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The paper proposes a model-based nonlinear model predictive control (NMPC) method for online control of crystal mean size and standard deviation in cooling crystallization process. Image analysis method using deep learning neural network and mathematical statistical method are performed to obtain the mean size and standard deviation of crystal population. The nonlinear prediction model for the NMPC is derived from the input and output data. The effectiveness of the proposed NMPC method is evaluated by the alum cooling crystallization experiments. Experimental results demonstrate the benefits of the proposed combination of image analysis and feedback control of the crystal mean size and standard deviation. The control performance of NMPC is superior to model-free path following control (PFC) method due to the prediction and optimization capabilities of NMPC. • Model-based nonlinear model predictive control for crystal mean size and standard deviation. • Model-free path following control for crystal mean size and standard deviation. • Image analysis method using deep learning to obtain pixel-level instance segmentation. • The effectiveness of the proposed control methods is evaluated by the alum cooling crystallization experiments. [ABSTRACT FROM AUTHOR]

This paper proposes the energy-based controller (EC) incorporated with radical basis function (RBF) neural-network compensation (ECRBFC), which is used to swing up the Pendubot and raise it to its uppermost unstable equilibrium position. First, for the known dynamics model of the two-link arm, the EC is designed. In the EC, the singularity is successfully avoided by constructing an appropriate energy evaluation function. Second, as for the friction of the Pendubot, because of the time-varying characteristics, an accurate friction dynamics model cannot be known absolutely; thus, the RBF neural network is introduced to offset the bad effect of friction. Finally, in order to evaluate the performance of ECRBFC, the numerical simulations and the experimental results are given, and by comparing the results with that of other algorithms, it is found that ECRBFC proposed in this paper has better performance under the same conditions. [ABSTRACT FROM PUBLISHER]

Abstract: We report the exploration of Ge2Sb2Te5 (GST) chemical mechanical polishing (CMP) mechanism. Static etching experiments of GST film were first conducted in two typical silica-based slurries (pH 2 and pH 11). To investigate the chemical nature of GST in different chemical environments, solubility of GST in slurries and also the zeta potentials of GST powders vs pH were measured. We further compared the polishing performance to the removal rate (RR), surface roughness, polishing selectivity of GST over oxide, and influence on the phase change property by using the two typical slurries. Then measurements were done for the hardness of GST films before and after polishing, particle size of the slurry during polishing, and also the open circuit potential (OCP) of GST in the two slurries. On the basis of the aforementioned results, we proposed a possible mechanism for GST CMP including reaction formulas, removal of GST as molecules instead of as a lump, surface hydration in alkaline region and electrochemical process, which was partially supported by residue analysis for 8″ patterned wafers using energy dispersive spectroscopy (EDS) under transmission electron microscope (TEM). [Copyright &y& Elsevier]

Abstract: It was found material removal rate (MRR) sharply increased from 250 to 675nm/min as the concentration decreased from 1 to 0.25wt% in optical glass chemical mechanical polishing (CMP) using ceria slurries. Scanning electron microscopy was employed to characterize the ceria abrasive used in the slurry. Atomic force microscopy results showed good surface had been got after CMP. Schematic diagrams of the CMP process were shown. Furthermore, the absorption spectra indicated a sudden change from Ce4+ to Ce3+ of the ceria surface when the concentration decreased, which revealed a quantum origin of the phenomenon. [Copyright &y& Elsevier]

To perform power augmentation tasks of a robotic exoskeleton, this paper utilizes fuzzy approximation and designed disturbance observers to compensate for the disturbance torques caused by unknown input saturation, fuzzy approximation errors, viscous friction, gravity, and payloads. The proposed adaptive fuzzy control with updated parameters' mechanism and additional torque inputs by using the disturbance observers are exerted into the robotic exoskeleton via feedforward loops to counteract to the disturbances. Through such an approach, the system does not need any requirement of built-in torque sensing units. In order to validate the proposed framework, extensive experiments are conducted on the upper limb exoskeleton using the state feedback and output feedback control to illustrate the performance of the proposed approaches. [ABSTRACT FROM PUBLISHER]

The influence of polyvinyl alcohol (PVA) and polyacrylamide (PAM) on the stability of acidic colloidal silica in aqueous environment was examined. Experiments were carried out on the original colloidal silica (CS), PVA modification and PAM modification. PVA- and PAM-modified CS could remain stable for 20 and 13 days in the oven under 50 °C; however, nonmodified CS is only stable for 9 days. The thermal stability of CS was significantly improved through PVA modification. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results show that the modified particles reveal better dispersibility. The action mechanism between polymer and CS was studied by particle size distribution, zeta potential, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR). The results show that the modified silica particles acquire more negative charge and the interactions among silica particles and PVA are stronger than among silica particles and PAM. Such differences appeared to be due to the loss of water molecules between C-OH of PVA and Si-OH bonds, which form a dense monomolecular adsorbed layer on the surface of the silica particles, thus increasing space steric repulsion. However, for the situation of PAM, the interaction was weakened. The results provided important basis to optimize stability of acidic CS in the aqueous environment. [ABSTRACT FROM AUTHOR]

This article proposes a novel robust swing-up and balance control method using data-driven compensation signals for the Pendubot system, which is underactuated and subject to dynamic friction, backlash, and modeling uncertainty. The method involves three major developments. First, the uncertainty of the system is described by a previous sampled unknown nonlinear term and its changing rate. Compensation signals are then designed to eliminate the influence of the previous sampled unknown nonlinear term and its changing rate on the outputs of the controlled plant. Second, based on the Lyapunov stability theory, a robust swing-up control method is proposed. Third, in order to eliminate the limit cycle phenomenon caused by the uncertainty near the unstable equilibrium point, a proportional-derivative balance controller based on compensation signals is proposed. The stability and tracking error analysis show that the compensation signals can effectively eliminate the influence of dynamic friction, backlash, and modeling uncertainty on the system. Experimental results verify the effectiveness of the proposed method by showing significant improvements in production rate, accuracy, and cost. [ABSTRACT FROM AUTHOR]

The effect of oxidation temperature on interfacial properties of n -type 4H-SiC metal-oxide-semiconductor capacitors has been systematically investigated. Thermal dry oxidation process with three different oxidation temperatures 1200 °C, 1300 °C and 1350 °C were employed to grow SiO 2 dielectric, following by the standard post-oxidation annealing (POA) in NO ambience at 1175 °C for 2 h. The root mean square (RMS) roughness measured by Atomic Force Microscopy for the thermally grown SiO 2 before POA process is reduced with increasing the oxidation temperature, obtaining an atomically flat surface with a RMS of 0.157 nm from the sample oxidized at 1350 °C. Several kinds of electrical measurements were used to evaluate the densities of near interface traps and effective fixed dielectric charge for the samples, exhibiting a trend reduced with increasing the oxidation temperature. The interface state density of 3 × 10 11 cm −2 eV −1 at 0.2 eV from the conduction band edge was achieved from conductance method measurement for the sample oxidized at 1350 °C. The results from Secondary Ion Mass Spectroscopy and X-ray Photoelectron Spectroscopy demonstrate that high oxidation temperature can reduce the width of transition layer, the excess Si and silicon suboxide compositions near the interface, leading to effective improvement of the interfacial properties. [ABSTRACT FROM AUTHOR]

Highlights: [•] CMP process of 12in. GST blank wafer and pattern wafer with 60nm width damascene trenches in the acidic slurry. [•] Successfully EPD technique of GST CMP process using optical methods. [•] It has a little difference of EPD curve between blank wafer and pattern wafer. The EPD curve of pattern curve can divide into four stages. [•] Average dishing of GST are less than 3.5nm and the wafer-to-wafer variation is less than 8.0%. [•] A reproducible result is obtained using EPD technique although large variation of RR. [Copyright &y& Elsevier]

• High performance 4H-SiC TJBS has been successfully designed and fabricated. • The optimal design is verified by the experimental results. • The FOM of TJBS is improved by 56.3% when compared with that of the PJBS. In this paper, high performance 4H-SiC trench junction barrier Schottky diodes (TJBS) have been successfully designed and fabricated. For making a larger design window that enables good reverse blocking and forward conduction capabilities at the same time in TJBS, trench profile, especially bevel angle (θ) of a tapered trench sidewall, are further studied. The optimal design is verified by the experimental results measured from the fabricated 4H-SiC JBS and TJBS diodes. Experimental results show that the reverse leakage current (I r) of the TJBS is only 1.62 × 10−7 A/cm2 at Vr of 1200 V, which is about one order of magnitude less than that of planar JBS (PJBS) fabricated at the same time. The figure of merit (FOM) of TJBS is improved by 56.3% when compared with that of the PJBS. [ABSTRACT FROM AUTHOR]