Synaptic organic electrochemical transistors with ionic liquids and ionic gels

Lee Donghyun Sungkyunkwan university 2021 국내석사

시냅스는 인간 감각기관에서부터 전달된 신경 신호 및 데이터를 전송하는 기관입니다. 시냅스에서는 시냅스 가소성을 통해 자극을 기억, 필터링 등의 기능을 하며 신호 처리의 효율성을 높입니다. 이를 모방한 시냅스 모방 소자들은 높은 효율성과 낮은 전력 소비의 이점을 가지고 많은 연구가 이루어 지고 있습니다. 폴리(3,4-에틸렌 디옥 시티 오펜) 폴리스티렌 설포네이트 (PEDOT:PSS)를 사용하는 유기전기 화학 트랜지스터(OECT)는 뛰어난 전기적 특성 및 장기 가소성, 단기 가소성등을 보여주어 새로운 시냅스 모방소자로 주목받고 있습니다. 이 연구에서, 우리는 이온 리퀴드와 자외선 경화 이온 젤과 PEDOT:PSS를 이용하여 전기적 특성 및 시냅스 가소성이 향상된 OECT를 보고합니다. 이온 리퀴드는 상온에서 액체상태로 존재하는 물질로써 양이온 및 음이온으로 가득 차있으며 높은 전도성 및 비휘발성 등의 장점으로 액체 전해질 대체 물질로 적합합니다. 이온 젤은 1-에틸-3-메틸리미다졸륨비스(트리플루오로메틸설포닐)이미드 ([EMIM] [TFSI]) / 폴리(에틸렌글리콜) 디아크릴레이트 (PEGDA) / 1-하이드록시실로헥실페닐 케톤 (광개시제) 를 첨가하여 제작하였다. 이온 리퀴드 및 기타 첨가 폴리머의 양 비율에 따라 진폭, 펄스 수 또는 펄스 지속 시간 등 게이트 바이어스 펄스에 따라 시냅스 가소성의 변화를 검증할 수 있었다. 이온 리퀴드 함량이 90% 인 이온젤의 경우엔 대체적으로 이온 리퀴드 및 리퀴드 함량이 더 적은 이온 젤 보다 높은 시냅스 가소성을 보여주었습니다. 이온 리퀴드의 경우 시냅스 모방 소자 뿐 아니라 가스 센서로도 많은 연구가 되고 있는 물질로써 위 연구에서도 이산화질소 가스를 이용하여 가스 센싱 테스트를 하였고, 이에 따라 소자의 전기적 특성 및 시냅스 가소성 변화를 확인하였습니다. In neuronal system, synapses are major components which can transmit and process data from human sensory neuron. Action potentials which are transferred from pre-synapse to post-synapse change according to stimulation strength, called synaptic plasticity, are the signal transmitted to brain. Through the changes of synaptic plasticity, synapses plays a role in memorizing the strength of stimuli. By mimicking synapse memory adaptation and filtering properties, a lot of synaptic devices are being studied and developed these days. Especially organic electrochemical transistors (OECTS) have been recently researched as synaptic devices. In particular, the OECTs with poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate)(PEDOT:PSS) have been studied with its outstanding neuromorphic functions like long-term plasticity and short-term plasticity. In this study, an OECT with ionic liquid and ultraviolet (UV)-cured ionic gel as an electrolyte and PEDOT:PSS as channel layer was investigated. Ionic liquid is a molten salt at room temperature and can be used as substitute of electrolyte with advantages of high conductivity, bifunctionality and non-volatility. UV-cured ionic gel was formed with ionic liquid / poly(ethylene glycol) diacrylate (PEGDA, crosslinker) / 1-hydroxycylohexyl phenyl ketone (photoinitiator). According to ratio of amount of ionic liquid and other additives, the synaptic plasticity changes at different gate bias pulsing like amplitude, number of pulses or duration time were verified. Many studies have already shown the Gas sensing property of ionic liquids. Due to IL's gas sensing property, we tested the detection of NO2 gas with our device. NO2 gas can absorb in EMIM TFSI IL by a reversible reaction. Specific ionic liquids show sensitivity and selectivity towards each different target gases. When target gas is applied, the gas reacts with the ions of IL, resulting in difference in ion proportion penetrating in the channel. As a result, the conductance of the channel is modulated. Here electrical properties of the device were measured by the flow of different concentration of NO2 gas.

Gas-phase oxidative purification of detonation nanodiamond in a fluidized bed reactor

Lee, Jaehoon Sungkyunkwan university 2016 국내석사

(A) study on attrition characteristics of iron ore by an air jet in Ggas-solid

Kang, Donghyun Sungkyunkwan university 2016 국내석사

Molecular dynamics insight into histidine tautomeric effect on the early stage of amyloid-beta peptide aggregation

Salimi, Abbas Sungkyunkwan university 2020 국내박사

In this dissertation, the main object is to elucidate the structural determinants of amyloid-beta (Aβ) aggregates under tautomeric effect of histidine residue at early stage of alzheimer's disease (AD) progression, using molecular dynamics simulation method. amyloid-beta (1-40) and (1-42) small oligomers are critical for AD formation. This research is the first to study the possible structural changes in amyloid-beta (1-40) and (1-42) homodimerization due to the tautomerism. So far the tautomric effect of three histidine residues in Aβ seqences during aggregation is largly unknown. There are two ε and δ tautomers for each histidine residue in equilibration. Due to experimental limitaions of tautomers charactrization, molecular dynamics (MD) simulation was performed to get detailed strucural infromation. In Aβ(1-40) homodimers the secondary sructure analysis showed higher propenisty to form β-sheet content for (δδδ) tautomer that could result in more toxicity compare with (εεε) as the most common form of Aβ. In addition, Aβ (1-42) (εεε) tautomer showed less β-sheet content comprae with (εδδ) that may indicate the importance of (εδδ) tautomer during aggregation as well. Also the importance of central hydrophobic core and C-terminals during aggregation is obvious through the obtained results such as contact map and avergae number of contacs between hydrophobic regions. This study is the first step to get better view of tautomerism effect on Aβ fragments aggregation at early stage thus the results could provide insight into the structural properties of Aβ aggregates, which may lead to find new ways and design novel inhibitors to cure AD. 이 논문의 주요 목적은 분자 역학 시뮬레이션 방법을 사용하여 알츠하이머병 (AD) 진행의 초기 단계에서 히스티딘 잔기의 호변 이성질체 효과 아래에서 아밀로이드-베타 (Aβ) 응집체의 구조적 결정 인자를 밝히는 것이다. 아밀로이드-베타 (1-40) 및 (1-42) 작은 올리고머는 AD 형성에 중요하다. 이 연구는 호변 이성질체로 인한 아밀로이드-베타 (1-40) 및 (1-42) 동종이량체 화의 가능한 구조적 변화를 연구한 첫 번째 연구이다. 지금까지 응집 하는 동안 Aβ 서열에서 3 개의 히스티딘 잔기의 타우톰 효과는 거의 알려지지 않았다. 각각의 히스티딘 잔기에 대해 2 개의 ε 및 δ 호변 이성질체가 평형화되어있다. 호변 이성질체 특성화의 실험적 제한으로 인해, 분자 구조학 (MD) 시뮬레이션을 수행하여 상세한 구조적 정보를 얻었다. Aβ (1-40) 동종이량체에서, 2 차 조사 분석은 (δδδ) 호변 이성질체에 대한 β- 시트 함량을 형성하도록 더 높은 예언을 나타내었고, 이는 가장 일반적인 형태의 Aβ로서 (εεε) 와 비교하여 더 많은 독성을 초래할 수 있다. 또한, Aβ (1-42) (εεε) 호변 이성질체는 응집 하는 동안 (εδδ) 호변 이성질체의 중요성을 나타낼 수 있는 (εδδ)와 비교하여 더 적은 β-시트 함량을 나타냈다. 또한 응집 하는 동안 중앙 소수성 코어 및 C- 말단의 중요성은 소수성 영역 사이의 접촉 맵 및 애버게이트 수와 같은 획득 된 결과를 통해 명백하다. 이 연구는 초기 단계에서 Aβ 단편 응집에 대한 호 변이 성질 효과를 더 잘 볼 수 있는 첫 번째 단계이므로 결과는 Aβ 응집체의 구조적 특성에 대한 통찰력을 제공 할 수 있으며, 이로 인해 새로운 방법을 찾고 AD 를 치료하는 새로운 억제제를 설계 할 수 있습니다.

Mixing and segregation characteristics in gas-solid bubbling fluidized beds with binary and ternary particles

Hong, Taekwoon Sungkyunkwan university 2018 국내석사

To develop the titanium process using ilmenite ore, the study on mixing and layer separation characteristics of multicomponent mixed particles in cylindrical fluidized bed and three-sectional tapered fluidized beds has been carried out. In cylindrical fluidized bed, a basic study was conducted to derive the appropriate operating condition by grasping the mixed bed separation characteristics according to the particle size distribution using ilmenite-coke binary mixed particles and ceramic beads-plastic media binary mixed particles used in the actual titanium process. To investigate the effect of particle size distribution on the mixing characteristics, two other binary solid mixtures were used, which have similar mean particle size and particle density, but their particle size distribution was different to each other. Column dimension is ID=0.14 m and H=2.14 m. Bed aspect ratio(L/D) was 3.0. Bed materials were two sets: one of bed materials was the mixture of ilmenite and coke, which has wide size distribution. The other bed materials were the mixture of ceramic beads and plastic media, which has narrow size distribution. Bed composition of ilmenite-coke mixture was determined to 0.7:0.3 by mass ratio. And, bed composition of ceramic beads-plastic media was 0.75:0.25 by mass ratio. Axial bed pressure drop was measured according to gas velocity. Bed composition was measured according to axial bed height by sampling. Bed pressure drop of ilmenite-coke mixture was maximized above U0=0.15 m/s, and fully fluidization was occurred. However, criterion of mixing to segregation was not found in the axial bed composition according to gas velocity. In the case of ceramic beads-plastic media mixture, bed pressure drop was maximized at U0=0.05 m/s, and the criterion of mixing to segregation was found at the same gas velocity. In three-sectional tapered fluidized bed, the objective of this study was to determine the effect of initial mixing ratio of glass beads and superficial gas velocity on mixing and segregation in a ternary system. The bed material was a ternary solid mixture consisting of three particles ilmenite (dp = 153 μm, ρs = 3,860 kg/m3), coke (dp = 582 μm, ρs = 1,762 kg/m3), and glass beads (dp=150 μm, ρs=2,500 kg/m3) with different particle sizes and densities. This ternary solid mixture at five different initial mass fractions of glass beads (15, 35, 55, 75, and 90%) with mass ratio of ilmenite to coke of 0.7:0.3 was tested. For the three-sectional tapered fluidized bed used in this study, it had the following three sections: a cylindrical type reaction zone (ID=0.14 m, H=0.28 m) at the top of the distributor, a tapered zone (cone angle=25 °, H=0.17 m) at the top of the reaction zone, and a cylindrical type expanded zone (ID=0.30 m, H=1.55 m) at the top of the tapered zone. Bed composition was determined after taking a sample in the axial from the sampling port on the side of the bed. Vertical segregation occurred at a given gas velocity based on results of axial bed composition analysis. When the bed was compared with the bottom reaction zone and the top expanded zone, segregation occurred with a difference of 25 wt% at maximum. The separation efficiency of glass beads was increased with increasing initial mass fraction of glass beads.

Hydrodynamic characteristics in a pressurized bubble column

Kim, Bongjun Sungkyunkwan university 2018 국내석사

To determine the hydrodynamic characteristics at the maximum system pressure of 3.5 MPa, the pressure drops with the liquid and gas properties were measured on a cylindrical stainless-steel column with an inner diameter of 0.097 m and a height of 1.8 m and the phase holdup was calculated with the superficial gas velocity. Gas used is air, tap water, aqueous ethanol and glycerol solution of various concentrations and kerosene were used. Gas density was controlled with system pressure and increased to a maximum of 42 kg/m3. Tap water, aqueous ethanol solution, aqueous glycerol solution and kerosene were used to measure the gas holdup as a function of the liquid properties and superficial gas velocity. The gas holdup tended to increase as the concentration of aqueous ethanol solution increased at all system pressures, and the gas holdup tended to decrease as the concentration of aqueous glycerol solution increased. Empirical correlation to predict gas holdup based on 708 data including gas holdup data and previous gas holdup data measured in this study was proposed. The predicted value of the gas holdup obtained in this study and the preceding literature was predicted well with an absolute average deviation of 8.5 %. 1C type optical probe was used to measure bubble size and bubble size distribution (BSD). The bubble size was measured in kerosene media as a function of system pressure and superficial gas velocity. Bubble size decreased with increasing system pressure and superficial gas velocity. Dynamic gas disengagement (DGD) technique was used to determine the size bubble fraction in the kerosene media. It was confirmed that the small bubble size fraction tended to increase with increasing the superficial gas velocity and system pressure.

Analysis of hydrodynamic characteristics in gas-solid fluidized beds using CPFD simulation

Lim, Jonghun Sungkyunkwan university 2016 국내박사

Bed structure characteristics of carbon nanotube agglomerates in fluidized beds

Hur, Seungjun Sungkyunkwan University 2024 국내석사

In this study, bed structure according to flow regime of fine particles in a gas–solid fluidized bed was investigated by measuring pressure drop and heat transfer coefficient. Two types of carbon nanotube (CNT) agglomerates with behavior similar to Geldart A and Geldart B group and two types of glass bead (GB) particles corresponding to Geldart A and Geldart B classification were used. CNTs fluidized in the form of agglomerates, and in some CNT agglomerates, a homogeneous expansion regime with suppressed generation of bubbles was observed. In the homogeneous expansion regime of CNT agglomerates, small-diameter channels coexisted, and due to unstable fluidization at low superficial gas velocity, intermittent bed collapses occurred. At low superficial gas velocities, the heat transfer coefficient of GB particles was maintained at a low value. As the superficial gas velocity increased and bubbles were generated, the heat transfer coefficient of GB particles was increased. In the homogeneous expansion regime of GB particles, heat transfer coefficient remained constant. As the superficial velocity increased, the heat transfer coefficient of the CNT agglomerates continuously increased, regardless of the flow regime transition. In the homogeneous expansion regime of CNT agglomerates, unlike Geldart A particles, agglomerates were confirmed to show movement within the bed as well as to possess dynamic bed structures in which the movement increased according to the increase of superficial gas velocity. 본 연구에서는 기체-고체 유동층에서 미분입자들의 흐름영역에 따른 bed structure를 압력강하 측정과 층 내에 수평 열전달 probe를 주입하여 열전달계수를 측정함으로써 확인하였다. 미분입자는 Geldart A와 B의 거동과 유사한 거동을 보이는 CNT 응집체 2종을 사용하였으며, 비교를 위해 Geldart A와 B 분류에 해당하는 glass bead 입자 2종을 사용하였다. CNT 응집체들은 응집체의 형태로 유동하였으며 일부 CNT 응집체에서는 공탑기체속도에 따라 기포의 발생이 억제된 상태로 유동하는 homogeneous expansion regime이 관찰되었다. CNT 응집체의 homogeneous expansion regime에서는 작은 직경의 채널이 공존하였고, 낮은 공탑기체속도에서는 유동이 불안정하여 간헐적인 층붕괴가 발생하였다. GB입자들의 열전달계수는 낮은 공탑기체속도에서 낮은 값을 유지하였으며, 공탑기체속도가 증가하여 기포가 발생함에 따라 증가하였다. GB입자들의 homogeneous expansion regime에서 열전달계수는 일정하게 유지되었다. 반면 CNT 응집체들의 열전달계수는 공탑기체속도가 증가함에 따라 flow regime 변화에 관계없이 지속적으로 증가하였다. CNT의 응집체의 homogeneous expansion regime에서는 Geldart A 입자와 달리 bed내에 입자들이 movement를 가지며 공탑기체속도가 증가함에 따라 movement가 증가하는 dynamic 한 bed structure를 가짐을 확인하였다.

Hydrodynamic characteristics and heat transfer at layer inversion point in three-phase fluidized beds with binary solids

Kim, Junyoung Sungkyunkwan university 2016 국내석사

Biochemical characterization of the TLR4-TIR domain complex

송동현 KAIST 2013 국내박사