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Accelerated Design of High-Efficiency Lead-Free Tin Perovskite Solar Cells via Machine Learning
No full textTin (Sn) perovskite solar cells (PSCs) are the most promising alternatives to lead (Pb) PSCs, which pose a theoretical limitation on efficiency and an environmental threat. However, Sn PSCs are still in the early stage of development in comparison with the conventional Pb PSCs, and still require a considerable amount of time and effort to obtain an optimum structure via manual trial-and-error methods. Herein, we propose a machine learning (ML) approach to accelerate the design of the optimized structure of Sn PSCs with high efficiency. The proposed method uses K-fold cross-validation-based deep neural networks, thus maximizing the prediction and recommendation accuracy with a limited amount of experimental data recorded for the Sn PSCs. Our approach establishes a new appropriate Sn-PSC design based on an ML recommendation algorithm. The validation experiment reveals a three times higher efficiency of the ML-designed Sn PSCs (5.57%) than that of those designed through unguided fabrication trials (avg. 1.72%)
Representing the Timbre of Traditional Musical Instruments Based On Contemporary Instrumental Samples Using DDSP
No full texthis project explores the potential of Differentiable Digital Signal Processing (DDSP) to represent and synthesize the timbre of five different notes of the Korean traditional musical instrument, Geo- mungo, using digital instrumental samples of the bass guitar, which has a similar mechanism to produce the sound. To evaluate the fea- sibility and quality of the digital recreation process, we compared hand-played Geomungo audio samples with digitally recreated au- dio samples using DDSP. The MFCC, spectral contrast, chroma features, and raw signal comparison, were used for assessment. Our findings show the possibility of applying DDSP to represent and synthesize the nuances of pitch and dynamics for expressive aspects of Geomungo???s five different notes effectively. We also pro- pose three audio features that can be used to evaluate the results quantitatively under the context of neural sound synthesis
Experimental investigation of thermal behavior of overfilled sodium heat pipe
No full textOperating limitations model of heat pipes are difficult to evaluate the effect of the charging amount of working fluid, which is one of the crucial factors in heat pipe performance of startup and maximum heat transfer. To reduce the knowledge gap on the effect of filling amount, the purpose of this paper is an investigation of the thermal behavior of excess liquid. Overfilled sodium heat pipe having about 260% filling ratio was fabricated and tested with the change of boundary and initial condition. Sodium heat pipe showed good isothermal characteristics that the temperature difference between evaporator and condenser reduced as the development of continuum flow until reaching operating limit condition. The characteristics of an overfilled heat pipe appear at power increased after the continuum flow fully developed to the condenser that sudden temperature rise about 100 & DEG;C in the overall heat pipe except the end region of the condenser where a continuous temperature about 50 & DEG;C drop occurs. Excess liquid moves toward the condenser end and forms the liquid pool and lessening the active condenser length which reduces the maximum heat transfer of heat pipe and induced the operating limitation. The re-sults showed that this phenomenon only occurs at high heat flux conditions as sufficient vapor flow is required to allow excess liquid to propagate to the condenser and determined the operating limitation of overfilled sodium heat pipe that continuous temperature rises as the liquid propagates to the end of the condenser rather than the abrupt rising such as dry out. However, the operating limitations occur sudden dry-out of the evaporator similar to the conventional results of liquid metal heat pipe when the liquid propagation did not occur. Compared to the entertainment limit model, there was a significant difference in the dry-out point of the experimental results with excessive liquid propagation. It was confirmed that the horizontal operation of overfilled heat pipe was in good agreement with the prediction of capillary limit model within 22.6% of the maximum error. & COPY; 2023 Elsevier Ltd. All rights reserved
Anomalous Temperature and Polarization Dependences of Photoluminescence of Metal-Organic Chemical Vapor Deposition-Grown GeSe2
No full textGermanium diselenide (GeSe2) is a 2D semiconductor with air stability, a wide bandgap, and anisotropic optical properties. The absorption and photoluminescence (PL) of single-crystalline 2D GeSe2 grown by metal-organic chemical vapor deposition and their dependence on temperature and polarization are studied. The PL spectra exhibit peaks at 2.5 eV (peak A) and 1.8 eV (peak B); peak A displays a strongly polarized emission along the short axis of the crystal, and peak B displays a weak polarization perpendicular to that of peak A. With increasing temperature, peak B shows anomalous behaviors, i.e., an increasing PL energy and intensity. The excitation energy-dependent PL, time-resolved PL, and density functional theory calculations suggest that peak A corresponds to the band-edge transition, whereas peak B originates from the inter-band mid-gap states caused by selenium vacancies passivated by oxygen atoms. The comprehensive study on the PL of single-crystalline GeSe2 sheds light on the origins of light emission in terms of the band structure of anisotropic GeSe2, making it beneficial for the corresponding optoelectronic applications
Emerging Technology of Nanofiber-Composite Hydrogels for Biomedical Applications
No full textHydrogels and nanofibers have been firmly established as go-to materials for various biomedical applications. They have been mostly utilized separately, rarely together, because of their distinctive attributes and shortcomings. However, the potential benefits of integrating nanofibers with hydrogels to synergistically combine their functionalities while attenuating their drawbacks are increasingly recognized. Compared to other nanocomposite materials, incorporating nanofibers into hydrogel has the distinct advantage of emulating the hierarchical structure of natural extracellular environment needed for cell and tissue culture. The most important technological aspect of developing "nanofiber-composite hydrogel" is generating nanofibers made of various polymers that are cross-linked and short enough to maintain stable dispersion in hydrated environment. In this review, recent research efforts to develop nanofiber-composite hydrogels are presented, with added emphasis on nanofiber processing techniques. Several notable examples of implementing nanofiber-composite hydrogels for biomedical applications are also introduced
Stretchable High-Resolution User-Interactive Synesthesia Displays for Visual-Acoustic Encryption
No full textMultifunctional displays, which have various functions in single-device systems without external circuits, are actively investigated as future human-machine interfaces owing to performability of unprecedented functions in compact design. However, their application is limited to visualize the mechanical/electrical signals in light. Herein, stretchable high-resolution multicolor synesthesia display, which can generate synchronized sound and light as input/output sources, is presented by transfer-printing. Transfer-printed emissive composite leads to display with enhanced optical performance and fine sound pressure level. Owing to inherent stretchability of the device, the synesthesia display can stably operate under static and dynamic deformation without distortion in sound relative to the input waveform. User-interactive synesthesia displays are demonstrated for visual-acoustic encryption, which facilitate advanced encryption, as well as multiplex quick response code that bridges multiple domains with a single device. This approach provides new directions for multifunctional displays, with potential applications in reinforced authentication
Catalytic CO2 Hydrogenation and Off-gas Upgrading Strategies
No full textThe steady increase of CO2 in the atmosphere owing to the excessive use of fossil fuels is seriously threatening the future of humankind by accelerating climate change. However, catalytic chemistry can turn this harmful greenhouse gas into a renewable source of carbon to provide an alternative feedstock for producing high-value hydrocarbon fuels, chemicals, and polymers as a carbon capture and utilization (CCU) strategy. Among the proposed CCU options, catalytic CO2 hydrogenation is attractive because the process is very similar to the well-established CO hydrogenation
Development of neutron detection systems at the NDPS of RAON
No full textThe Nuclear Data Production System (NDPS) at RAON has been built to produce nuclear data generated by the reactions induced by neutrons of tens of MeV. For the neutron Time-Of-Flight (TOF) measurement, neutron monitoring detectors based on a gas-filled Parallel Plate Avalanche Counter (PPAC) and a MICRO-MEsh-GASeous (MICROMEGAS) detector have been developed by the Rare Isotope Science Project (RISP) and Sungkyunkwan University (SKKU). These detectors have a neutron converter with a thin 232Th layer, which produces fission products due to fast neutrons. The PPAC achieved a 1 ns FWHM time resolution in a test with an 241Am ������ source and also showed good performance when tested with fast neutrons generated by a 45 MeV proton beam through the 9Be(p, n)9B reaction. Additionally, EJ-301, liquid scintillation detectors are assembled for the measurement of neutron flux with pulse shape discrimination capability. Slow charge signals as well as fast timing signals from the detectors will be processed for particle identification by a data acquisition (DAQ) system, located at a separate control room through 30 m long cables. Development of the detection system and the test results will be reported together with the on-site assembly status
The origin of overpotential in conversion-type cathode-material for potassium-ion batteries
No full textSchool of Energy and Chemical Engineering (Energy Engineering (Battery Science and Technology))clos
Development in Na/ZnFe204-Zeolite Hybrid Catalysts for Carbon Dioxide Conversion to Value- added Hydrocarbons
No full textSchool of Energy and Chemical Engineering (Chemical Engineering)clos