The learning and inference efficiencies of an artificial neural network represented by a cross‐point synaptic memristor array can be achieved using a selector, with high selectivity (Ion/Ioff) and ...sufficient death region, stacked vertically on a synaptic memristor. This can prevent a sneak current in the memristor array. A selector with multiple jar‐shaped conductive Cu filaments in the resistive switching layer is precisely fabricated by designing the Cu ion concentration depth profile of the CuGeSe layer as a filament source, TiN diffusion barrier layer, and Ge3Se7 switching layer. The selector performs super‐linear‐threshold‐switching with a selectivity of > 107, death region of −0.70–0.65 V, holding time of 300 ns, switching speed of 25 ns, and endurance cycle of > 106. In addition, the mechanism of switching is proven by the formation of conductive Cu filaments between the CuGeSe and Ge3Se7 layers under a positive bias on the top Pt electrode and an automatic rupture of the filaments after the holding time. Particularly, a spiking deep neural network using the designed one‐selector‐one‐memory cross‐point array improves the Modified National Institute of Standards and Technology classification accuracy by ≈3.8% by eliminating the sneak current in the cross‐point array during the inference process.
An artificial neural network consisting of a hardware‐based cross‐point synaptic memristor array should employ selectors with two‐terminal electrodes to prevent an undesired sneak current and to improve learning and inference efficiencies. Here, a highly reliable super‐linear‐threshold‐switching selector with multiple jar‐shaped Cu‐filaments in the amorphous Ge3Se7 resistive switching layer by controlling the Cu ion concentration depth profile is developed.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Although hexagonal boron nitride (h-BN) is a good candidate for gate-insulating materials by minimizing interaction from substrate, further applications to electronic devices with available ...two-dimensional semiconductors continue to be limited by flake size. While monolayer h-BN has been synthesized on Pt and Cu foil using chemical vapour deposition (CVD), multilayer h-BN is still absent. Here we use Fe foil and synthesize large-area multilayer h-BN film by CVD with a borazine precursor. These films reveal strong cathodoluminescence and high mechanical strength (Young's modulus: 1.16 ± 0.1 TPa), reminiscent of formation of high-quality h-BN. The CVD-grown graphene on multilayer h-BN film yields a high carrier mobility of ∼ 24,000 cm(2) V(-1) s(-1) at room temperature, higher than that (∼ 13,000 (2) V(-1) s(-1)) with exfoliated h-BN. By placing additional h-BN on a SiO2/Si substrate for a MoS2 (WSe2) field-effect transistor, the doping effect from gate oxide is minimized and furthermore the mobility is improved by four (150) times.
Step-skew is a common technique for eliminating the cogging torque of a target harmonic order in permanent magnet synchronous motors (PMSMs). However, when step-skew is applied to the rotor, the ...cogging torque of the target harmonic order is not completely eliminated due to 3-D leakage flux. Therefore, the 3-D leakage flux should be considered in designing a PMSM with step-skew for cogging torque reduction. The most accurate way to consider the 3-D leakage flux is to perform 3-D finite element analysis (FEA), but it has the disadvantage of high computation time. To resolve this challenge, this article proposes a design method that utilizes transfer learning to reduce the time for 3-D FEA while maintaining accuracy. Through the proposed method, a large amount of 2-D FEA-based data and a small amount of 3-D FEA-based data are used instead of a large amount of 3-D FEA-based data, with similar accuracy as using a large amount of 3-D FEA-based data, and the computational time is highly reduced. Finally, a prototype is fabricated and tested to verify the validity of the proposed design method for cogging torque reduction.
Preterm birth (PTB) refers to delivery before 37 weeks of gestation. Premature neonates exhibit higher neonatal morbidity and mortality rates than term neonates; therefore, predicting and preventing ...PTB are important. In this study, we investigated the potential of using short-chain fatty acid (SCFA) levels, specific vaginal microbiota-derived metabolites, as a biomarker in predicting PTB using gas chromatography/mass spectrometry. Cervicovaginal fluid (CVF) was collected from 89 pregnant women (29 cases of PTB vs. 60 controls) without evidence of other clinical infections, and SCFA levels were measured. Furthermore, the PTB group was divided into two subgroups based on birth timing after CVF sampling: delivery ≤ 2 days after sampling (
= 10) and ≥2 days after sampling (
= 19). The concentrations of propionic acid, isobutyric acid, butyric acid, valeric acid, hexanoic acid, and heptanoic acid were significantly higher in the PTB group than in the term birth (TB) group (
< 0.05). In particular, the concentrations of propionic acid, isobutyric acid, hexanoic acid, and heptanoic acid were continuously higher in the PTB group than in the TB group (
< 0.05). In the delivery ≤ 2 days after sampling group, the propionic acid, isobutyric acid, hexanoic acid, and heptanoic acid levels were significantly higher than those in the other groups (
< 0.05). This study demonstrated a significant association between specific SCFAs and PTB. We propose these SCFAs as potential biomarkers for the prediction of PTB.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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Sorafenib, a potent anticancer drug, has low absorption in the gastrointestinal tract due to its poor aqueous solubility. The main purpose of this investigation was to design ...sorafenib nanoparticle using a newly developed technique, nanoparticulation using fat and supercritical fluid (NUFS™) to improve the absorption of sorafenib. The quality by design (QbD) tool was adopted to define the optimal formulation variables: hydroxypropyl methyl cellulose (HPMC), polyvinyl pyrrolidone K30 (PVP), and poloxamer. The studied response variables were particle size of nanoparticle, dissolution (5, 60, and 180 min), drug concentration time profile of nanoparticle formulations, and maximum drug concentration. The result of particle size revealed that an increase in concentration of poloxamer and HPMC decreased the particle size of nanoparticles (p < 0.05). Likewise, the concentration of drug release at different time point (5, 60, and 180 min) showed HPMC and poloxamer had positive effects on drug dissolution while PVP had negative effects on it. The design space was built in accordance with the particle size of nanoparticle (target < 500 nm) and dissolution of sorafenib (target > 7 µm/mL), following failure probability analysis using Monte Carlo simulations. In vivo pharmacokinetics studies in beagle dogs demonstrated that optimized formulation of sorafenib (F3 and F4 tablets) exhibited higher blood drug profiles indicating better absorption compared to the reference tablet (Nexavar®). In conclusion, this study showed the importance of systematic formulation design for understanding the effect of formulation variables on the characteristics of nanoparticles of the poorly soluble drug.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Thermal management has been considered as one of the critical issues in proton exchange membrane fuel cell (PEMFC). Key roles of thermal management system are maintaining optimal operating ...temperature of PEMFC and diminishing temperature difference over a single fuel cell and stack. Severe temperature difference causes degradation of performance and deterioration of durability, so understanding temperature distribution inside a single fuel cell and stack is crucial. In this paper, two-phase HFE-7100 cooling method is suggested for PEMFC thermal management and investigated regarding temperature change inside a fuel cell. Also, the results are compared to single-phase water cooling method. Numerical study of temperature distribution inside a single PEMFC is conducted under various conditions for the two different cooling methods. Fuel cell model considering mass transfer, electrochemical reaction and heat transfer is developed.
The result indicates that two-phase HFE-7100 cooling method has an advantage in temperature maintenance and temperature uniformity than single-phase water cooling method, especially in high current density region. It is also revealed that the cell temperature is less dependent on system load change with two-phase cooling method. It indicates that the fuel cell system with two-phase cooling method has high thermal stability. In addition, the effect of coolant flow rate and coolant inlet pressure in two-phase HFE-7100 cooling method are discussed. As a result, two-phase cooling method showed reliable cooling performance even with low coolant flow rate and the system temperature increased as coolant pressure rose.
•Two-phase HFE-7100 cooling method is suggested for PEMFC thermal management.•Numerical study investigating temperature distribution inside PEMFC is conducted.•Single-phase water cooling and two-phase HFE-7100 cooling methods are compared.•Two-phase cooling shows better thermal performance than single-phase cooling.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The functional status of dynamic microglial cells plays an important role in maintaining homeostasis of microenvironment in CNS. In a previous study, we reported that microglia phenotype might be ...involved in stress vulnerability and depression recurrence. Here, we aimed to clarify a character of microglia exposed persistently to glucocorticoid (GC), which is representative a stress hormone, in primary cultured microglial cells. Five nanomolars of dexamethasone (DEX, GC agonist) for 72 h decreased CX3CR1 and CD200R expression and induced ramified form of microglial cells in similar morphology to in vivo resident microglia. However, the ramified form of microglia did not increase microglia signature genes such as P2RY12, OLFML3, TMEM119, and TGFBR1. In addition, DEX-treated microglia showed a reduction of phagocytosis function, pro-and anti-inflammatory cytokine production, and cell proliferation. DEX washout did not restore these changes. Based on transcriptomic analysis and functional characters of DEX-treated microglia, we performed senescence-associated beta-galactosidase (SA-β gal) assay in DEX-treated microglia and DEX-treated microglia showed more SA-β gal activity with alteration of cell cycle-related genes. Thus, our results suggest that DEX can induce a specific phenotype of microglia (like-senescence).
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Dye-adsorbing tungsten trioxide (WO3) powders were prepared by a simple wet chemical hydrothermal method at 120°C. In order to study the effect of specific surface area on the dye-adsorption ...properties, various morphologies of WO3 powders were synthesized using different concentrations of a structure-directing agent (citric acid). The morphology, structure, specific surface area, and adsorption characteristics of the synthesized WO3 powders were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller (BET) method, and UV–vis adsorption spectroscopy, respectively. The BET measurements showed different surface area values for the samples prepared at different concentrations of citric acid, and the adsorption capacity increased as the surface area increased. WO3 nanorods synthesized using 0.2mol of citric acid showed the largest surface area of 81.5m3/g and the highest adsorption capacity of 57.6mg/g at a pH of 7.0.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Two-phase cooling method is suggested for thermal management of PEMFC.•Boiling heat transfer coefficient of HFE-7100 in mini-channels is examined.•Wall temperature with two-phase cooling is ...presented under various conditions.•Coolant channel pressure determines operating temperature of PEMFC.•Two-phase cooling method is effective for temperature uniformity inside a stack.
The aim of this paper is to investigate two-phase heat transfer of HFE-7100 in mini-channels and its cooling performance in order to determine its effectiveness for a fuel cell application. Firstly, characteristics of two-phase boiling heat transfer of HFE-7100 is analyzed. It is demonstrated that two-phase boiling heat transfer coefficient of HFE-7100 in mini-channels is strongly dependent on heat flux and vapor quality but less sensitive to mass flux. Critical heat flux is observed when wall superheat is over 25 K and flow visualization method is used to examine a flow pattern change.
In the second part, cooling performance and wall temperature change is investigated. Under heat generation ranges from a fuel cell, wall temperature is maintained at desirable operating temperature of polymer electrolyte membrane fuel cell (60–80 °C) and temperature difference is lower than 0.5 °C. At critical heat flux condition, wall temperature rises to over 90 °C. Also, wall temperature increases from 63.5 °C to 71.6 °C when channel pressure rises from 1.0 bar to 1.5 bar. Lastly dynamic response in wall temperature with the coolant pump control is investigated. It is found that this control method is effective to maintain low temperature difference (less than 1.5 °C) and the intermittent pump operating mode can reduce pump energy consumption.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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