2,699 research outputs found
High-Efficiency Quantum Dot Permeable Electrode Light-Emitting Triodes for Visible Light Communications and on-Device Data Encryption
No full textVisible-light communication (VLC) is a promising technology for alleviating data traffic and spectrum allocation problems. Traditional optoelectronic devices such as light-emitting diodes (LEDs) are crucial components of VLC systems. However, two-terminal devices are limited in their functionality and integration capabilities. Thus, a third permeable electrode (PE) is incorporated for high-efficiency quantum-dot PE light-emitting triodes (PeLETs), with a maximum external quantum efficiency of 17.4% and luminance exceeding 29,000 cd m-2. Then, we elucidate the interplay between the resistor-capacitor circuit and the charge injection process using transient electroluminescence measurements. The expanded functionalities allow the simultaneous modulation of two input data streams within a single device. The PeLETs enhance data throughput and transmission capacity through dual-channel communication. Furthermore, on-device data encryption is achieved using the concept of interference in the data transmission process. Single-device data modulation using PeLETs provides a novel concept for on-device data encryption for next-generation, highly secure VLC systems.
Direct Optical Lithography of Colloidal InP-Based Quantum Dots with Ligand Pair Treatment
No full textDirect optical lithography presents a promising patterning method for colloidal quantum dots (QDs). However, additional care needs to be taken to prevent deterioration of the optical properties of QDs upon patterning, especially for InP-based QDs. This study proposes an efficient method for high-resolution patterning of InP-based QDs using a photoacid generator while preserving their optical properties. Specifically, our solid-state ligand exchange strategy, replacing chloride ligands with long-chain amine/carboxylate pair ligands, successfully recovered the photoluminescence quantum yield (PLQY) of the patterned InP-based QD films to similar to 67% of the original PLQY. Upon examination of the origins of the PLQY reduction during patterning, we concluded that the formation of deep traps caused by the exchanged chloride ligands was the primary cause. Finally, we fabricated high-resolution (feature size: 1 mu m), multicolored patterns of InP-based QDs, thereby demonstrating the potential of the proposed patterning method for next-generation high-resolution displays and optoelectronic devices.
Progress and Prospects of Nanoscale Emitter Technology for AR/VR Displays
No full textAugmented reality (AR) and virtual reality (VR) are emerging interactive technologies that realize the "metaverse," leading to a totally new digital interactive experience in daily life in various aspects. In order to provide users with a more immersive experience, displays for AR/VR have rapidly evolved to achieve high resolutions and a large color gamut on small panels. Recently, nanoscale light emitters such as quantum dots (QDs) and metal halide perovskites (MHPs) with high photoluminescence quantum efficiency and color purity levels have garnered much attention as color conversion materials in AR/VR displays. However, the low material stability and the absence of a high-resolution patterning process that does not impair the optical properties of nanoscale emitters act as obstacles preventing the realization of high-resolution AR/VR displays. Here, the state-of-the-art technologies constituting current AR/VR devices are reviewed from an industrial point of view and the recent progress in QD and MHP emitter technologies are discussed, including their basic structural properties, synthesis strategies to enhance the stability, advanced patterning technologies, down-conversion and light-emitting diode applications. Based on the review, the authors' perspective on future research directions of nanoscale emitters for next-generation AR/VR displays is presented.N
Stimuli-Responsive Surface Ligands for Direct Lithography of Functional Inorganic Nanomaterials
No full textConspectus Colloidal nanocrystals (NCs)have emerged as a diverse class ofmaterials with tunable composition, size, shape, and surface chemistry.From their facile syntheses to unique optoelectronic properties, thesesolution-processed nanomaterials are a promising alternative to materialsgrown as bulk crystals or by vapor-phase methods. However, the integrationof colloidal nanomaterials in real-world devices is held back by challenges in making patterned NC films with the resolution, throughput, andcost demanded by device components and applications. Therefore, suitableapproaches to pattern NCs need to be established to aid the transitionfrom individual proof-of-concept NC devices to integrated and multiplexedtechnological systems. In this Account, we discuss the developmentof stimuli-sensitivesurface ligands that enable NCs to be patterned directly with goodpattern fidelity while retaining desirable properties. We focus onrationally selected ligands that enable changes in the NC dispersibilityby responding to light, electron beam, and/or heat. First, we summarizethe fundamental forces between colloidal NCs and discuss the principlesbehind NC stabilization/destabilization. These principles are appliedto understanding the mechanisms of the NC dispersibility change uponstimuli-induced ligand modifications. Six ligand-based patterningmechanisms are introduced: ligand cross-linking, ligand decomposition,ligand desorption, in situ ligand exchange, ion/ligandbinding, and ligand-aided increase of ionic strength. We discuss examplesof stimuli-sensitive ligands that fall under each mechanism, includingtheir chemical transformations, and address how these ligands areused to pattern either sterically or electrostatically stabilizedcolloidal NCs. Following that, we explain the rationale behind theexploration of different types of stimuli, as well as the advantagesand disadvantages of each stimulus. We then discuss relevantfigures-of-merit that should be consideredwhen choosing a particular ligand chemistry or stimulus for patterningNCs. These figures-of-merit pertain to either the pattern quality(e.g., resolution, edge and surface roughness, layer thickness), orto the NC material quality (e.g., photo/electro-luminescence, electricalconductivity, inorganic fraction). We outline the importance of theseproperties and provide insights on optimizing them. Both the patternquality and NC quality impact the performance of patterned NC devicessuch as field-effect transistors, light-emitting diodes, color-conversionpixels, photodetectors, and diffractive optical elements. We alsogive examples of proof-of-concept patterned NC devices and evaluatetheir performance. Finally, we provide an outlook on further expandingthe chemistry of stimuli-sensitive ligands, improving the NC patternquality, progress toward 3D printing, and other potential researchdirections. Ultimately, we hope that the development of a patterningtoolbox for NCs will expedite their implementation in a broad rangeof applications.
의존구조를 가진 단순복합위험모형
No full text학위논문 (석사)-- 서울대학교 대학원 : 통계학과, 2016. 8. Myunghee Cho Paik.There have been fewer trials to address the claim severity in the development of optimal bonus-malus system (BMS), while the claim frequency has been dealt with a lot. In this article, the generalized linear mixed model (GLMM) was incorporated to address the severity, frequency, and their dependency simultaneously with 5 years insurance panel data. Also, estimated individual random effect coefficient from training set and past claim was utilized as a predictor of future loss. From the result of analysis, it was revealed that GLMM had the better fit than its alternatives including simple generalized linear model, dependency between the frequency and severity was significant, and estimated random effect coefficient predicted the future loss better as the length of training set increased. These results provide the rationale to reflect both the past frequency and past severity to construct the optimal BMS, and considering dependence between frequency and severity in the derivation of motor insurance premium.1.Introduction 1
2.Literature review 3
2.1.The Rationale of Bonus-Malus System in Auto Insurance 3
2.2.Designing optimal BMS with past frequency and severity 5
2.3.Individual effects and dependency between frequency and severity 6
3.Data and Methodology 8
3.1.Data Description 8
3.2.Proposed Model 9
4.Model Comparison and Empirical Analysis 11
4.1.Frequency 11
4.2.Severity 14
5.Prediction 15
5.1.Frequency 16
5.2.Severity 19
6.Dependency between the Frequency and Severity 21
7.Conclusion 23
Appendix 24
References 33
국문 초록 35Maste
Erratum: 3D bioprinted in vitro secondary hyperoxaluria model by mimicking intestinal-oxalatemalabsorption-related kidney stone disease (Applied Physics Reviews (2022) 9 (041408) DOI: 10.1063/5.0087345)
No full text© 2023 Author(s).This article was originally published online on 21 November 2022 with an incorrect affiliation identifier for author Dong-Woo Cho. It is correct as it appears above. All online versions of this article were corrected on 23 November 2022. AIP Publishing apologizes for this error.11Nsciescopu
Unimodality of Betti numbers for Hamiltonian circle actions with index-increasing moment Maps
No full textThe unimodality conjecture posed by Tolman in [L. Jeffrey, T. Holm, Y. Karshon, E. Lerman and E. Meinrenken, Moment maps in various geometries, http://www.birs.ca/workshops/2005/05w5072/report05w5072.pdf] states that if (M,ω) is a 2n-dimensional smooth compact symplectic manifold equipped with a Hamiltonian circle action with only isolated fixed points, then the sequence of Betti numbers {b0(M),b2(M),...,b2n(M)} is unimodal, i.e. bi(M) ≤ bi+2(M) for every i < n. Recently, the author and Kim [Y. Cho and M. Kim, Unimodality of the Betti numbers for Hamiltonian circle action with isolated fixed points, Math. Res. Lett. 21(4) (2014) 691-696] proved that the unimodality holds in eight-dimensional case by using equivariant cohomology theory. In this paper, we generalize the idea in [Y. Cho and M. Kim, Unimodality of the Betti numbers for Hamiltonian circle action with isolated fixed points, Math. Res. Lett. 21(4) (2014) 691-696] to an arbitrary dimensional case. We prove the conjecture in arbitrary dimension under the assumption that the moment map H : M → R is index-increasing, which means that ind(p) < ind(q) implies H(p) < H(q) for every pair of critical points p and q of H, where ind(p) is the Morse index of p with respect to H. © World Scientific Publishing Company1111sciescopu
π-공액 다중 결합 첨가제를 활용한 청색 페로브스카이트 전계 발광 소자 색 안정성 향상에 대한 연구
No full text학위논문(석사) - 한국과학기술원 : 신소재공학과, 2025.2,[iv, 39 p. :]Metal halide perovskites are promising for next-generation LEDs due to their high PLQY, defect tolerance, and color tunability. However, blue perovskite LEDs face challenges from defect-induced instability and phase segregation, which pose a significant bottleneck for achieving full-color displays. While urea-based passivation, a common strategy using Lewis base passivation, has been widely studied, its efficiency is limited by the reduced availability of the nitrogen lone pair. This study explores carbamate-based passivation as an alternative to urea-based passivation to enhance device performance. We demonstrate that benzyl carbamate (BC) strongly multi-binds with defect sites containing under-coordinated Pb ions through all of its Lewis base functional groups. The multi-site coordination enhances PLQY, film crystallinity, and stability, while suppressing halide segregation. In contrast, benzyl urea (BU) exhibits weaker coordination due to the reduced accessibility of the nitrogen lone pair caused by its resonance structure and strong intermolecular interactions. These findings address a critical gap in urea-based passivation, providing a deeper understanding of how molecular structure and intermolecular interactions influence coordination efficiency. This research highlights the potential of carbamate group passivation for enhancing the stability and performance of perovskite LEDs, offering valuable insights for the development of advanced materials for optoelectronic applications.한국과학기술원 :신소재공학과
Systems biology for reverse aging
No full textCellular senescence is an irreversible and permanent cell cycle arrest in response to internal and external stresses. Its unresponsiveness to growth factor signals distinguishes it from a potentially reversible state, quiescence. Cellular senescence can inhibit tumor development by blocking proliferation of damaged cells, but as senescent cells become accumulated in a tissue, they can contribute to the promotion of agerelated diseases such as cancer by secreting inflammatory cytokines [1]. © 2021 Cho et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
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