This study aims to develop a prediction model using machine learning to predict gear whine noise using the inspection data of gear tooth and noise bench test data in semi-anechoic chambers. To secure ...the reliability of the collected dataset, we select features that affect the prediction results by the lasso regression method. Based on the selected features, the prediction model was developed according to the characteristics of gear teeth under each vehicle’s driving load condition. Random forest, decision tree, gradient boosting, extreme gradient boosting (XGB), light gradient boosting model algorithm, and the statistical regression method called ordinary least squares (OLS) are used to construct the prediction models. In addition, the performance of the machine-learning-based models and models using conventional statistical methods are compared. Prediction error reduction rate and prediction performance improvement rate are used to assess the performance of each model. The prediction model using the XGB algorithm exhibits the best performance. The obtained results demonstrate that the machine-learning-based prediction model can be used to predict gear whine noise with higher accuracy than OLS.
Indium phosphide (InP) quantum dots (QDs) are in an unrivaled position in photoluminescence (PL) performances particularly for green and red color over other heavy‐metal‐free QD visible emitters. ...Herein, based on InP cores synthesized using an easy‐to‐handle, safe aminophosphine precursor, unprecedented bright, narrow emissivity is demonstrated synergically by optimizing double shelling scheme and Ga treatment. Two comparative double shells of ZnSe0.5S0.5/ZnS versus ZnSe/ZnS are generated on green‐emissive InP cores, yielding better PL outcomes with respect to PL quantum yield (QY) and full‐width‐at‐half‐maximum (FWHM) from the latter scheme over the former one. With an intent to further enhance emissivity, incorporation of Ga onto InP cores in the course of ZnSe inner shelling is newly devised. Properly Ga‐treated InP/ZnSe/ZnS QDs, where Ga is presumed to play a beneficial role in removing surface P dangling bond of InP core, produce a near‐unity PLQY (97%) and narrow FWHM of 37 nm. The similar effectiveness is also verified in red InP/ZnSe/ZnS heterostructure, clearly indicating that Ga treatment is a viable, valid strategy toward bright emissivity in the InP QD system.
Based on green‐emissive InP cores synthesized with an aminophosphine precursor, unprecedented bright, narrow emissivity is demonstrated. Double‐shelled quantum dots of InP/ZnSe/ZnS with a photoluminescence quantum yield (QY) of 92% is further subjected to a novel Ga treatment, resulting in a near‐unity QY of 97% due to the proper passivation of surface P dangling bond of InP core.
Considering a strict global environmental regulation, fluorescent quantum dots (QDs) as key visible emitters in the next-generation display field should be compositionally non-Cd. When compared to ...green and red emitters obtainable from size-controlled InP QDs, development of non-Cd blue QDs remains stagnant. Herein, we explore the synthesis of non-Cd, ZnSe-based QDs with binary and ternary compositions toward blue photoluminescence (PL). First, the size increment of binary ZnSe QDs is attempted by a multiply repeated growth until blue PL is attained. Although this approach offers a relevant blue color, excessively large-sized ZnSe QDs inevitably entail a low PL quantum yield. As an alternative strategy to the above size enlargement, the alloying of high-band gap ZnSe with lower-band gap ZnTe in QD synthesis is carried out. These alloyed ternary ZnSeTe QDs after ZnS shelling exhibit a systematically tunable PL of 422–500 nm as a function of Te/Se ratio. Analogous to the state-of-the-art heterostructure of InP QDs with a double-shelling scheme, an inner shell of ZnSe is newly inserted with different thicknesses prior to an outer shell of ZnS, where the effects of the thickness of ZnSe inner shell on PL properties are examined. Double-shelled ZnSeTe/ZnSe/ZnS QDs with an optimal thickness of the ZnSe inner shell are then employed for all-solution-processed fabrication of a blue QD light-emitting diode (QLED). The present blue QLED as the first ZnSeTe QD-based device yields a peak luminance of 1195 cd/m2, a current efficiency of 2.4 cd/A, and an external quantum efficiency of 4.2%, corresponding to the record values reported from non-Cd blue devices.
At a time when the COVID-19 pandemic has been ongoing for more than a year, young people have been the subject of vigilant scrutiny and criticism regarding their active engagement in social ...activities. We posed the question of whether young people's response to COVID-19 was different from that of other generations and analyzed awareness and behavior to investigate this question. Specifically, we examined internet searches for information on COVID-19 and credit card consumption in South Korea among young people in their 20s and compared them to a reference group of people in their 50s. Our research has confirmed that there was no statistically significant difference between young people and the reference group in this regard. Furthermore, in the 25 sub-sectors of industry we examined, young people's consumption activities recovered significantly faster than the reference group in only three sub-sectors. This study demonstrated that young people showed stronger interest than the reference group in their response to COVID-19, and that they cooperated with the government's social distancing policy by reducing their activities. Through this study, we presented a scientific approach for evaluating young people in regard to their response to COVID-19, offering useful implications for designing appropriate policies for public health.
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•Extensive synthesis of deep-blue ZnSeTe QDs with double shells was implemented.•Thicknesses of ZnSe inner and ZnS outer shell were individually modulated.•Te/Se composition of ...blue-emissive ZnSeTe core were finely tuned.•Exceptional EQE of 18.6% was achievable from an optimal QD heterostructure.
Ternary ZnSeTe quantum dots (QDs) are regarded as the most promising non-Cd blue emitters, which can be exploited for the fabrication of self-emissive QD display device or QD-light-emitting diode (QLED). We report extensive synthesis of high-quality blue ZnSeTe QDs with a double shell scheme of ZnSe inner and ZnS outer shell in a unique two-step approach. In such ZnSeTe/ZnSe/ZnS heterostructure, the thickness modulation of ZnSe inner shell leads to the variations in not only the thickness of ZnS outer shell but Photoluminescence (PL) characteristics such as peak wavelength, color purity-associated bandwidth, and Quantum yield (QY). The Te/Se ratio in ZnSeTe core is precisely tailored to demonstrate moderate PL tunability in deep-blue territory and the thickness of ZnS outer shell is further independently varied to examine its effects on the performance of QLED. All the QDs that possess outstanding PL QYs up to near-unity (96%) along with an appropriate deep-blue emissivity are individually employed for solution-processed QLED fabrication. The resulting blue QLEDs produce high electroluminescence performances in the ranges of 6107–12654 cd/m2 in luminance and 5.3–18.6% in external quantum efficiency, depending on ZnSe inner, ZnS outer shell dimensions and ZnSeTe core composition.
Group I–III–VI chalcogenides are emerging candidates for the synthesis of efficient quantum dot (QD) emitters, particularly since they are free from environmentally harmful substances such as Cd, Pb, ...and As. Among them, Cu–In–S (CIS) and Cu–In–Se1–x –S x (CISeS) are the most common compositions as visible and near-infrared (NIR) QD emitters, respectively. We herein explore efficient synthetic pathways to demonstrate extensively emission-tuned CIS QDs from visible to NIR with high photoluminescence quantum yields (PL QYs) of over 70%. To systematically tune PL, synthetic parameters of CIS core QDs are varied such as Cu/In molar ratio, core growth condition, Ag alloying, and In precursor change, whereas a highly reactive elemental sulfur is commonly adopted for core growth. Starting from visible CIS/ZnS QDs, whose emission is tuned in green (534 nm) to red (625 nm), depending on the Cu/In ratio, their emissions gradually shift in the PL peak to 744 nm by controlling the core growth condition to 806 nm by alloying with Ag and further to 868 nm by switching an In salt precursor from In acetate to In iodide. These NIR-emitting QDs, particularly those having PL peaks longer than 800 nm, possess excellent QYs of 81–91%, which are the record values among deep NIR-emitting I–III–VI QDs to date. To enhance the QD stability against environmental stimuli, Al doping into Zn shell is implemented on 868 nm emitting CIS/ZnS QDs, resulting in exceptional photostability under prolonged UV irradiation exposure. These highly luminescent, photostable NIR-emitting CIS/ZnS QDs will be attractive candidates for further application as fluorophores in luminescent solar concentrator and in vivo bioimaging.
Doping particularly with transition metal ions is an effectual means to modulate photoluminescence (PL) of quantum dots (QDs). The precedent doped QDs rely primarily on single doping with either Cu+ ...or Mn2+ into the most common host compositions of (Zn)CdS, ZnSe, and InP, with little success on co‐doping with both impurities enabling their simultaneous emissions. Herein, single and dual doping are explored with Cu+ and/or Mn2+ into blue‐emissive ZnSeTe QDs. PL of the singly doped ZnSeTe QDs synthesized via a co‐nucleation process, comprising host and dopant emissions, is spectrally tuned by varying the concentration of each dopant. For the effective dual doping toward co‐emergence of both dopant‐related emissions, a two‐step doping strategy, where co‐nucleation doping of Mn2+ is temporally decoupled from diffusion doping of Cu+, is devised. In the resulting co‐doped ZnSeTe QDs, successfully showing three distinct emission components, the relative spectral distribution of triple emissions is readily modulated by individually adjusting Cu and Mn concentrations, producing color‐quality tunable white emissions. Upon elaborate multishelling, the co‐doped QDs display outstanding PL quantum yields of 72–75%. Singly and dually doped QDs are further applied for the fabrication of QD light‐emitting diodes, and their electroluminescence is examined compared to PL.
Based on blue‐emissive ZnSeTe quantum dots (QDs), single and dual doping with Cu+ and/or Mn2+ are implemented. Co‐doped ZnSeTe:Mn,Cu QDs synthesized by a two‐step doping route produce well‐resolved triple emission components of blue, green, and orange colors, and their relative spectral intensities are also independently controlled by mutually varying the concentrations of the two dopants.
Last decade witnessed great advancement in the photoluminescent (PL) quality of visible III–V InP quantum dots (QDs) toward bright, sharp emissivity. Now, InP QDs hold an unrivaled position in the ...field of next-generation display devices. In an effort to offer non-Cd green QDs as potential alternatives to InP counterparts, in this work, the first viable synthesis of II–VI ternary ZnSeTe QDs is explored. After successful growth of ZnSeTe alloy cores enabled by a balanced precursor reactivity of anions (i.e., Se and Te), sequential triple shells of ZnSe/ZnSeS/ZnS with stepwise type-I energetic potentials are formed. The resulting heterostructured ZnSeTe/ZnSe/ZnSeS/ZnS QDs produce tunable PL wavelengths of 495–532 nm along with high PL quantum yields (QY) of 68–83%, depending on a Te/Se feed molar ratio used for core synthesis. To further evaluate performance of the present ZnSeTe QDs as electroluminescent (EL) emitters, the first fabrication of a solution-processed, multilayered green QD-light-emitting diode (QLED) by adopting Te/Se = 0.28-based triple-shelled QDs with a PL peak of 520 nm and QY of 80% is demonstrated. This device produces promising EL outcomes up to 18 420 cd/m2 in luminance and 7.6% in external quantum efficiency, outperforming most of green InP QLEDs reported to date.
Indium phosphide (InP) has been regarded as the most promising composition of visible quantum dot (QD) emitters for the application to next-generation display devices primarily because of its ...environmental benignity. Bright, sharp emissivity of InP QDs should be pursued for the realization of high-efficiency, wide-color gamut display devices. Photoluminescence (PL) performance of InP QDs has been greatly improved based on synthetic advances enabling the securement of core size homogeneity and the formation of exquisite core/shell heterostructure. Until now, high-quality fluorescent InP QDs have been attainable exclusively through the use of a hazardous phosphorus (P) precursor of tris(trimethylsilyl)phosphine ((TMS)3P) against green chemistry. In this work, we report a synthetic breakthrough of green InP QDs toward narrow, bright emissivity by using a much cheaper, safer P alternative of tris(dimethylamino)phosphine ((DMA)3P). For this, QD synthesis proceeds via a so-called two-step approach, where as-grown InP cores are subjected to a stepwise size fractionation process and then placed in the consecutive double shelling of a composition-gradient ZnSe x S1–x inner and a ZnS outer shell. The chemical composition (x) of the ZnSe x S1–x inner shell in the range of 0.09–0.36 is varied to explore its effects on PL quantum yield (QY), size, and blue excitation light absorptivity. Because of the effective core size fractionation and elaborately designed heterostructure, the resulting InP/ZnSe x S1–x /ZnS QDs exhibit exceptional green (527 nm) PL features of a sharp line width of 37 nm and a high PL QY of 87%, which have not been achievable to date from non-(TMS)3P-based QDs, when an optimal inner shell composition is applied.
Human norovirus (HuNoV) is the primary cause of viral gastroenteritis worldwide. Fresh blueberries are among high risk foods associated with norovirus related outbreaks. Therefore, it is important to ...assess intervention strategies to reduce the risk of foodborne illness. The disinfection efficiency of decontamination methods is difficult to evaluate for fruits and vegetables due to an inconsistent degree of contamination and irregular surface characteristics. The inactivation efficiency and mechanism of murine norovirus 1 (MNV-1, a surrogate for HuNoV) was studied on an experimentally prepared solidified agar matrix (SAM) to simulate blueberries using different wavelengths (A, B, C) of UV light both with and without TiO2 photocatalysis (TP). MNV-1 was inoculated on exterior and interior of SAM and inactivation efficiencies of different treatments were investigated using a number of assays. Initial inoculum levels of MNV-1 on the SAM surface and interior were 5.2logPFU/mL. UVC with TiO2 (UVC-TP) achieved the highest level of viral reduction for both externally inoculated and internalized MNV-1. Externally inoculated MNV-1 was reduced to non-detectable levels after UVC-TP treatment for 5min while there was still a 0.9 log viral titer after UVC alone. For internalized MNV-1, 3.2 log and 2.7 log reductions were obtained with UVC-TP and UVC alone treatments for 10min, respectively. The Weibull model was applied to describe the inactivation behavior of MNV-1, and the model showed a good fit to the data. An excellent correlation between the steady-state concentration of OH radicals (OHss) and viral inactivation was quantified using a para–chlorobenzoic acid (pCBA) probe compound, suggesting that OH radicals produced in the UV-TP reaction were the major species for MNV-1 inactivation. Transmission electron microscopy images showed that the structure of viral particles was completely disrupted with UVC-TP and UVC alone. SDS-PAGE analysis showed that the major capsid protein VP1 was degraded after UVC-TP and UVC alone. Real-time RT-qPCR analysis showed that UVC-TP and UVC alone caused a reduction in the level of viral genomic RNA. Propidium monoazide (PMA) pretreatment RT-qPCR analysis showed that UVC-TP caused damage to the viral capsid protein in addition to viral genomic RNA. UVC both with and without TiO2 was more effective for MNV-1 inactivation than UVB and UVA. Thus, UVC-TP disinfection aimed to reduce levels of food-borne viruses can inactivate viruses present on the surface and internalized in the interior of blueberries.
•MNV-1 inactivation studied under UV light (A, B, C) both with and without TiO2.•A solidified agar matrix was prepared for simulation of blueberries.•OH radicals were the primary species for TiO2 photocatalytic disinfection of MNV-1.•UVC both with and without TiO2 disrupted capsid protein and genomic RNA of MNV-1.•UVC with TiO2 showed potential for inactivation of external and internalized MNV-1.
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