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Current-Driven Collective Control of Helical Spin Texture in van der Waals Antiferromagnet
No full textElectrical control of quantum magnetic states is essential in spintronic science. Initial studies on the ferromagnetic state control were extended to collinear antiferromagnets and, more recently, noncollinear antiferromagnets. However, electrical control mechanisms of such exotic magnetic states remain poorly understood. Here, we report the first experimental and theoretical example of the current control of helical antiferromagnets, arising from the competition between collinear antiferromagnetic exchange and interlayer Dzyaloshinskii-Moriya interaction in new van der Waals (vdW) material Ni1/3NbS2. Due to the intrinsic broken inversion symmetry, an in-plane current generates spin-orbit torque that, in turn, interacts directly with the helical antiferromagnetic order. Our theoretical analyses indicate that a weak ferromagnetic order coexists due to the Dzyaloshinskii-Moriya interaction, mediating the spin-orbit torque to collectively rotate the helical antiferromagnetic order. Our Ni1/3NbS2 nanodevice experiments produce current-dependent resistance change consistent with the theoretical prediction. This Letter widens our understanding of the electrical control of helical antiferromagnets and promotes vdW quantum magnets as interesting material platforms for electrical control.FALSEsciescopu
Global decomposition of networks into multiple cores formed by local hubs
No full textNetworks are ubiquitous in various fields, representing systems where nodes and their interconnections constitute their intricate structures. We introduce a network decomposition scheme to reveal multiscale core-periphery structures lurking inside, using the concept of locally defined nodal hub centrality and edge-pruning techniques built upon it. We demonstrate that the hub-centrality-based edge pruning reveals a series of breaking points in network decomposition, which effectively separates a network into its backbone and shell structures. Our local-edge decomposition method iteratively identifies and removes locally least connected nodes, and uncovers an onionlike hierarchical structure as a result. Compared with the conventional k-core decomposition method, our method based on relative information residing in local structures exhibits a clear advantage in terms of discovering locally crucial substructures. As an application of the method, we present a scheme to detect multiple core-periphery structures and the decomposition of coarse-grained supernode networks, by combining the method with the network community detection.TRUEsciescopu
Stress Simulation of CFET Inverters with Unmerged Sige S/D and Wrap-Around Contact
No full textStress profiles inside CFET inverters are analyzed with our in-house process emulator equipped with a newly developed stress module. In the conventional structure, the PMOS channel exhibits a peak compressive stress of -1.9 GPa, whereas the NMOS channel exhibits only +0.3 GPa tensile stress. In the PMOS, the horizontal defects lead to a 19 % reduction in channel stress and vertical defects induce tensile stress in the channel. Employing the unmerged SiGe S/D, the peak stress of NMOS is enhanced to + 1. 2 ~ GPa. Adopting the wrap-around contact in the PMOS lowers its channel stress by 19 % compared to the conventional contact structure. These findings offer clear guidelines for stress-engineering optimized CFET architectures. © 2025 IEEE
Development of Novel Body Center of Pressure Estimation System Based on Tactile Sensor and Deep Learning Models
No full textThe Center of Pressure (CoP) is utilized as an essential indicator for assessing the body’s balance. CoP reflects the state of balance and is important in evaluating balance ability and predicting fall risk. Existing systems are too expensive, less accurate in dynamic conditions, or have limited measurement ability, which is for only the foot’s CoP without fully reflecting the overall body balance. Thus, this study proposes a novel system using Tactile sensors and a deep learning model for less cost and accurately estimating dynamic body CoP. The performance of the suggested CNN-Bi-LSTM model was compared with existing foot CoP estimation models, CNN-LSTM and Bi-LSTM. Model performance was validated using the Leave-One-Out Cross-Validation (LOOCV) method and evaluated with Root-Mean-Squared Error (RMSE) and R² coefficient. The experimental results showed that the CNN-Bi-LSTM model achieved the best performance, with an average RMSE of 7.09 mm in the ML direction and 4.69 mm in the AP direction, and an average R² of 0.99. In comparison, the CNN-LSTM and Bi-LSTM models recorded RMSE values of 11.59 mm and 25.52 mm in the ML direction, and 8.81 mm and 10.90 mm in the AP direction, respectively. Additionally, the RMSE difference value between ML (medio-lateral) and AP (Antero-posterior) was shown to be smaller compared to previous studies on estimating the foot CoP. This result highlights the effectiveness of the CNN-Bi-LSTM model in capturing both spatial and temporal features, surpassing traditional methods and previous models in dynamic conditions. Future research will focus on expanding the system and conducting clinical trials for gait CoP analysis.FALSEkc
Novel state of charge estimation of lithium-ion batteries using empirical neural tangent kernel and unscented Kalman filter
No full textAccurate state of charge (SoC) estimation is essential for optimizing the performance and safety of rechargeable batteries. Existing methods often struggle with dynamic battery conditions. This study proposes a hybrid approach that combines empirical neural tangent kernel (eNTK) regression with an unscented Kalman filter (UKF) for enhanced SoC estimation. The proposed method identifies the battery model using eNTK regression, splits the obtained regression model to construct prediction and measurement models, and integrates them into a UKF framework. Extensive validation over various driving cycles, temperature, and state of health conditions demonstrate significant enhancements in SoC estimation accuracy, reducing mean square error by an average of 75.35% and the average standard deviation by an average of 47.11%, compared to the EKF using the 2RC model, which incorporates hysteresis characteristics. © 2025 Elsevier LtdFALSEsciescopu
Numerical investigation of effect of Si separator in bottom dielectric isolation forksheet FETs via in-house TCAD process emulator and device simulator
No full textIn this work, we investigate the effect of a Si separator on the fabrication and performance of a bottom dielectric isolation (BDI) forksheet field-effect transistor (FSFET) using our in-house technology computer-aided design process emulator and device simulator. The process emulator is implemented with a three-dimensional multilevel-set method to emulate the BDI FSFET fabrication under various process conditions. Our results demonstrate that the addition of a Si separator is a plausible option for the BDI FSFET. To verify this conclusion from an electrical performance perspective, we simulate the electrical characteristics of the devices using our in-house device simulator. The device structures generated from the process emulator are directly used for the device simulation. The device simulation results confirm that incorporating a Si separator remains the optimal choice, even when considering the device performance.FALSEsciescopu
Effectiveness of a Karaoke-Based Digital Therapeutic in Mild Cognitive Impairment: A Randomized, 12-Week Pilot Trial
No full textObjective The aim of the study is to evaluate the efficacy of a karaoke-based digital therapeutic program (CogniSong) in patients with Methods In a 12-week single-center, assessor-blinded randomized controlled trial, 36 patients with MCI were randomly assigned to either the CogniSong digital therapeutics (DTx) group (n=18) or standard treatment group (n=18). The intervention group underwent daily 30-minute karaoke game-based cognitive training sessions via a mobile application. The primary outcome was the change in Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) total score from baseline to week 12. Secondary outcomes included RBANS subdomain index scores, the Seoul-Instrumental Activities of Daily Living, 17-item Hamilton Depression Rating Scale, Results The DTx group showed a significantly greater improvement in RBANS total score compared to standard treatment group (mean change +5.9 points vs. -0.2 points, p=0.041). However, there were no significant between-group differences in RBANS subdomain scores or secondary outcomes such as daily functioning, mood, neuropsychiatric symptoms, or global clinical status. Conclusion In this randomized controlled trial, a karaoke-based DTx appeared feasible and effective in enhancing global cognition in MCI. The findings support its potential as a complementary intervention for cognitive improvement in MCI patients.TRUEsciessciscopuskc
A study on solid state synthesis of electrocatalysts assisted by resonant acoustic mixing for electrochemical reactions
No full textGreen and scalable synthesis techniques for producing highly dispersed supported metal nanocatalysts (SMNCs) are essential for industrial heterogeneous catalysis. Traditional liquid-phase methods to create nanosized SMNCs often rely on organic capping agents and low metal loading to prevent nanoparticle aggregation, yet these requirements hinder practical, large-scale production. Supported metal nanoparticles are highly sought after for their exceptional activity, stability, and reusability in electrochemical applications, making it critical to develop more efficient and scalable synthesis methods. Conventional material synthesis processes tend to consume substantial time and energy and generate waste solvents, posing environmental challenges.
Mechanochemical synthesis provides a promising alternative as an environmentally friendly and scalable approach. This method, applied in fields such as metallurgy, mineral processing, and organic synthesis, has gained renewed interest in producing various nanomaterials, including organic, inorganic, and hybrid materials. Mechanochemistry proves particularly effective in creating highly porous carbons, metal-organic frameworks (MOFs), and covalent organic frameworks (COFs). Ball milling, a mechanochemical process, has also been used to produce ordered coordination polymers and mesoporous carbons. Today, mechanochemistry is recognized as a versatile and powerful tool for synthesizing a wide range of materials, particularly those used in adsorption, catalysis, and energy storage.
However, there are still challenges for synthesis of SMNCs in that they have limitations; possibility of oxidation, time-consuming, aggregation of particles and limited elements, etc. To solve those limitations, this study introduces an innovative solid-state synthesis method utilizing resonant acoustic mixing (RAM) with ball, a technique that enables easy, eco-friendly metal nanoparticle production without organic solvents. RAM employs acoustic energy to facilitate substance mixing, using ultrasound waves to increase particle movement and enhance blending efficiency. Known for its adaptability and energy efficiency, RAM supports improved product quality, operational efficiency, and reduced manufacturing costs, making it highly suitable for sustainable, large-scale applications.DoctorAbstract ⅴ
Contents ⅶ
List of tables ⅸ
List of figures ⅹ
Chapter I. INTRODUCTION 1
1.1. Background 1
1.2. Overview of the nanoparticle preparation methods 4
1.3. Recent developments of solid-state synthesis method 7
1.4. Resonant acoustic mixing 13
Chapter Ⅱ. PREPARATION OF THIOL-DECORATED Ag NANOPARTICLES ON N-DOPED CARBON THROUGH RESONANT ACOUSTIC MIXING FOR ELECTROCHEMICAL CO2 REDUCTION 19
2.1. Introduction 19
2.2. Experimental 24
2.3. Results and discussion 29
2.4. Conclusion 51
Chapter Ⅲ. FACILE PREPARATION OF CORE-SHELL Ru@Ir/C CATALYST AS A BIFUNCTIONAL ELECTROCATALYST FOR REVERSAL-TOLERANT ANODE IN POLYMER ELECTROLYTE MEMBRANE FUEL CELL 52
3.1. Introduction 52
3.2. Experimental 57
3.3. Results and discussion 63
3.4. Conclusion 93
Chapter Ⅳ. INVESTIGATION OF HIGH ENTROPY ALLOY NANOPARTICLES ASSISTED BY RESONANT ACOUSTIC MIXING FOR OXYGEN REDUCTION REACTION 94
4.1. Introduction 94
4.2. Experimental 98
4.3. Results and discussion 102
4.4. Conclusion 118
Chapter Ⅴ. SUMMARY 119
REFERENCES 123
Acknowledgement 132
CURRICULUM VITAE 133
Education 13
Exciplex Formation in Non-linked and Peptoid- conjugated Systems with Experimental and Computational Approaches Suhyun Park College of Natural Sciences
No full textThis thesis presents a comprehensive investigation of exciplex photophysics, progressing from fundamental studies in non-linked systems to complex dynamics in peptoid-conjugated system, ultimately establishing foundations for quantum information science applications. The research begins by revisiting Weller's classical framework for exciplex formation through systematic studies of anthracene (Ant) as electron acceptor with N,N-dimethylaniline (DMA) derivatives as donors in cyclohexane. By integrating steady-state and time-resolved spectroscopy with long-range corrected density functional theory (LC-DFT), this work reveals that the C–N rotational angle (φ) of the dimethylamine group critically modulates both the HOMO energy and its spatial distribution, thereby controlling photoinduced electron transfer (PET) rates. Notably, while electrochemical redox potentials follow the Rehm-Weller plot on logarithmic scales, they fail to explain specific cases on linear scales. LC-DFT calculations successfully rationalize these discrepancies, demonstrating that ortho-methyl substituted donors NN2 and NN26 exhibit restricted PET due to steric hindrance forcing twisted conformations, with only ~5% of NN2 molecules achieving the quasi-planar geometry required for PET while NN26 shows complete PET suppression. Furthermore, NN4 exhibits the fastest PET rate despite lower HOMO energy than julolidine due to extended HOMO distribution upon rotation. Vibrationally resolved emission spectra simulations using TD-DFT accurately reproduce experimental exciplex emissions, revealing that emission intensity depends on the donor's contribution to the exciplex HOMO. Building upon these fundamental insights, the study explores peptoid-conjugated exciplex systems featuring Ant and DMA in designed off-facial (i,i+2)-Ac and co-facial (i,i+3)-Ac arrangements on 9-mer peptoid scaffolds. Despite DFT-optimized ground-state structures indicating more favorable geometry for (i,i+3)-Ac with ~5 Å D-A distance versus ~14 Å for (i,i+2)-Ac, femtosecond transient absorption (fsTA) and fluorescence up- conversion (FLUP) unexpectedly reveal faster PET kinetics for the (i,i+2)-Ac system. This counterintuitive behavior persists even in high-viscosity solvents, ruling out simple scaffold reorganization mechanisms. In this context, low-temperature (77 K) experiments provide direct evidence for peptoid conformational heterogeneity, which is the other hypothesis for faster PET in (i,i+2)-Ac system. At low- temperature, (i,i+2)-Ac exhibits enhanced exciplex emission and efficient PET in frozen states, while (i,i+3)-Ac shows virtually no PET. TD-DFT calculations reveal that exciplex formation in (i,i+2)-Ac requires significant deviation in phi (φ) and psi (ψ) angles of the Ant-bearing residue from ground state of (i,i+2)-Ac calculated by DFT, not cis/trans isomerization. Molecular dynamics simulations using CGenFF-based peptoid force fields confirm a heterogeneous φ/ψ distribution in (i,i+2)-Ac ground states, with a significant population pre-organized for exciplex formation, contrasting with the more symmetric energy landscape of (i,i+3)-Ac. Extending beyond electron transfer systems, the research explores peptoid-conjugated chromophore- radical architectures featuring pyrene and BDPA (1,3-Bis(diphenylene)-2-phenylallyl). These systems exhibit red- shifted emission, ground-state complexation, and weak but detectable magnetic field effects (~0.15%), suggesting radical-exciplex formation potentially involving quartet states. To enable detailed spin dynamics investigations, a continuous-wave electron paramagnetic resonance (cwEPR) spectrometer was successfully constructed, featuring an X-band IF bridge, loop-gap resonator, high-resolution teslameter with analog feedback control, and custom cryostat for future time-resolved EPR studies. In summary, this work presents a thorough investigation of exciplex behavior, employing both experimental and computational methodologies. Starting with a detailed re-evaluation of photoinduced electron transfer in fundamental non-linked donor-acceptor systems which clarified the critical role of molecular conformation over classical electrochemical interpretations, the research progressed to uncover how peptoid structural heterogeneity dictates linked exciplex photophysics. The foundational knowledge and instrumental advances achieved, including the custom-built continuous-wave electron paramagnetic resonance spectrometer, open avenues for developing peptoid scaffolds for advanced photochemical applications and investigating their potential in quantum information science. List of ContentsDoctorAbstract
List of Contents
List of Figures
List of table
I. Introduction 1
1.1. Exciplex 1
1.1 1. Definition 1
1.1.2. History 2
1. 2. Ultrafast Time-Resolved Spectroscopy 5
1.2.1. Femtosecond Transient Absorption (fsTA) 5
1.2.2. Fluorescence Up-conversion (FLUP) 10
1.2.3. Collinear Optical Parametric Amplifier 14
1. 3. Density Functional Theory (DFT) 18
1.3.1. Brief Principle 18
1.3.2. Time-Dependent DFT (TD-DFT) 19
1.3.3. Long-Range-Corrected Scheme 20
1.3.4. Emission Simulation with Vertical and Adiabatic Hessian 21
1.3.5. Corrected Linear Response (cLR) 23
1.4. Conformational Study for Peptoid by MD simulations 24
1.4.1. Definition of Peptoid 24
1.4.2. Conformation of Peptoid 25
1.4.3. Brief Principle of Molecular Dynamics Simulations 26
1.4.4. Force Field for Peptoid 26
1.4.5. Enhanced Sampling 27
1.5. Electron Parmagnetic Resonance (EPR) 30
1.5.1. Brief Principle 30
1.5.2. Applications 32
1.6. Research Story Line 33
1.7. References 35
II. Comprehensive Insights into Exciplex Behavior in Nonpolar Media: Revisiting Weller’s Framework with Molecular Conformation 43
2.1. Abstract 43
2.2. Introduction 44
2.3. Methods 46
2.3.1. Materials 46
2.3.2. Spectroscopy 46
2.3.3. Electrochemistry 47
2.3.4. Computational Details 47
2.4. Results And Discussions 50
2.4.1. Steady-State Spectroscopy 50
2.4.2. Stern–Volmer Plots 51
2.4.3. Rehm–Weller Plots 52
2.4.4. DFT Results and Effect of C–N Bond Rotation on PET 55
2.4.5. TD-DFT Results and Emission Simulation 61
2.5. Conclusion 65
2.6. References 66
2.7. Supporting Information 73
2.7.1. Results of spectroscopic experiments 73
2.7.2. Results of electrochemical experiments 83
2.7.3. Comparison between electrochemical HOMO and computational HOMO 85
2.7.4. Potential energy surfaces (PES) for C–N rotational angle of donors 87
2.7.5. HOMO distribution of donors 94
2.7.6. Potential energy surfaces of exciplexes for Ant/Donor pairs 101
2.7.7. Simulation for exciplex emission for Ant/Donor pairs and MO diagrams 104
2.7.8. Coordination of optimized donors and exciplexes 108
2.7.9. References for Supporting Information 120
III. Unexpected Ultrafast Photoinduced Electron Transfer of Peptoid-Conjugated Off-facial Exciplex System 122
3.1. Introduction 122
3.2. Experimental Methods 123
3.3. Results and Discussions 125
3.4. Summary 129
3.5. Supporting Information 130
3.6. References 135
IV. Direct Evidence for Heterogeneity of Peptoid via Characteristic of Exciplex System 136
4.1. Introduction 136
4.2. Experimental Methods 139
4.3. Results and Discussions 141
4.4. Summary 147
3.5. Supporting Information 148
3.6. References 153
V. Peptoid-Conjugated Chromophore-Radical Exciplex System and Set-up for Continuous-wave Electron Paramagnetic Resonance (cwEPR) 156
5.1. Introduction 156
5.2. Experimental Methods 157
5.3. Results and Discussions 160
5.4. Summary 164
5.5. References 16