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Subacute oral toxicity of Dendropanax morbiferus H.Lév leaf extracts in Sprague-Dawley rats
Jiyong Park(Jiyong Park),Chang-Soo Cho(Chang-Soo Cho),Jun-Ho Song(Jun-Ho Song),Kwang Il Park(Kwang Il Park),Yeung Bae Jin(Yeung Bae Jin),Woo Hyun Kim(Woo Hyun Kim),Suk Kim(Suk Kim),Hu-Jang Lee(Hu-Jang 한국예방수의학회 2023 예방수의학회지 Vol.47 No.1
This study examined the subacute oral toxicity of Dendropanax morbiferus H.Lév leaves hot-water extracts (DMWE) using male and female Spargue-Dawley rats. Rats were orally administered the DMWE at dose levels of 0, 250, 500, 1,000, and 2,000 mg/kg body weight (BW) for four weeks. For experimental period, clinical signs and the number of deaths were examined, and feed intake and BW of all experimental animals were measured once a week for four weeks. At the end of the experiment, blood samples were collected from all rats, and all animals were euthanized and autopsies were performed to collect major organs. No dead animals were found during the experimental period. In addition, no differences were found between control and DMWE-treated groups in feed intakes, BW changes, organ weights, clinical signs, hematological parameters, and serum biochemical parameters. The results of this study provided evidence that oral administration of DMWE at the dose of 2,000 mg/kg BW is safe in rats and may not exert severe toxic effects.
Jiyong Woo,Daeseok Lee,Euijun Cha,Sangheon Lee,Sangsu Park,Hyunsang Hwang IEEE 2013 IEEE electron device letters Vol.34 No.12
<P>In this letter, we discuss our technique for fabricating a vertically stacked ReRAM device composed of one selector and one resistor (1S-1R). We demonstrate that the nanoscale via-hole structure and 1-kb array architecture of selector device exhibit higher current density ( ~ 10<SUP>7</SUP> A/cm<SUP>2</SUP>) and reliability, and we introduce bipolar resistive switching element-a conductive-bridge RAM that can be stacked on top of the selector device. The resulting integrated 1S-1R device performs robust bipolar switching operations and significantly reduces the leakage current in cross-point applications.</P>
Woo, Jiyong,Moon, Kibong,Song, Jeonghwan,Kwak, Myounghoon,Park, Jaesung,Hwang, Hyunsang Institute of Electrical and Electronics Engineers 2016 IEEE transactions on electron devices Vol. No.
<P>In this brief, we demonstrate the multilevel cell (MLC) characteristics of an HfO2-based resistive memory (RRAM) array as a synaptic element for neuromorphic systems. We utilize various programming schemes to linearly change the resistance state with either set voltage/pulse ramping or gate voltage ramping. Our results reveal that the MLC relates to the size of the conductive filament involved in the movement of oxygen vacancies with respect to applying pulses. Thus, by optimizing the pulse for a set condition, such as an identical pulse, we achieve linearly increased MLC behavior, thereby enabling a high accuracy for pattern recognition in neuromorphic systems.</P>
Woo, Jiyong,Moon, Kibong,Song, Jeonghwan,Lee, Sangheon,Kwak, Myounghun,Park, Jaesung,Hwang, Hyunsang IEEE 2016 IEEE electron device letters Vol.37 No.8
<P>We analyze the response of identical pulses on a filamentary resistive memory (RRAM) to implement the synapse function in neuromorphic systems. Our findings show that the multilevel states of conductance are achieved by varying the measurement conditions related to the formation and rupture of a conductive filament. Furthermore, abrupt set switching behavior in the RRAM leads to an unchanged conductance state, leading to degradation in the accuracy of pattern recognition. Thus, we demonstrate a linear potentiation (or depression) behavior of conductance under identical pulses using the effect of barrier layer on the switching, which was realized by fabricating an RRAM on top of an Al electrode. As a result, when the range of the conductance is symmetrically controlled at both polarities, a significantly improved accuracy is achieved for pattern recognition using a neural network with a multilayer perceptron.</P>
Jiyong Woo,Padovani, Andrea,Kibong Moon,Myounghun Kwak,Larcher, Luca,Hyunsang Hwang IEEE 2017 IEEE electron device letters Vol.38 No.9
<P>We perform a comparative study of HfO2 and Ta2O5 resistive switching memory (RRAM) devices for their possible application as electronic synapses. By means of electrical characterization and simulations, we link their electrical behavior (digital or analog switching) to the properties and evolution of the conductive filament (CF). More specifically, we identify that bias-polarity-dependent digital switching in HfO2 RRAM is primarily related to the creation and rupture of an oxide barrier. Conversely, the modulation of the CF size in Ta2O5 RRAM allows bias-polarity-independent analog switching with multiple states. Therefore, when the Ta2O5 RRAM is used to implement a synapse in multilayer perceptron neural networks operated by back-propagation algorithms, patterns in handwritten digits can be recognized with high accuracy. Index</P>
Jiyong Woo,Belmonte, Attilio,Redolfi, Augusto,Hyunsang Hwang,Jurczak, Malgorzata,Goux, Ludovic IEEE 2016 IEEE electron device letters Vol.37 No.2
<P>In this letter, we experimentally investigate data retention in a copper (Cu)-based conductive bridge random-access memory device at a low current regime (10 mu A) in which retention is governed by factors other than just the conductive filament. Our findings show that the retention characteristics are determined by the local chemical potential of Cu between the conductive filament and its surrounding medium. Furthermore, the retention tendencies are described by the electrochemical reaction in accordance with the potential difference of Cu ions. Therefore, an appropriate quantity of Cu ions around the filament is important for achieving thermally reliable high and low resistance states over time.</P>
Woo, Jiyong,Hwang, Hyunsang The Electrochemical Society 2016 ECS journal of solid state science and technology Vol.5 No.3
<P>We show that the motion of Ag atoms in an Ag2S-based conductive bridge RAM system can be utilized for threshold-type selector applications. We found that the instability of an Ag filament could be increased in low current operation, where only few limited Ag ions are allowed to form a filament, and this resulting small filament enables the transition of a non-volatile memory system to a volatile mode. Furthermore, the enhanced activity of Ag atoms at elevated temperatures promotes the self-dissolution process when the bias is removed. As a result, threshold switching behavior with suppressed hysteresis can be achieved. (c) 2016 The Electrochemical Society. All rights reserved.</P>
Won Woo Yoon,Weon Shik Han,Jeonghwan Hwang,Jung-Woo Kim,Jiyong Lee 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2
The effect of various physicochemical processes, such as seawater intrusion, on the performance of the engineered barrier should be closely analyzed to precisely assess the safety of high-level radioactive waste repository. In order to evaluate the impact of such processes on the performance of the engineered barrier, a thermal-hydrological-chemical model was developed by using COMSOL Multiphysics and PHREEQC. The coupling of two software was achieved through the application of a sequential non-iterative approach. Model verification was executed through a comparative analysis between the outcomes derived from the developed model and those obtained in prior investigations. Two data were in a good agreement, demonstrating the model is capable of simulating aqueous speciation, adsorption, precipitation, and dissolution. Using the developed model, the geochemical evolution of bentonite buffer under a general condition was simulated as a base case. The model domain consists of 0.5 m of bentonite and 49.5 m of granite. The uraninite (UO2) was assigned at the canister-bentonite interface as the potential source of uranium. Assuming the lifetime of canister as 1,000 years, the porewater mixing without uranium leakage was simulated for 1,000 years. After then, the uranium leakage through the dissolution of uraninite was initiated and simulated for additional 1,000 years. In the base case model, where the porewater mixing between the bentonite and granite was the only considered process, the gypsum tended to dissolve throughout the bentonite, while it precipitated in the vicinity of bentonite-granite boundary. However, the precipitation and dissolution of gypsum only showed a limited effect on the performance of the bentonite. Due to the low solubility of uraninite in the reduced environment, only infinitesimal amounts of uranium dissolved and transported through the bentonite. Additional cases considering various environmental processes, such as seawater or cement porewater intrusion, will be further investigated.