150 research outputs found
Sagnac interferometer for time-resolved magneto-optical measurements
No full text© 2022 Author(s).We introduce a time-resolved magneto-optical measurement technique based on a zero-area Sagnac interferometer. By replacing a continuous wave light source to a pulsed one, temporal resolution of hundreds of picoseconds is achieved. Because two lights passing through a Sagnac loop always travel the same optical path length, the interference from the phase modulation and Kerr rotation occurs in a pulse mode. For illustration of the apparatus, we present ferromagnetic resonance of a Permalloy film caused by a magnetic field pump. The instrument still possesses the favorable properties of a Sagnac interferometer, such as rejection of all the reciprocal effects, and shows 1μrad/Hz sensitivity at a 3 μW optical power in the pulse mode.11Nsciescopu
Magneto-optical measurements of mesoscopic Nb superconducting structures using a ferromagnetic metal indicator layer
No full text© 2022 Author(s).Imaging local magnetic fields produced by nano- and micrometer-scale superconductors has become a vital tool that can not only reveal crucial information on the vortex dynamics and order parameters of the superconducting materials but also visualize the working mechanism of superconducting devices made for quantum information. Here, we performed measurements of the magnetic field distributions of mesoscopic superconducting structures with various geometries by combining a thin ferromagnetic metal layer as a magneto-optical sensing element that responds to the environmental magnetic fields and a custom-made sensitive Sagnac interferometer. The sensitivity of the technique enables the observation of magnetic flux jumps due to individual vortex entries into nanostructured superconductors. In addition, with the control of incident power at a focused laser spot, we induce thermally driven movement of vortices that leaves a trace of a microscopic optical heating pattern.11Nsciescopu
Tailoring MnO2 nanodomains in organic-inorganic hybrid interfaces toward tunable hydrocarbon separation
No full textOrganic solvent nanofiltration offers an energy-saving alternative to distillation for hydrocarbon fractionation. Here, we introduce a simple and scalable method for fabricating novel organic-inorganic hybrid membranes from polybenzimidazole (PBI) and manganese oxide (MnO2), designed for the separation of complex hydrocarbons. Homogeneously integrated MnO2 domains, formed via oxidative interaction with imidazole moieties within the PBI matrix, create a rigid hybrid structure with enhanced molecular selectivity. By systematically tuning PBI concentration, KMnO4 dosage, and reaction time, we achieved membranes with low molecular weight cut-off (MWCO) as low as 266 g mol-1. Notably, these membranes surpassed the reported upper bound for toluene/ 1,3,5-triisopropylbenzene separation and demonstrated effective fractionation of complex hydrocarbon mixtures, such as naphtha, enriching the lighter fractions. This study clarifies the role of KMnO4 in PBI modification: rather than inducing direct N-N crosslinking as previously suggested, it facilitates the in situ generation of crystalline MnO2 domains that bolster membrane rigidity and molecular selectivity. These findings underscore the potential of hybrid PBI membranes as a practical platform for membrane-assisted crude oil fractionation and offer prospects for advanced energy-efficient separation strategies.
Optogenetic Modulation of TrkB Signaling in the Mouse Brain
No full textOptogenetic activation of receptors has advantages compared with chemical or ligand treatment because of its high spatial and temporal precision. Especially in the brain, the use of a genetically encoded light-tunable receptor is superior to direct infusion or systemic drug treatment. We applied light-activatable TrkB receptors in the mouse brain with reduced basal activity by incorporating Cry2PHR mutant, Opto-cytTrkB(E281A). Upon AAV mediated gene delivery, this form was expressed at sufficient levels in the mouse hippocampus (HPC) and medial entorhinal cortex (MEC) retaining normal canonical signal transduction by the blue light stimulus, even by delivery of noninvasive LED light on the mouse head. Within target cells, where its expression was driven by a cell type-specific promoter, Opto-cytTrkB(E281A)-mediated TrkB signaling could be controlled by adjusting light-stimulating conditions. We further demonstrated that Opto-cytTrkB(E281A) could locally induce TrkB signaling in axon terminals in the MEC-HPC. In summary, Opto-cytTrkB(E281A) will be useful for elucidating time- and region-specific roles of TrkB signaling ranging from cellular function to neural circuit mechanisms. © 2020 The Author(s). Published by Elsevier Ltd.11Nsciescopu
지능형 데이터마이닝을 이용한 터빈사이클 성능 분석기의 개발
No full text학위논문(박사) - 한국과학기술원 : 원자력및양자공학과, 2004.2, [ x, 131 p. ]In recent year, the performance enhancement of turbine cycle in nuclear power plants is being highlighted because of worldwide deregulation environment. Especially the first target of operating plants became the reduction of operating cost to compete other power plants. It is known that overhaul interval is closely related to operating cost Author identified that the rapid and reliable performance tests, analysis, and diagnosis play an important role in the control of overhaul interval through field investigation. First the technical road map was proposed to clearly set up the objectives. The controversial issues were summarized into data gathering, analysis tool, and diagnosis method. Author proposed the integrated solution on the basis of intelligent data mining techniques. For the reliable data gathering, the state analyzer composed of statistical regression, wavelet analysis, and neural network was developed. The role of the state analyzer is to estimate unmeasured data and to increase the reliability of the collected data. For the advanced performance analysis, performance analysis toolbox was developed. The purpose of this tool makes analysis process easier and more accurate by providing three novel heat balance diagrams. This tool includes the state analyzer and turbine cycle simulation code. In diagnosis module, the probabilistic technique based on Bayesian network model and the deterministic technique based on algebraical model are provided together. It compromises the uncertainty in diagnosis process and the pin-point capability. All the modules were validated by simulated data as well as actual test data, and some modules are used as industrial applications.
We have a lot of thing to be improved in turbine cycle in order to increase plant availability. This study was accomplished to remind the concern about the importance of turbine cycle and to propose the solutions on the basis of academic as well as industrial needs.한국과학기술원 : 원자력및양자공학과
Effects of surface air injection on the air stability of superhydrophobic surface under partial replenishment of plastron
No full textFrictional drag reduction using a superhydrophobic (SHPo) surface has attracted great attention due to its potential for practical application. Air plastron (i.e., pockets) trapped between structures in a submerged SHPo surface serves a crucial role in the drag reduction effect. However, the air plastron on the SHPo surface can easily be depleted by various factors, resulting in the deterioration of the drag reduction performance. This study proposed a surface air injection method to resolve the depletion problem and explored its effect on the enhancement of the air stability of the SHPo surface as a controllable strategy under partial replenishment conditions in which the replenishment rate is less than the depletion rate. An air injection layer is added to a ridged multi-layered SHPo (ML-SHPo) surface to supply air through the surface. The dynamic behavior of air plastron on the surface is directly visualized by an x-ray imaging technique. The temporal evolution of depletion length on the ridged ML-SHPo surface is monitored under laminar flows to understand the underlying basic physics of the enhanced air stability caused by surface air injection. The depletion rate of air plastrons on SHPo surfaces depended on the nondimensional air injection rate (C q). The dynamic behavior in the air depletion regime is closely associated with flow condition and C q. The stability of air plastrons is enhanced by 12%-87% as the C q value increases. In addition, a simple scaling relationship between the depletion rate and C q is proposed to predict the depletion rate of air plastrons (longevity) on ridged SHPo surfaces. © 2022 Author(s).11Nsciescopu
Surface Passivation of CdSe Quantum Dots in All Inorganic Amorphous Solid by Forming Cd1-xZnx Se Shell
No full textCdSe quantum dots (QDs) doped glasses have been widely investigated for optical filters, LED color converter and other optical emitters. Unlike CdSe QDs in solution, it is difficult to passivate the surface defects of CdSe QDs in glass matrix, which strongly suppress its intrinsic emission. In this study, surface passivation of CdSe quantum dots (QDs) by Cd1-xZnx Se shell in silicate glass was reported. An increase in the Se/Cd ratio can lead to the partial passivation of the surface states and appearance of the intrinsic emission of CdSe QDs. Optimizing the heat-treatment condition promotes the incorporation of Zn into CdSe QDs and results in the quenching of the defect emission. Formation of CdSe/ Cd1-xZnx Se core/graded shell QDs is evidenced by the experimental results of TEM and Raman spectroscopy. Realization of the surface passivation and intrinsic emission of II-VI QDs may facilitate the wide applications of QDs doped all inorganic amorphous materials. ? The Author(s) 2017.114Ysciescopu
All-fiber-photonic sub-10(-14)-level comb-line stabilization
No full textWe demonstrate a fiber delay line-based direct comb-line stabilization with 6x10(-15) frequency instability within 1 s. Two combs could be simultaneously stabilized to a single fiber delay-line with similar to 1-Hz relative linewidth and similar to 20-Hz absolute linewidth. (C) 2020 The Author(s
High entropy oxides-exploring a paradigm of promising catalysts: A review
No full textThis review presents the structural elements and discusses the great potential of high entropy oxides (HEO) as promising catalysts. A critical comparison is provided with the medium and low entropy metal oxides in terms of the important functionality of HEO to exhibit higher oxygen mobility and withhold high population of oxygen vacancies as well as leading to high metal dispersion. This review study critically compares the performance of the thermal, electro- and photo- high entropy oxides catalysts with the conventional metal oxides and demonstrates their superiority over them while discussing the governing characteristics of HEO. The HEO complex structure is highlighted using ab initio calculations on understanding and tuning their electronic/structural properties. Catalysts’ design criteria and direction in the studies of the HEO as catalysts for energy and sustainability are proposed. © 2021 The Author
Optogenetic activation of intracellular antibodies for direct modulation of endogenous proteins.
No full text© 2019, The Author(s), under exclusive licence to Springer Nature America, Inc.Intracellular antibodies have become powerful tools for imaging, modulating and neutralizing endogenous target proteins. Here, we describe an optogenetically activated intracellular antibody (optobody) consisting of split antibody fragments and blue-light inducible heterodimerization domains. We expanded this optobody platform by generating several optobodies from previously developed intracellular antibodies, and demonstrated that photoactivation of gelsolin and β2-adrenergic receptor (β2AR) optobodies suppressed endogenous gelsolin activity and β2AR signaling, respectively11Nsci
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