The purpose of this study is to characterize the swirling secondary flow in the downstream of a pipe bend using a numerical simulation of the flow. The CFD (Computational Fluid Dynamics) software OpenFOAM is used to simulate the turbulent flow in pipes with elbow. Various turbulence models are benchmarked with the existing experimental data and a comparative study is performed to select an appropriate turbulence model for the analysis. Predictions made by the selected turbulence model are compared with the LDA (Laser Doppler anemometer) measurements from the experiments currently conducted to find the dependency of the flows on the Reynolds number. It is found that the swirl intensity of the secondary flow is a strong function of the radius of curvature of the bend and a weak function of the Reynolds number. Additionally, it is found that the dissipation of the swirl intensity is exponential in nature.

This paper presents the fabrication and characterization of the cross-point structure 20 × 20 μm 2 RRAM with TiO x /TiO y bi-layer insulator for synaptic application in neuromorphic systems. The measured oxygen concentration of the TiO x /TiO y switching layers of the fabricated devices using X-ray photoelectron spectroscopy analysis showed that the oxygen concentration ratio between TiO x and TiO y is ~ 1.5. After electroforming at ~ 5.62 V, the on/off ratio was ~ 76 at 0.2 V with the DC sweep voltage scheme. Synaptic behaviors including long-term potentiation (LTP) and long-term depression (LTD) were performed with 50 identical pulses for the implementation of RRAM into neuromorphic systems based on convolutional neural networks. Also, linearly increased (or decreased) 25 pulses were applied to the device so that the conductance changes linearly. The resulting linear LTP and LTD characteristics were mirror-symmetric, which could maximize the accuracy. For Hebbian learning, the device also mimicked the spike-timing-dependent plasticity properties with a conductance change from − 77.79% to 96.07% using a time-division multiplexing approach.

In this study, we have investigated the resistive switching behavior of multi-stacked PVA/ GO+PVA composite/PVA insulating layer-based RRAM (resistive random-access memory) as the annealing temperature of the insulating layer was varied between 100 °C, 150 °C, and 200 °C. The fabricated RRAM device with a multi-stacked insulating layer annealed at 200 °C showed relatively good switching properties with a high on/off ratio (∼10 4 ) and low V SET (3.5±0.29 V) and V RESET (−1.81±0.10 V), which were uniformly distributed over 100 DC sweep cycles. In terms of reliability, multi-stacked insulating layer-based RRAM devices exhibited good retention (>2×10 3 s) and DC sweep endurance (>80) due to the enhanced stability of the insulating layer by good dispersion and the thermal treatment. The conduction mechanisms of the device at low resistance state (LRS) and high resistance state (HRS) were analyzed through Ohmic conduction LRS and Poole-Frenkel emission of HRS, respectively. In addition, we demonstrated the filamentary switching mechanism of resistive switching in our proposed devices.

Korea Atomic Energy Research Institute (KAERI) established a multi-dimensional hydrogen analysis system to evaluate hydrogen release, distribution, and combustion in the containment of a Nuclear Power Plant (NPP), using MAAP, GASFLOW, and COM3D. In particular, KAERI developed an analysis methodology for a hydrogen flame acceleration, on the basis of the COM3D validation results against measured data of the hydrogen combustion tests in the ENACCEF and THAI facilities. The proposed analysis methodology accurately predicted the peak overpressure with an error range of approximately ±10%, using the Kawanabe model used for a turbulent flame speed in the COM3D. KAERI performed a hydrogen flame acceleration analysis using the multi-dimensional hydrogen analysis system for a severe accident initiated by a station blackout (SBO), under the assumption of 100% metal–water reaction in the Reactor Pressure Vessel (RPV), to evaluate an overpressure buildup in the containment of the Advanced Power Reactor 1400 MWe (APR1400). The magnitude of the overpressure buildup in the APR1400 containment might be used as a criterion to judge whether the containment integrity is maintained or not, when the hydrogen combustion occurs during a severe accident. The COM3D calculation results using the established analysis methodology showed that the calculated peak pressure in the containment was lower than the fracture pressure of the APR1400 containment. This calculation result might have resulted from a large air volume of the containment, a reduced hydrogen concentration owing to passive auto-catalytic recombiners installed in the containment during the hydrogen release from the RPV, and a lot of stem presence during the hydrogen combustion period in the containment. Therefore, we found that the current design of the APR1400 containment maintained its integrity when the flame acceleration occurred during the severe accident initiated by the SBO accident.

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