondevelopable surfaces, electrospinning method is used to prepare conformal piezoresistive fiber films, in which polymethyl methacrylate is served as the matrix and carbon nanotubes are utilized as the conductive filler. The piezoresistive fibers covered on CFRP substrates have a gauge factor up to 207.95 and can response to the strain less than 0.05%. Moreover, the sensor also has high durability and the ability to follow the dynamic excitation signals with as high as 50 Hz.     

Engineered Macrophages: A Safe-by-Design Approach for the Tumor Targeting Delivery of Sub-5 nm Gold Nanoparticles

Ultrasmall nanoparticles (NPs) are a promising platform for the diagnosis and therapy of cancer, but the particles in sizes as small as several nanometers have an ability to translocate across biological barriers, which may bring unpredictable health risks. Therefore, it is essential to develop workable cell-based tools that can deliver ultrasmall NPs to the tumor in a safer manner. Here, this work uses macrophages as a shuttle to deliver sub-5 nm PEGylated gold (Au) NPs to tumors actively or passively, while reducing the accumulation of Au NPs in the brain. This work demonstrates that sub-5 nm Au NPs can be rapidly exocytosed from live macrophages, reaching 45.6% within 24 h, resulting in a labile Au NP-macrophage system that may release free Au NPs into the blood circulation in vivo. To overcome this shortcoming, two straightforward methods are used to engineer macrophages to obtain “half-dead” and “dead” macrophages. Although the efficiency of engineered macrophages for delivering sub-5 nm Au NPs to tumors is 2.2–3.8% lower than that of free Au NPs via the passive enhanced permeability and retention effect, this safe-by-design approach can dramatically reduce the accumulation of Au NPs in the brain by more than one order of magnitude. These promising approaches offer an opportunity to expand the immune cell- or stem cell-mediated delivery of ultrasmall NPs for the diagnosis and therapy of diseases in a safer way in the future.     

环肋圆柱壳在流场中的辐射声压

应用Ｈｕｙｇｅｎｓ原理和Ｇｒｅｅｎ函数方法推出了环肋圆柱壳在流场中辐射声场压力的积分公式,可用来计算壳体表面、近场和远场的声压。     

影响涂料印花增稠剂增稠及抗渗化性能的因素

讨论了反乳液聚合法合成涂料印花增稠剂时,影响聚合产物的抗渗化性能及增稠效果的主要因素。研究发现,提高聚合温度可以提高聚合产物的抗渗化性,但配制高粘度印花浆时对增稠效果不利,而在配制低粘度印花浆时则反之。降低交联单体用量有利于提高聚合产物的抗渗化性,并可提高聚合产物在配制较低粘度印花浆时的增稠效果。     

Steady-state limiting currents determined by coupled diffusion, migration, and chemical equilibrium

A simple theoretical model is presented for the reduction of a singly charged cation under conditions where migration is important and the cation is coupled to a neutral species through a chemical equilibrium, AB = A(+) + B(-). Only the steady-state transport-limited current, I(l), is considered. Simple algebraic equations describe the ratio of I(l) to the diffusion-limited current, I(d), as it depends on the degree of dissociation, determined by the ratio of equilibrium constant to formal concentration, K(AB)/C*(AB). The ratio I(l)/I(d) is found to depend on the ratio of electrolyte to equilibrium concentration of A(+) in bulk solution just as for the well-known result for the case without the equilibrium (i.e., K(AB) → ∞). The results are in accord with published experimental data for weak acids. Agreement and disagreement with other theoretical treatments of this problem are discussed. The main results are for 1:1 supporting electrolytes; extensions are made to 2:1, 1:2, and 2:2 supporting electrolytes.     

Three-map absolute moiré contouring

In the shadow-moiré system, the period of the grating is varied by rotation of the grating, so the phase of the moiré pattern is changed as well. By the selection of suitable rotation angles, three images at different positions of the grating are acquired to obtain the absolute distance from the object to the grating. A theoretical analysis is presented for the method, and some experiments have been done to verify the theoretical analysis. The results show that the method is fast and the accuracy is better than 10 μm. The measurable range is directly proportional to the period of the grating and inversely proportional to the angles at which the grating is rotated.     

Adaptive control of harmonic drive with parameter varying friction using structurally dynamic wavelet network

In this paper, an adaptive controller with structurally dynamic wavelet network is developed for a harmonic drive subject to parameter varying friction. The control architecture integrates a proportional controller, a feedback adaptive component and sliding component to adaptively compensate for the friction to achieve accurate position tracking. Global asymptotic stability of the algorithm is proved by using Lyapunov function. In parallel to the adaptive controller, a fuzzy reconfiguration scheme is devised to change the structure of the network along with weights updating to improve the system tracking performance and robustness. Experimental tests on a harmonic drive manipulator verify the effectiveness of the proposed control method.     

自动测试系统中的仪器设备驱动通用封装研究

在目前的自动测试系统软件开发中,虚拟仪器设备指令的非通用性会导致系统开发繁琐、无法集成等问题,针对这些问题提出了一种适合大部分仪器设备的封装方法;这种封装方法,通过动态链接库的形式将事件处理机制嵌入到仪器驱动封装里,拥有跨平台、适用面广、开发速度快和仪器可互换等特点;经过在实际雷达射频模块自动测试系统项目中的应用,结果表明该方法能够实现跨平台操作、具有仪器互换和封装简便等特点,并且表现出极强的通用性,具有一定的实用性和推广价值.     

Coordination of discrete‐time multi‐agent systems via relative output feedback

This paper investigates the joint effects of agent dynamic and network topology on the consensusability of linear discrete‐time multi‐agent systems via relative output feedback. An observer‐based distributed control protocol is proposed. A necessary and sufficient condition for consensusability under this control protocol is given, which explicitly reveals how the intrinsic entropy rate of the agent dynamic and the eigenratio of the undirected communication graph affect consensusability. As a special case, multi‐agent systems with discrete‐time double integrator dynamics are discussed where a simple control protocol directly using two‐step relative position feedback is provided to reach a consensus. Finally, the result is extended to solve the formation and formation‐based tracking problems. The theoretical results are illustrated by simulations. Copyright © 2010 John Wiley & Sons, Ltd.