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Metalorganic chemical vapor deposition (MOCVD) was used to grow crystalline GaN on a Ga2O3 interlayer deposited by pulsed laser deposition. The Ga2O3 interlayer situated between undoped GaN (u-GaN) and sapphire can be etched out during the chemical lift-off process. A (2-01) oriented β-Ga2O3 thin film was first deposited on the sapphire; this was followed by u-GaN growth via MOCVD carried out in an N2 atmosphere to prevent the decomposition of Ga2O3. Using transmission electron microscopy (TEM), the orientation relationship was observed to be GaN[112-0]?Ga2O3[010] where the lattice mismatch between the two materials was 8.5%. The full width at half maximums of the x-ray rocking curve at the GaN (0002) plane and of the photoluminescence spectrum measured from GaN/Ga2O3/sapphire were 1444 arcsec and 8.3 nm, respectively; these were almost identical to the measured values for GaN/sapphire fabricated in an N2 environment. It was concluded that the growth atmosphere played a more important role in determining the crystallinity of u-GaN than the Ga2O3 thin film underneath. Finally, an InGaN light-emitting diode structure was successfully fabricated on the GaN/Ga2O3/sapphire. [ABSTRACT FROM AUTHOR]

Abstract: Epoxy/LiAl layered double hydroxides (LDH) nanocomposites have been synthesized from organic polymer (epoxy) and two-dimensional host materials (LiAl LDHs) by in situ cross-linking polymerization reaction. LiAl LDHs have unique properties like high anionic exchange capacity (AEC), high aspect ratio and good crystallinity. These artificial layered materials are prepared by hydrothermal method. The diameter of the LiAl LDH crystal in powder sample was determined by scanning electron microscopy (SEM). The morphology of epoxy/LiAl LDH nanocomposites were investigated by transmission electron microscopy (TEM) and powder X-ray diffraction techniques. TEM shows that pure LiAl LDH was dispersed in epoxy matrix to form sea type intercalated morphology whereas modified LiAl LDH forms both exfoliated and intercalated epoxy/LiAl LDH nanocomposites. The thermal characterizations were carried out by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The properties of epoxy/LDH nanocomposites exhibit better thermal properties as compared to pure epoxy polymer. [Copyright &y& Elsevier]

Abstract: A new type of zirconium phosphate/phosphonate derivative (Zr-P), with the functional group ∼Cen prepared and characterized by X-ray diffraction (XRD), solid state NMR, IR, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). This Zr-P is hybridized with an epoxy polymer to synthesize epoxy/zirconium phosphate (Zr-P) nanocomposite. XRD shows that the layered materials are well dispersed into the polymer matrix. TGA and DSC indicate the thermal properties of the nanocomposites. The morphology of nanocomposite was confirmed using transmission electron microscopy (TEM). The gas barrier property was measured by GPA, the combustion behavior was evaluated using the limiting oxygen index (LOI) test, and the transparency was measured by a UV–visible spectrophotometer. The material has a reasonably good optical property even with 10wt% loading of layered material to the epoxy polymer matrix. [Copyright &y& Elsevier]

Abstract: This paper describes the preparation and characterization of polymer-dispersed liquid crystal (PDLC)/layered double hydroxides (LDHs) nanocomposites. In this study, Mg–Al LDH was applied as two-dimensional host material, with the unique properties of higher anionic exchange capacity (AEC) and higher aspect ratio. Preparation of nanomaterials with a uniform, higher crystalline and surface charge density could be performed by a hydrothermal method. SEM and particle diameter analysis measurement, successfully obtained affords smaller crystallites with a higher aspect ratio, having a very narrow distribution of crystallite size. The structure formula were carried out by ICP-AES, EA and TGA. The major applications of LDHs based on the intercalation or exchange of specific guests as absorbents have been reported. However, it is seldom discussed to apply as optical materials. In this work, we have studied the Mg–Al LDH mixed with nematic liquid crystal and photo-polymer matrix. Photo-polymerization was induced by argon ion laser irradiation on the filled cells, which contain photo-initiator, monomers, liquid crystals and Mg–Al LDHs. Diffraction efficiency makes apparently increasing from 1.4 to 5.6%. When the sample was added 1phr of Mg–Al LDH, the diffraction efficiency rise to 5.6 from 1.4%, compared with original PDLCs. Polymerization induced the phase separation of polymer and liquid crystal in the PDLC film. Higher diffraction efficiency was observed when PDLC hybridized with inorganic LDH, which will change the polymerization rate of PDLC, and help the formation of the grating effect; therefore, the diffraction efficiency of the whole system was improved. The noteworthy factor of improving diffraction efficiency will be discussed in this paper. [Copyright &y& Elsevier]

Abstract: Vertically aligned carbon nanotubes (CNTs) were synthesized on a lithographically patterned silicon/silica substrate coated with an ultra thin iron film. The process was performed using different thickness of iron700–900 °C using a rapid heating and cooling system (RHCS) in a thermal chemical vapor deposition (CVD) chamber. The substrate was placed on the heater, which can be heated from room temperature to 900 °C within 20 s, and cooled from 900 °C to 250 °C within 25 s. Acetylene was used as the carbon precursor and the mixture of hydrogen and argon was adopted as carrier gas. An ultra high growth rate up to 50 μm/min was detected and a vertically aligned thick CNT array near 500 μm was attained under a low reaction pressure of 10 Torr. The control of CNT layer thickness on the silicon and the silica-patterned substrates was studied. Furthermore, the effects of iron layer thickness on the growth rate and the diameter of the vertically aligned CNTs were also investigated. [Copyright &y& Elsevier]

A C60-PEI-rGO hybrid was prepared by incorporating the fullerene (C60) on the surface of PEI-modified reduced graphene oxide (rGO) and then used to modify the epoxy (EP) resin. Subsequently, the structure of GO and C60-PEI-rGO hybrid were well characterized, showing that the C60 was homogenously anchored on the surface of PEI-rGO. The flame retardancy, mechanical properties, and thermal stability of as-prepared C60-PEI-rGO/EP nanocomposites were systematically investigated. Results show that the C60-PEI-rGO hybrid exhibits high flame retarding efficiency for EP. Specifically, the time to ignition of epoxy increases from 68 to 89 s with the addition of 1.0 wt% C60-PEI-rGO, which are unusual in polymer nanocomposites. In the meantime, the peaks of the heat release rate and total heat release of the modified epoxy reduce by 40.0% and 15.6%, respectively. The synergistic flame retardant mechanism of C60-PEI-rGO to EP is attributed to its unique structure combining both the high efficiency in capturing free radicals by C60, the barrier effect of layered of rGO and increase of crosslinking density of epoxy. It is shown that the thermal stability and mechanical properties of epoxy are simultaneously improved with the addition of C60-PEI-rGO. This work may pioneer a new and efficient method to fabricate fire retardant thermosetting resins with simultaneously other improved properties. [ABSTRACT FROM AUTHOR]

For high-security Internet-of-Everything (IoE) devices, a true random number (TRN)-based pseudohysteresis controller (PHC) is proposed to avoid both power side-channel attack (PSCA) and power injection attack (PIA) and reduce electromagnetic interference (EMI) without degrading performance of transient response and regulation. In addition, the TRN-based PHC uses an enhanced security randomizer to correctly generate a random number (RN) independent of the input power at the PSCA and PIA and converts the RN into a hysteresis window that constitutes the true random modulation switching frequency. Therefore, the TRN-based PHC ensures proper spread spectrum and low EMI. In addition, fast transient response is maintained due to inherent hysteresis control. Experimental results show that peak EMI noise is reduced from 89.72 to 54.32 dBμV and meets the specification of EN 55032 Class B even under the PIA interference up to 1 V. Furthermore, in case of 0.2 A-to-0.8 A load step, the method achieves a recovery time of 7.3 μs and an output voltage drop of 53 mV at a switching frequency of approximately 1 MHz, and the peak efficiency is 92.4%. [ABSTRACT FROM AUTHOR]

Abstract: The interaction of ultra-nanocrystalline diamond (UNCD) with neural stem cells (NSCs) has been studied in order to evaluate its potential as a biomaterial. Hydrogen-terminated UNCD (H-UNCD) films were compared with standard grade polystyrene in terms of their impact on the differentiation of NSCs. When NSCs were cultured on these substrates in medium supplemented with low concentration of serum and without any differentiating factors, H-UNCD films spontaneously induced neuronal differentiation on NSCs. By direct suppression of mitogen-activated protein kinase/extracellular signaling-regulated kinase1/2 (MAPK/Erk1/2) signaling pathway in NSCs using U0126, known to inhibit the activation of Erk1/2, we demonstrated that the enhancement of Erk1/2 pathway is one of the effects of H-UNCD-induced NSCs differentiation. Moreover, functional-blocking antibody directed against integrin β1 subunit inhibited neuronal differentiation on H-UNCD films. This result demonstrated the involvement of integrin β1 in H-UNCD-mediated neuronal differentiation. Mechanistic studies revealed the cell adhesion to H-UNCD films associated with focal adhesion kinase (Fak) and initiated MAPK/Erk1/2 signaling. Our study demonstrated that H-UNCD films-mediated NSCs differentiation involves fibronectin-integrin β1 and Fak–MAPK/Erk signaling pathways in the absence of differentiation factors. These observations raise the potential for the use of UNCD as a biomaterial for central nervous system transplantation and tissue engineering. [Copyright &y& Elsevier]

Abstract: This work studied the concentration of hydrolyzates obtained from dilute acid hydrolysis of rice straw using nanofiltration (NF). In order to minimize the Donnan exclusion effect of the membrane, the hydrolyzate solution was controlled at low pH value. Negative retentions of both furans and carboxylic acids were observed. The maximum separation factor of acetic acid over xylose was 49, while the maximum separation factor of acetic acid over arabinose was 52, when the system was operated at pH 2.9 and an applied pressure of 24.5–34.3bar. The separation factors of inhibitors over glucose became infinity due to the complete retention of glucose. The separation performance decreased when the operating temperature was increased from 25 to 40°C. The flux deterioration was recovered by flushing with 0.01N of NaOH and water. [Copyright &y& Elsevier]

This article proposes a dual voltage/current (V/C) inductance controller, which has good impedance tracking capability without any high-voltage stress problems. Besides, the proposed dual-mode phase-locked loop (D-PLL) technique can detect the phase difference between voltage and current of the antenna by fast tracking PLL and the accuracy-improved PLL for inductive and capacitive loads, thereby improving efficiency. Therefore, the 5G small base station on the receiver side (RX) can receive 27.8 W of power with 50% efficiency when the wall thickness to the transmitter side (TX) is 25.2 cm. In the case where the distance between TX and RX is close to zero, 50 W higher power with 90% efficiency can be achieved. Accordingly, the efficiency of resistive and inductive loads can be increased by 13% and 41%, respectively. [ABSTRACT FROM AUTHOR]

Compared to Si FETs, when the main GaN FET is in full zero voltage switching condition, maximum switching loss reduction can be achieved. Therefore, in this article, an active clamp flyback converter with GaN devices that implements fast ZVS by using the proposed dynamic resonant period control (DRPC) technique can reduce large transformer leakage inductance energy loss on the active resonant circuit. As the loading changes, the DRPC technique can dynamically adjust the on-time in auxiliary switch to prevent large voltage stress on the components in the primary side. In full load condition, the leakage energy loss can be reduced, thereby transferring more energy to the secondary side with maximum efficiency up to 94%. [ABSTRACT FROM AUTHOR]

The proposed digital low-dropout regulator uses nonlinear switching control (NLSC) technique to suppress voltage ripple to less than 6 mV when the switching noise voltage of a switching regulator operating in a power-saving mode is greater than 50 mV. In addition, the NLSC technique improves the current efficiency by reducing the quiescent current to less than 10 μA and reduces the switching power loss through variable switching frequency control. With a load step of 1–20 mA, the transient response time is 1.3 μs and the peak current efficiency is 99.8% at heavy loads. [ABSTRACT FROM AUTHOR]

This paper presents a modified negator-based switched-capacitor (NSC) dc–dc converter to achieve fine-grained voltage conversion ratios. Based on a concept of reconfiguring several 2:1 switched-capacitor (SC) converters in series and parallel at the last stage, the proposed asymmetrical shunt SC (ASSC) converter provides more controllable variables of forward gain and feedback gain to decide different power path interconnections and increase the available conversion ratios, with a little sacrifice of its slow switching limit output impedance. The switching loss of the bottom-plate parasitic capacitance in the ASSC converter is less than the switching loss of the NSC topology because the two moderate voltages instead of the power rail are fed to the last stage 2:1 SC unit and reduce the voltage swing. The bottom-plate swapping prototype further reduces the parasitic loss at high conversion ratios. To handle a large number of conversion ratios in closed-loop regulation, the ASSC converter uses the fast optimum ratio searching (FORS) technique, which evaluates the transient voltage drop to quickly search for target ratios and reduce the transient recovery time. A three-stage ASSC converter achieving 187 conversion ratios is fully integrated in the test chip, which is fabricated in 0.25-μm CMOS process with an active area of 7.14 mm2. Furthermore, 2389 conversion ratios can be derived in theory for a four-stage ASSC converter. The proposed reconfigurable SC converter provides an output voltage range of 0.4 to 2.8 V under no load conditions, and greater than 80% power efficiency at an output voltage level of 0.9 to 1.5 V over a load range of 3 to 9.5 mA. Due to the FORS technique, the measured transient recovery time is reduced from 7 to 1.5 μs in case of load current step of 7 mA. [ABSTRACT FROM AUTHOR]

Stacked mosfet structures made of low-voltage devices suffer from degraded transient response or large footprint when a capacitorless or dominant-pole compensated low-dropout (LDO) regulator biases the driver. Due to the self-stabilizing nature, the proposed stacked mosfet driver (SMD) technology effectively drives the power stage and greatly reduces the noise at the switching nodes for low cross regulation (CR) in a single-inductor dual-output (SIDO) converter. In addition, two inherent LDO regulators in SMD technology fully regulate the dual outputs with the advantage of low quiescent current at no-load conditions. The experimental results show that the test chip fabricated under the 0.25-μm process has low CR of 0.015 mV/mA and ultralow quiescent current of 5 μA under no-load conditions. [ABSTRACT FROM AUTHOR]

In this work, a series of porous epoxy composites containing microscale, hollow epoxy spheres were synthesized and characterized. First, microscale epoxy spheres were produced using amino-modified silica (AMS) particles with diameters of ∼1 μm through a base-catalyzed sol–gel route. The as-synthesized AMS particles were then characterized through Fourier-transform infrared, 13 C nuclear magnetic resonance (NMR), and 29 Si-NMR spectroscopy. The prepared core–shell particles were immersed into a 1 wt.% of HF solution for 24 h to remove the inner part of the silica core, leading to the formation of hollow spheres of epoxy with a wall thickness of ∼100 nm. These hollow epoxy spheres (HES) were characterized by scanning electron microscopy (SEM), Transmission electron microscopy, and thermogravimetric analysis (TGA). Finally, a series of hybrid materials was synthesized by performing thermal ring-opening polymerization reactions of epoxy resin in the presence of as-synthesized HES. Based on SEM observations on the morphology, the HES showed good dispersion capability in the polymer matrices, which led to a significantly reduced thermal conductivity and slightly decreased dielectric constant based on the transient plane source and LCR measurements, respectively. For example, the thermal conductivity and dielectric constant decreased by 49.3% and 12.6%, respectively, in the porous epoxy material synthesized with a final HES loading of about 10%. One possible reason was the large amount of air present in the material. Other physical characteristics such as the thermal and mechanical properties based on the results of TGA, differential scanning calorimetry, and dynamic mechanical analysis were investigated. [ABSTRACT FROM AUTHOR]

Abstract: Structural properties of GaN epilayers on wet-etched protruding and recess-patterned sapphire substrates (PSSs) have been investigated in detail using high-resolution double-crystal X-ray diffraction (DCXRD) and etch-pit density methods. The DCXRD results reveal various dislocation configurations on both types of PSSs. The etch pits of GaN on the recess PSS exhibit a regular distribution, i.e. less etch pits or threading dislocation density (TDD) onto the recess area than those onto the sapphire mesas. On the contrary, an irregular distribution is observed for the etch pits of GaN on the protruding PSS. A higher crystal quality of the GaN epilayer grown onto the recess PSS can be achieved as compared with that onto the protruding PSS. These data reflect that the GaN epilayer on the recess PSS could be a better template for the second epitaxial lateral overgrowth (ELOG) of GaN. As a result, the GaN epilayers after the ELOG process display the TDDs of around ∼106 cm−2. [Copyright &y& Elsevier]

Background: There are limited studies on the associations among parenting style, postpartum depression, and mother-infant bonding., Objective: The aims of this study are investigating how the parenting style of maternal grandparents predicted the mothers' bonding with their infants. The mediating roles of postpartum depression were also explored., Participants and Setting: A community sample of 227 postpartum women participated in this study. The participants primarily consisted of women who gave birth within six months (89.9%)., Methods: A cross-sectional and convenient sampling strategy was applied. Instruments were Parental Bonding Instrument, Edinburgh Postnatal Depression Scale, Postpartum Bonding Questionnaire, and Background Form., Results: In the young infant group (i.e. mothers with infants not older than three months), the results indicated that maternal protection could predict "impaired bonding" (β = 0.20, p < .05). This prediction was mediated by postpartum depression (β = 0.32, p < .001). In the older infant group, paternal and maternal care could directly predict "rejection and anger" (β = -0.20, -0.22 respectively, p < .05). Maternal protection could predict three bonding factors (β = 0.25-0.29, p < .05, 0.01). Postpartum depression acted as total mediator for "impaired bonding"(β = 0.45, p <. 001), and acted as partial mediators in "rejection and anger" and "anxiety about care" (β = 0.45, 0.28, ps < .001, .01)., Conclusions: Perceived parenting style (especially maternal protection) has impacts on adverse mother-infant bonding. Furthermore, the impact is more prominent on mothers of older infants. "Rejection and anger" could be the most vulnerable bonding factor affected by parenting style. Since postpartum depression mediates the predictions, interventions could concurrently address maternal parenting style and postpartum depression., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)