Daegu Gyeongbuk Institute of Science and Technology
DGIST Library Institutional RepositoryNot a member yet
12664 research outputs found
Sort by
다중 모드 위장관 내시 현미경 및 망막하 정밀 주입을 위한 인공지능 신호 처리를 사용한 지능형 진단 및 미세 로봇 수술 시스템
No full textMultimodal endo-microscopy;Handheld robotic microinjector;AI-assisted scanning pattern regulation control for imaging;AI-assisted adaptive controller for robotic hand tremor compensationⅠ. INTRODUCTION 1
1.1 Study Background 1
1.2 Optical Biopsy with Endomicroscopy 2
1.3 Robot-assisted Ophthalmic Microsurgery 4
1.4 Study Objectives and Scopes 6
II. WORKING PRINCIPLE 7
2.1 Intelligent Multimodal Endomicroscopy 7
2.1.1 Confocal Fluorescent Microscopy (CFM) 7
2.1.2 Optical Coherence Tomography (OCT) 11
2.1.3 Multimodal Imaging (CFM & OCT) 14
2.1.4 Resonant Fiber Scanner 15
2.1.5 Asymmetric Fiber Cantilever 18
2.1.6 Lissajous Scanning 22
2.2 Intelligent Handheld Robotic Microinjector 27
2.2.1 Common-path OCT (CP-OCT) 27
2.2.2 Fabry-Perot Interferometer (FPI) 30
2.2.3 Multimodal Force and Distance Measurements (FPI & CP-OCT) 34
2.2.4 Handheld Motion Compensation 37
III. SYSTEM DESIGN AND IMPLEMENTATION 40
3.1 Intelligent Multimodal Endomicroscopy 40
3.1.1 System Configuration 40
3.1.2 Compact Imaging Probe 44
3.1.3 Mathematical Modeling on Asymmetric Scanning Cantilever 48
3.1.4 Scanning Parameter Determination for Optimal Lissajous Pattern 65
3.1.5 Artificial Intelligence-based Scanning Pattern Regulation Controller 71
3.1.6 Compact Depth Scanner via Mechanical Amplifier 77
3.2 Intelligent Handheld Robotic Microinjector 82
3.2.1 System Configuration 82
3.2.2 Sensorized Needle 83
3.2.3 Artificial Intelligence-based Adaptive Motor Controller 86
IV. EXPERIMENTAL RESULTS 96
4.1 Intelligent Multimodal Endomicroscopy 96
4.1.1 Implemented System 96
4.1.2 Imaging Results on Test Specimens 99
4.1.3 Imaging Results on Biological Samples 103
4.2 Intelligent Handheld Robotic Microinjector 105
4.2.1 Performances of Distance and Force Measurements 105
4.2.2 Motorized Injection Performance on Eye Phantom 108
V. CONCLUSION AND FUTURE WORKS 112
5.1 Conclusion 112
5.2 Future Works 113
5.2.1. Multimodal Endomicroscopy with Force Measurement 113
5.2.2. Integrated Microinjection System with an Intraoperative OCT Imaging 115
REFERENCES 116
국문 요약문 127DoctordCollectio
계면 Dzylaoshinskii-Moriya 상호작용을 포함하는 키랄 대칭 파괴 시스템에서 스핀 궤도 토크에 의한 자화 동역학 연구
No full textSpin-Orbit torque;interfacial Dzyaloshinskii-Moriya interaction;Magnetization switching;Magnetic energy;ChiralitySpin-orbit torque (SOT) induced magnetization switching has potential in application on magnetic material based memory and logic devices because of its benefits of a fast writing speed and efficient power consumption. However, to achieve deterministic SOT induced magnetization switching in a perpendicular magnetic anisotropy (PMA) system, applying an additional external in- plane magnetic field is essential. Here, I focus on the chirality of a magnetic ordering system. It is because there are a few reports that achieve the field-free SOT induced magnetization switching when chirality is considered. However, previous researches are limited into phenomenological point of view only, therefore, systematic analysis of the effect of the chiral spin texture on deterministic magnetization switching is still scarce. Through this thesis, I propose that the possibility of field-free switching of magnetization by SOT when the chirality is introduced and prove its underlying mechanism. I observed the chirality- dependent SOT induced magnetization switching in various chiral symmetry broken system with structure of a heavy metal (HM) /ferromagnet (FM) bilayer. With micromagnetic simulations and experiments, I confirmed the role of the Néel-type chiral spin texture in terms of magnetization dynamics, magnetic energy, and torques. From the results, I conclude that deterministic field-free switching can be achieved when the DMI of the system corresponds with the chirality of spin texture and find major parameter is determined strongly from interfacial Dzyaloshinskii-Moriya interaction.| 반전 대칭 파괴된 스핀-궤도 결합 물질에서 나타나는 스핀 궤도 토크는 빠른 속도와 높은 에너지 효율면에 있어 초저전력/초고속 자성기반 차세대 메모리 혹은 논리 소자 개발에 사용될 수 있는 가능성으로부터 많은 각광을 받고 있다. 하지만 스핀 궤도 토크를 이용한 정보 입력 소자는 높은 집적률을 가지는 수직자기 이방성인 경우에 확정적인 정보 입력이 불가능하고 이는 하나의 문제로 떠오르고 있다.
본 연구는 계면 Dzyaloshinskii-Moriya 상호작용으로 알려져있는 비대칭 상호작용을 이용할 경우 시스템이 보유하고 있는 본질적 특성만을 가지고 수직자기 이방성 시스템에서 스핀 궤도 토크를 이용한 정보 입력을 위해 가장 주요하게 요구되는 무자기장 자화 스위칭이 가능함을 이론, 전산모사, 그리고 실험을 통해 밝힌다.
비대칭 상호작용을 이용해 스핀 궤도 토크 기반 무자기장 자화 반전을 달성하기 위해서는 공간상의 비공선형 스핀 배열의 형성이 필수적이며, 이 논문에서 제시된 다양한 이론, 전산모사 그리고 실험은 비공선형 스핀 배열이 비대칭 상호작용에 의해 확정적인 자화 반전을 가능하게 하는 면 수직 방향 토크를 기여한다는 것을 뒷받침한다. 다음과 같은 시스템 본질적인 특성만을 이용한 스핀 궤도 토크 자화 반전 연구는 더 우수한 효율성을 가지는 자성 기반 정보 소자 개발에 기여할 것이다.List of Contents
Abstract i
List of Contents ii
List of Figures · iv
I. INTRODUCTION 1
ⅠI. ROLE OF CHIRAL SPIN CONFIGURATION FOR FIELD-FREE SPIN-ORBIT
TORQUE INDUCED MAGNETIZATION SWITCHING
2.1 Overview 4
2.2 Sample fabrication 6
2.3 Spin-orbit torque induced magnetization switching measurement 8
2.4 Magnetization switching simulation by pure spin current injection 11
2.5 Conclusion 18
ⅠII. Z-DIRECTIONAL TORQUE COMPONENTS IN SPIN-ORBIT TORQUE BY
LATERAL SYMMETRY BROKEN NONCOLLINEAR SPIN TEXTURE
3.1 Overview · 18
3.2 Magnetization switching simulation with noncollinear spin texture 20
3.3 System energy and z directional torque components 24
3.4 Experimental observation of spin-orbit torque switching
3.4.1 Helium ion irradiation induced system modulation 33
3.4.2 Spin-orbit torque switching with noncollinear spin texture · 53
3.4 Conclusion 58
ⅠV. CHIRALITY-DEPENDENT ENERGY INDUCED BY SPIN-ORBIT TORQUE-DRIVEN
ARTIFICIAL SPIN TEXTURE
4.1 Overview · 59
4.2 Theoretical evaluation of system energy variation by artificial spin texture 62
4.3 Experimental observation of system energy variation
4.3.1 Sample fabrication 64
4.3.2 Azimuthal angle dependent system energy 72
4.3.3 Degree of anisotropy asymmetry dependent system energy 76
4.4 Micromagnetic Simulations · 81
4.5 Conclusion 84
V. SUMMARY OF THESIS · 84DoctordCollectio
SIMULTANEOUS PATTERNING OF A TRANSPARENT ELECTRODE AND A PHOTOTHERMAL LAYER, AND A TRANSPARENT ELECTRODE STRUCTURE MANUFACTURED THROUGH THE SAME
No full text본 발명은 투명 전극 및 광열층의 동시 패터닝 방법 및 이를 통하여 제조된 투명 전극 구조체를 개시한다. 본 발명은 기판을 세정하는 단계; 상기 세정된 기판 상에 고분자 전해질 잉크를 이용하여 고분자 전해질 패턴을 형성하는 단계; 및 상기 고분자 전해질 패턴이 형성된 기판 상에 금속 박막을 증착하여 투명 전극 및 광열층을 동시에 형성하는 단계;를 포함하고, 상기 투명 전극은 상기 기판 상에 적층된 상기 고분자 전해질 패턴 및 상기 금속 박막을 포함하며, 상기 광열층은 상기 기판 상에 형성된 상기 금속 박막을 포함하는 것을 특징으로 한다
Analytical Modeling and Implementation of an Imaging Cantilever with a Thermoplastic Stiffener
No full textPiezoelectric (PZT) tube actuators have been widely used in miniature resonant scanning systems due to their low operation voltage and high-frequency bandwidth. Although several designs of asymmetric stiffeners have been implemented to mitigate the inherent parasitic deflection of PZT actuators, to the best of the authors' knowledge, finite element analysis (FEA) has only been used to predict the harmonic response of asymmetric fiber cantilevers. This study presents the analytical modeling of an arbitrary-shaped resonant fiber cantilever based on Castigliano's and Rayleigh-Ritz's methods. The proposed model is designed to quickly identify and adjust the influential variables of asymmetric stiffeners, comparable to FEA in terms of its high prediction accuracy and fewer numerical computations. In addition, a thermoplastic polystyrene sheet was adopted to fabricate the asymmetric stiffener due to its sufficient stiffness, low cost, and high fabrication repeatability. The proposed model could accurately predict frequency separation at various fabrication tolerances, with the most significant errors from the experiments of 3.21%, comparable to FEA prediction results of 3.00%. Imaging results were acquired from an ex-vivo rat's stomach and small intestine using the implemented asymmetric fiber cantilever and compared with their histological images. © IEEE.FALSEsciescopu
Mapping the low tolerance factor Bi(Li1/3Zr2/3)O3 end member and MPB composition nexus in Bi1/2Na1/2TiO3-based ceramics
No full textThe structural stability of an end member Bi(Li1/3Zr2/3)O3 was calculated by a first principal method and lead-free perovskite piezoelectric system (1 − x)Bi1/2Na1/2TiO3-xBi(Li1/3Zr2/3)O3 (0 ≤ x ≤ 0.05 [(1 − x)BNT-xBLZ] was synthesized. Rietveld analysis of the XRD data shows the coexistence of rhombohedral (R3c) and tetragonal (P4bm) phases for the compositions (x = 0.01 and 0.02). A remarkable shift in the transition temperature (TF-R) below room temperature was observed with increasing BLZ content. In the vicinity of the coexistence between rhombohedral and tetragonal phases, the sample with x = 0.02 exhibits enhanced remnant polarization (Pr ∼ 34 µC/cm2) and an optimal direct piezoelectric coefficient (d33 ∼ 107 pC/N) attributed to the reduction of energy barriers for polarization switching. However, further addition of BLZ manifested a coexistence of nonergodic and ergodic relaxor phases at or near room temperature, particularly for the x = 0.03 composition, which exhibits a maximum electrostrain of 0.13 % with normalized strain (Smax/Emax = 173 pm/V). Furthermore, a relationship between the tolerance factor (t) of end members and the morphotropic phase boundary (MPB) compositions was explored, which provides valuable insight into the specific range of tolerance factors for MPB compositions. It was found that the t value associated with the formation of the MPB is confined to a relatively narrow range (t = 0.9750–0.9757) in (1 − x)BNT-xBi(M1M2)O3 systems featuring low tolerance factor end members. These findings offer a valuable reference point for swiftly identifying the approximate region where the MPB is likely to occur in newly designed solid solutions. © 2024FALSEsciescopu
Modulating Nanostructures with Polyvinylpyrrolidone: Design and Development of a Porous, Biocompatible, and pH-Stable Core-Shell Magnetic Microrobot for Demonstrating Drug Absorption from Wastewater
No full textIncreased antineoplastic drug concentrations in wastewater stem from ineffective treatment plants and increased usage. Although microrobots are promising for pollutant removal, they face hurdles in developing a superstructure with superior adsorption capabilities, biocompatibility, porosity, and pH stability. This study focused on adjusting the PVP concentration from 0.05 to 0.375 mM during synthesis to create a favorable CMOC structure for drug absorption. Lower PVP concentrations (0.05 mM) yielded a three-dimensional nanoflower structure of CaMoO4 and CuS nanostructures, whereas five-fold concentrations (0.25 mM) produced a porous structure with a dense CuS core encased in a transparent CaMoO4 shell. The magnetically movable and pH-stable COF@CMOC microrobot, achieved by attaching CMOC to cobalt ferrite (CoF) NPs, captured doxorubicin efficiently, with up to 57 % efficiency at 200 ng/mL concentration for 30 min, facilitated by electrostatic interaction, hydrogen bonding, and pore filling of DOX. The results demonstrated that DOX removal through magnetic motion showed superior performance, with an estimated improvement of 57% compared to stirring conditions (17 %). A prototype PDMS microchannel system was developed to study drug absorption and microrobot recovery. The CaMoO4 shell of the microrobots exhibited remarkable robustness, ensuring long-lasting functionality in harsh wastewater environments and improving biocompatibility while safeguarding the CuS core from degradation. Therefore, microrobots are a promising eco-friendly solution for drug extraction. These microrobots show promise for the selective removal of doxorubicin from contaminated wastewater. © 2024 Elsevier LtdFALSEsciescopu
Ultrasound-Assisted Photothermal Therapy (ULTRA-PTT) for the Treatment of Deep-Seated Tumors
No full textPhotothermal therapy (PTT) has garnered considerable attention as an attractive treatment tool for cancer due to precisely selective treatment and minimal side effects. The primary challenge of PTT, which hinders its widespread application, is the limited therapeutic depth. This limitation arises from optical scattering in biological tissues, causing inadequate heat distribution within the deep tissue. To overcome this challenge, ultrasound-assisted PTT (ULTRA-PTT) is proposed that leverages the temporary formation of gas bubbles induced by ultrasound within the light propagation path. These bubbles act as optical clearing agents, effectively reducing optical scattering in biological tissues. To facilitate ULTRA-PTT, a dedicated handpiece consisting of a ring-shaped ultrasound transducer and a laser delivery module is developed. In-vivo experiments show that ULTRA-PTT statistically outperforms conventional PTT in melanoma treatment, mostly due to its ability to deliver sufficient laser energy to deep-seated cancer cells. These findings underscore the potential of ULTRA-PTT to expand the clinical applications of PTT beyond local tumors occurring in superficial tissue. © 2024 Wiley-VCH GmbH.FALSEsciescopu
Animal model based on the heterogeneity of mossy cells in the hippocampal area and screening method for activity regulators of mossy cells
No full text본 발명은 해마 구역 내 모시세포의 이질성에 기반한 동물모델 및 모시세포 활성조절물질의 스크리닝 방법에 관한 것으로, 보다 구체적으로는 상기 모시세포의 하위 집단인 등쪽 모시세포가 불활성화된 인지 및 불안장애 동물모델, 상기 동물모델의 제조방법 및 상기 동물모델을 이용하여 인지 및 불안장애 치료 약물을 스크리닝하는 방법, 모시세포의 아형 구별용 마커 조성물 및 상기 마커의 발현 및 생리활성 수준 측정을 통한 모시세포 활성조절물질의 스크리닝 방법에 관한 것이다. 본 발명에 따르면, 모시세포는 구조적, 분자적 및 기능적 특성에서 중요한 차이를 나타내는 적어도 두 개의 별개 하위 집단인, 등쪽 모시세포 (dMC) 및 배쪽 모시세포 (vMC)로 분류되며, 모시세포 아형에 특이적인 유전자 발현 패턴을 나타내므로 상기 유전자들을 마커로 이용해 모시세포 아형을 구분하고 이의 활성을 특이적으로 조절하는 체내외 물질을 스크리닝하는데 이용할 수 있으며, 정서 및 인지 행동에서 기능적 이질성을 나타내어 등쪽 모시세포의 선택적 불활성화에 의해 인지장애 및 불안장애 표현형이 유도됨을 확인하였는바, 등쪽 모시세포의 불활성화를 통해 제조된 본 발명의 동물모델은 관련 질병의 기전 규명, 치료물질의 탐색, 진단법의 개발 등에 다양하게 활용될 수 있을 것으로 기대된다