Identification and U-control of a state-space system with time-delay

This article presents a state-space model with time-delay to map the relationship between known input-output data for discrete systems. For the given input-output data, a model identification algorithm combining parameter estimation and state estimation is proposed in line with the causality constraints. Consequently, this article proposes a least squares parameter estimation algorithm, and analyzes its convergence for the studied systems to prove that the parameter estimation errors converge to zero under the persistent excitation conditions. In control system design, the U-model based control is introduced to provide a unilateral platform to improve the design efficiency and generality. A simulation portfolio from modeling to control is provided with computational experiments to validate the derived results.     

Pressure-induced transparency of MgO,Al2O3, AlN,and cBN ceramics at room temperature

The in situ axial X-ray diffraction patterns of four ceramic powder samples (MgO, Al₂O₃, AlN, and cBN) that were compressed in a diamond anvil cell under uniaxial non-hydrostatic conditions were recorded. The microscopic deviatoric stress as a function of the pressure was determined from the X-ray diffraction peak broadening analysis: the curves increased approximately linearly with the pressure at the initial compression stage and then levelled off under further compression. Pressure-induced transparency was observed in all of the samples under compression, and the pressure at the turning point on the curves of the microscopic deviatoric stress versus pressure corresponded to the pressure at which the samples became transparent. Analysis of the microstructural features of the pressure-induced transparent samples indicated that the compression caused the grains to fracture, and the broken grains bonded with each other. We demonstrated that the ceramics’ pressure-induced transparency was a process during which the grains were squeezed and broken, the pores were close between the grains, and the broken grains were re-bonded under compression.     

Statistical Piezotronic Effect in Nanocrystal Bulk by Anisotropic Geometry Control

Utilizing inner-crystal piezoelectric polarization charges to control carrier transport across a metal-semiconductor or semiconductor–semiconductor interface, piezotronic effect has great potential applications in smart micro/nano-electromechanical system (MEMS/NEMS), human-machine interfacing, and nanorobotics. However, current research on piezotronics has mainly focused on systems with only one or rather limited interfaces. Here, the statistical piezotronic effect is reported in ZnO bulk composited of nanoplatelets, of which the strain/stress-induced piezo-potential at the crystals’ interfaces can effectively gate the electrical transport of ZnO bulk. It is a statistical phenomenon of piezotronic modification of large numbers of interfaces, and the crystal orientation of inner ZnO nanoplatelets strongly influence the transport property of ZnO bulk. With optimum preferred orientation of ZnO nanoplatelets, the bulk exhibits an increased conductivity with decreasing stress at a high pressure range of 200–400 MPa, which has not been observed previously in bulk. A maximum sensitivity of 1.149 µS m⁻¹ MPa⁻¹ and a corresponding gauge factor of 467–589 have been achieved. As a statistical phenomenon of many piezotronic interfaces modulation, the proposed statistical piezotronic effect extends the connotation of piezotronics and promotes its practical applications in intelligent sensing.     

Synergistic effect of bulk phase doping and layered-spinel structure formation on improving electrochemical performance of Li-Rich cathode material

In this study, La was doped into the lithium layer of Li-rich cathode material and formed a layered-spinel hetero-structure. The morphology, crystal structure, element valence and kinetics of lithium ion migration were studied by field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The La doped lithium-rich cathode material exhibited similar initial discharge capacity of 262.8 mAh g^?1 at 0.1 C compared with the undoped material, but the discharge capacity retention rate can be obviously improved to 90% after 50 cycles at 1.0 C. Besides that, much better rate capability and Li⁺ diffusion coefficient were observed. The results revealed that La doping not only stabilized the material structure and reduced the Li/Ni mixing degree, but also induced the generation of spinel phase to provide three-dimensional diffusion channels for lithium ion migration. Moreover, the porous structure of the doped samples also contributed to the remarkable excellent electrochemical performance. All of these factors combined to significantly improve the electrochemical performance of the material.     

Novel TiC-based composites with enhanced mechanical properties

Novel TiC-based composites were synthesized by reactive hot-pressing at 1800 °C for 1 h with ZrB₂ addition as a sintering aid for the first time. The effects of ZrB₂ contents on the phase composition, microstructure evolution, and mechanical properties were reported. Based on the reaction and solid solution coupling effects between ZrB₂ and TiC, the product ZrC may be partially or completely dissolved into the TiC matrix, and then phase separation within the miscibility gap is observed to form lamellar nanostructured ZrC-rich (Zr, Ti)C. The TiC-10 mol.% ZrB₂ (starting batch composition) exhibits good comprehensive mechanical properties of hardness 27.7 ± 1.3 GPa, flexural strength 659 ± 48 MPa, and fracture toughness of 6.5 ± 0.6 MPa m^1/2, respectively, which reach or exceed most TiC-based composites using ceramics as sintering aids in the previous reports.     

Mechanical Properties of Single-Layer Diamond Reinforced Poly(vinyl alcohol) Nanocomposites through Atomistic Simulation

Low-dimensional carbon nanostructures are ideal nanofillers to reinforce the mechanical performance of polymer nanocomposites due to their excellent mechanical properties. Through molecular dynamics simulations, the mechanical performance of poly(vinyl alchohol) (PVA) nanocomposites reinforced with a single-layer diamond – diamane is investigated. It is found the PVA/diamane exhibits similar interfacial strengths and pull-out characteristics with the PVA/bilayer-graphene counterpart. Specifically, when the nanofiller is fully embedded in the nanocomposite, it is unable to deform simultaneously with the PVA matrix due to the weak interfacial load transfer efficiency, thus the enhancement effect is not significant. In comparison, diamane can effectively promote the tensile properties of the nanocomposite when it has a laminated structure as it deforms simultaneously with the matrix. With this configuration, the interlayer sp³ bonds endows diamane with a much higher resistance under compression and shear tests, thus the nanocomposite can reach very high compressive and shear stress. Overall, enhancement on the mechanical interlocking at the interface as triggered by surface functionalization is only effective for the fully embedded nanofiller. This work provides a fundamental understanding of the mechanical properties of PVA nanocomposites reinforced by diamane, which can shed lights on the design and preparation of next generation high-performance nanocomposites.     

Prevention of breast cancer by dietary polyphenols—role of cancer stem cells

Abstract

Breast cancer is a common malignancy with poor prognosis. Cancer cells are heterogeneous and cancer stem cells (CSCs) are primarily responsible for tumor relapse, treatment-resistance and metastasis, so for breast cancer stem cells (BCSCs). Diets are known to be associated with carcinogenesis. Food-derived polyphenols are able to attenuate the formation and virulence of BCSCs, implying that these compounds and their analogs might be promising agents for preventing breast cancer. In the present review, we summarized the origin and surface markers of BCSCs and possible mechanisms responsible for the inhibitory effects of polyphenols on BCSCs. The suppressive effects of common dietary polyphenols against BCSCs, such as curcumin, epigallocatechin gallate (EGCG) and related polyphenolic compounds were further discussed.     

A mini review on two-dimensional nanomaterial assembly

Two-dimensional (2D) nanomaterials have attracted a great deal of attention since the discovery of graphene in 2004, due to their intriguing physicochemical properties and wide-ranging applications in catalysis, energy-related devices, electronics and optoelectronics. To maximize the potential of 2D nanomaterials for their technological applications, controlled assembly of 2D nanobulding blocks into integrated systems is critically needed. This mini review summarizes the reported strategies of 2D materials-based assembly into integrated functional nanostructures, from in-situ assembly method to post-synthesis assembly. The applications of 2D assembled integrated structures are also covered, especially in the areas of energy, electronics and sensing, and we conclude with discussion on the remaining challenges and potential directions in this emerging field.