Suppressing Halide Segregation via Pyridine-Derivative Isomers Enables Efficient 1.68 eV Bandgap Perovskite Solar Cells.

Light-induced phase segregation is one of the main issues restricting the efficiency and stability of wide-bandgap perovskite solar cells (WBG PSCs). Small organic molecules with abundant functional groups can passivate various defects, and therefore suppress the ionic migration channels for phase segregation. Herein, a series of pyridine-derivative isomers containing amino and carboxyl are applied to modify the perovskite surface. The amino, carboxyl, and N-terminal of pyridine in all of these molecules can interact with undercoordinated Pb2+ through coordination bonds and suppress halide ions migration via hydrogen bonding. Among them, the 5-amino-3-pyridine carboxyl acid (APA-3) treated devices win the champion performance, enabling an efficiency of 22.35% (certified 22.17%) using the 1.68 eV perovskite, which represents one of the highest values for WBG-PSCs. This is believed to be due to the more symmetric spatial distribution of the three functional groups of APA-3, which provides a better passivation effect independent of the molecular arrangement orientation. Therefore, the APA-3 passivated perovskite shows the slightest halide segregation, the lowest defect density, and the least nonradiative recombination. Moreover, the APA-3 passivated device retains 90% of the initial efficiency after 985 h of operation at the maximum power point, representing the robust durability of WBG-PSCs under working conditions.

Efficient Semi-Transparent Wide-Bandgap Perovskite Solar Cells Enabled by Pure-Chloride 2D-Perovskite Passivation.

Wide-bandgap (WBG) perovskite solar cells suffer from severe non-radiative recombination and exhibit relatively large open-circuit voltage (VOC) deficits, limiting their photovoltaic performance. Here, we address these issues by in-situ forming a well-defined 2D perovskite (PMA)2PbCl4 (phenmethylammonium is referred to as PMA) passivation layer on top of the WBG active layer. The 2D layer with highly pure dimensionality and halide components is realized by intentionally tailoring the side-chain substituent at the aryl ring of the post-treatment reagent. First-principle calculation and single-crystal X-ray diffraction results reveal that weak intermolecular interactions between bulky PMA cations and relatively low cation-halide hydrogen bonding strength are crucial in forming the well-defined 2D phase. The (PMA)2PbCl4 forms improved type-I energy level alignment with the WBG perovskite, reducing the electron recombination at the perovskite/hole-transport-layer interface. Applying this strategy in fabricating semi-transparent WBG perovskite solar cells (indium tin oxide as the back electrode), the VOC deficits can be reduced to 0.49 V, comparable with the reported state-of-the-art WBG perovskite solar cells using metal electrodes. Consequently, we obtain hysteresis-free 18.60%-efficient WBG perovskite solar cells with a high VOC of 1.23 V.

Automated screening of COVID-19 using two-dimensional variational mode decomposition and locally linear embedding.

In order to aid imaging physicians to effectively screen chest radiography medical images for presence of Coronavirus Disease 2019 (COVID-19), a novel computer aided diagnosis technology for automatic processing of COVID-19 images is proposed based on two-dimensional variational mode decomposition (2D-VMD) and locally linear embedding (LLE). 2D-VMD algorithm is used to decompose normal and COVID-19 images, and then feature extraction of intrinsic mode functions (IMFs) using Gabor filter. To better extract low-dimensional parameters which are useful for COVID-19 diagnosis, the performance of two dimensionality reduction techniques of principal component analysis (PCA) and LLE are compared, and the LLE is shown to offer satisfactory effect of dimension reduction. Thereafter, the particle swarm optimization-support vector machine (PSO-SVM) algorithm is used to classify. The simulation results show that the proposed technology has achieved accuracy of 99.33%, precision of 100%, recall of 98.63% and F-Measure of 99.31%. Hence, the developed diagnosis technology can be used as an important auxiliary tool to assist diagnosis of imaging physicians.

Comparison of Vibration-Assisted Scratch Characteristics of SiC Polytypes (3C-, 4H- and 6H-SiC).

Single-crystal silicon carbide (SiC) is widely used because of its excellent properties. However, SiC is a typical hard and brittle material, and there are many challenges in realizing its high efficiency and high-precision machining. Grinding is the main method used to achieve the high-efficiency processing of SiC, but the contradiction between processing quality and processing efficiency is prominent. Vibration-assisted grinding is an effective method to realize high-efficiency and precision machining of SiC. To reveal the vibration-assisted grinding mechanism of SiC, the vibration-assisted nano-scratch process is studied using the molecular dynamics method, and the material removal process and damage formation mechanism in the vibration-assisted scratch are analyzed. Aiming at the three main structural crystal types, 3C-, 4H- and 6H-SiC, scratch simulations were carried out. The vibration-assisted scratch characteristics of SiC polytypes were evaluated from the perspectives of scratch force and the amorphous layer. It was found that the effects of vibration-assisted scratch on different crystal structures of SiC differ, and 3C-SiC is quite different from 4H- and 6H-SiC. Through vibration-assisted scratch simulations under different scratch conditions and vibration characteristics, the influence laws for machining parameters and vibration characteristic parameters were explored. It was found that increasing the frequency and amplitude was beneficial for improving the machining effect. This provides a basis for vibration-assisted grinding technology to be used in the high-efficiency precision machining of SiC.

Ablation characteristics and material removal mechanisms of a single-crystal diamond processed by nanosecond or picosecond lasers.

The microstructures on a diamond surface have attracted extensive attention in microelectronics, ultra-precision machining tools, and optical elements, etc. In this work, microgrooves were fabricated on a single-crystal diamond surface using ultraviolet nanosecond or infrared picosecond laser pulses. The surface and internal morphologies of the microgrooves were characterized. The chemical composition and phase transition of the diamond after laser irradiation were analyzed. Furthermore, the ablation threshold, ablation rate, and material removal rate of the diamond processed by nanosecond or picosecond lasers were also calculated. In addition, the temperature distributions of the diamond ablated by nanosecond or picosecond lasers were simulated. Finally, the material removal mechanisms of a single-crystal diamond processed by nanosecond or picosecond lasers were revealed. This work is expected helpful to provide a guidance for the laser fabrication of microstructures on diamond.

Focused Ion Beam Milling of Single-Crystal Sapphire with A-, C-, and M-Orientations.

Sapphire substrates with different crystal orientations are widely used in optoelectronic applications. In this work, focused ion beam (FIB) milling of single-crystal sapphire with A-, C-, and M-orientations was performed. The material removal rate (MRR) and surface roughness (Sa) of sapphire with the three crystal orientations after FIB etching were derived. The experimental results show that: The MRR of A-plane sapphire is slightly higher than that of C-plane and M-plane sapphires; the Sa of A-plane sapphire after FIB treatment is the smallest among the three different crystal orientations. These results imply that A-plane sapphire allows easier material removal during FIB milling compared with C-plane and M-plane sapphires. Moreover, the surface quality of A-plane sapphire after FIB milling is better than that of C-plane and M-plane sapphires. The theoretical calculation results show that the removal energy of aluminum ions and oxygen ions per square nanometer on the outermost surface of A-plane sapphire is the smallest. This also implies that material is more easily removed from the surface of A-plane sapphire than the surface of C-plane and M-plane sapphires by FIB milling. In addition, it is also found that higher MRR leads to lower Sa and better surface quality of sapphire for FIB etching.

Piezo1 activates the NLRP3 inflammasome in nucleus pulposus cell-mediated by Ca2+/NF-κB pathway.

Studying and understanding the mechanism of inflammation in nucleus pulposus is the key to understand and prevent intervertebral disc degeneration. We propose a model of mechanical sensitive ion channel Piezo1 mediated inflammation of nucleus pulposus cells. Piezo1 can up-regulate the level of interleukin-1ß (IL-1ß) in nucleus pulposus cells once it is activated. It is suggested that Piezo1 may mediate inflammation by activating Nod-like receptor protein 3 (NLRP3) inflammasome to accelerate the production and maturation of IL-1ß. The primary objective of this study was to explore whether Piezo1 activates NLRP3 inflammasome in nucleus pulposus cells. Piezo1 sensitization was induced by mechanical stretch following which we analyzed the priming and assembly of NLRP3 inflammasome and also studied if the downstream Ca2+/NF-κB pathway mediated this activation in nucleus pulposus cells. The expression of Piezo1 and NLRP3 inflammasome increased in a time-dependent manner upon mechanical stretch. Piezo1 activation promoted NLRP3 inflammasome assembly, which was demonstrated by the upregulation of caspase-1 activation and IL-1ß production. Transfection of Piezo1-siRNA reversed this process. The inhibition of Ca2+/NF-κB pathway reduced Piezo1-dependent activation of NLRP3 inflammasome. Thus, we propose that activation of NLRP3 inflammasome in nucleus pulposus cells mediated by Piezo1 through the Ca2+/NF-κB pathway is a novel pathogenesis for the progress of intervertebral disc degeneration. As per our knowledge this is the first study which has provided evidence linking Piezo1-mediated inflammation in nucleus pulposus cells with the production of NLRP3 inflammasome.

Model-free determination of the birefringence and dichroism in c-cut crystals from transmission ellipsometry measurements.

In this work, we derive closed-form expressions for determination of the linear birefringence and linear dichroism of uniaxial crystals utilizing transmission ellipsometry measurements at small angles of incidence in $ c $c-cut crystal substrates. The model-free method we use is an algebraic generalization of the method reported in Appl. Opt.44, 3153 (2005).APOPAI0003-693510.1364/AO.44.003153 The optical anisotropy of substrates of sapphire, 4H-SiC, and 6H-SiC single crystals is measured for illustration.

Proactive crash risk prediction modeling for merging assistance system at interchange merging areas.

Objective: Ramp drivers have to merge into the through traffic in a limited time and space at interchange merging areas. Different merging decisions are made due to drivers' various perception abilities of potential danger, which might significantly increase the crash risk. Driving assistance technology (DA) is expected to be an effective way of mitigating the crash risk. Hence, this paper aims to contribute to the literature by designing a model strategy to predict the crash risk of merging drivers in order to enhance the merging assistance system for crash avoidance.Methods: Unmanned aerial vehicle (UAV) was used to collect individual vehicle data to conduct traffic analysis at the microscopic level. A model strategy was proposed to predict the crash risk of merging vehicles which could make sure that ramp drivers are aware of potential risks in advance. Three models (i.e., binary logistic regression, multinomial logistic regression, and nested logit models) were developed and compared.Results: Target-lane-related and merging-vehicle-related variables were found significant with crash risk, including the speed of the merging vehicle, the speed of lead/lag vehicle in the target lane, the type of lead/lag vehicle in the target lane. Different variables were found to be significant in the proposed models.Conclusions: The results suggest that the nested logit model has the highest prediction accuracy. It is concluded that the merging speed, driving ability (i.e., lane-keeping instability), and the vehicle type in the target lane affect the crash risk. Finally, the implementation of the proposed prediction model for merging assistance system is designed. The findings from this study can have implications for the design of the merging assistance system for helping drivers make safe merging decisions and thus enhancing the safety of the interchange merging area.

Model Establishment of a Co-Based Metal Matrix with Additives of WC and Ni by Discrete Element Method.

A metal matrix is an indispensable component of metal-bonded diamond tools. The composition design of a metal matrix involves a number of experiments, making costly in terms of time, labor, and expense. The discrete element method (DEM) is a potential way to relieve these costs. The aim of this work is to demonstrate a methodology for establishing and calibrating metal matrix's DEM model. A Co-based metal matrix with WC and Ni additives (CoX⁻WC⁻Ni) was used, in which the Co-based metal was Co⁻Cu⁻Sn metal (CoX). The skeletal substances in the metal matrix were treated as particles in the model, and the bonding substances were represented by the parallel bond between particles. To describe the elasticity of the metal matrix, a contact bond was also loaded between particles. A step-by-step calibration procedure with experimental tests of three-point bending and compression was proposed to calibrate all microcosmic parameters involved during the establishment of DEM models: first for the CoX matrix, then for the CoX⁻WC matrix and CoX⁻Ni matrix, and finally for the CoX⁻WC⁻Ni matrix. The CoX⁻WC⁻Ni DEM model was validated by the transverse rupture strength (TRS) of two new compositions and the results indicated that the model exhibited a satisfactory prediction ability with an error rate of less than 10%.

Percent Reduction in Transverse Rupture Strength of Metal Matrix Diamond Segments Analysed via Discrete-Element Simulations.

The percent TRS reduction, DTRS, which is the percent reduction of the transverse rupture strength of metal matrix diamond segments with or without diamonds, is a key metric for evaluating the bonding condition of diamonds in a matrix. In this work, we build, calibrate, and verify a discrete-element simulation of a metal matrix diamond segment to obtain DTRS for diamond segments with various diamond-grain sizes, concentrations, and distributions. The results indicate that DTRS increases with increasing diamond-grain concentration and decreases with increasing diamond-grain size. Both factors can be explained by the total diamond contact length, the increase of which causes the increase in DTRS. The distribution of diamond grains in segments also strongly influences the increase of DTRS. The use of DTRS as a metric to assess the bonding condition of diamonds in matrixes is not valid unless the diamond-grain size, concentration, and distribution and total diamond contact length are the same for all diamond segments under consideration.

FEM Modeling of the Relationship between the High-Temperature Hardness and High-Temperature, Quasi-Static Compression Experiment.

The high-temperature hardness test has a wide range of applications, but lacks test standards. The purpose of this study is to develop a finite element method (FEM) model of the relationship between the high-temperature hardness and high-temperature, quasi-static compression experiment, which is a mature test technology with test standards. A high-temperature, quasi-static compression test and a high-temperature hardness test were carried out. The relationship between the high-temperature, quasi-static compression test results and the high-temperature hardness test results was built by the development of a high-temperature indentation finite element (FE) simulation. The simulated and experimental results of high-temperature hardness have been compared, verifying the accuracy of the high-temperature indentation FE simulation.The simulated results show that the high temperature hardness basically does not change with the change of load when the pile-up of material during indentation is ignored. The simulated and experimental results show that the decrease in hardness and thermal softening are consistent. The strain and stress of indentation were analyzed from the simulated contour. It was found that the strain increases with the increase of the test temperature, and the stress decreases with the increase of the test temperature.

The Synthesis of the Core/Shell Structured Diamond/Akageneite Hybrid Particles with Enhanced Polishing Performance.

In this study, the synthesis of the core/shell structured diamond/akageneite hybrid particles was performed through one-step isothermal hydrolyzing. The hybrid particle was characterized by X-ray diffraction, field emission scanning electron microscopy, and Fourier transform infrared spectra. The test results overall reveal that the akageneite coating, phase ß-FeO(OH), was uniformly coated onto the diamond surface. The polishing performance of the pristine diamond and hybrid particles for the sapphire substrate was evaluated respectively. The experimental results show that the hybrid particles exhibited improved polishing quality and prolonged effective processing time of polishing pad compared with diamond particles without compromising the material remove rate and surface roughness. The improved polishing behavior might be attributed to the ß-FeOOH coating, which is conducive to less abrasive shedding and reducing the scratch depth.

Intraoperative neurophysiological monitoring to protect the facial nerve during microsurgery for large vestibular schwannomas.

OBJECTIVE: Microsurgery is the preferred treatment for large vestibular schwannomas (VSs). However, anatomical and functional preservation of the facial nerve (FN) remains a challenge during this surgery. The aim of this study was to determine whether it is beneficial to the preservation rates of the FN during microsurgical treatment of large VSs using intraoperative neurophysiological monitoring (IONM). METHODS: We retrospectively reviewed 53 patients with large VSs that underwent microsurgical resection via the retrosigmoid approach in our department during April 2009 to March 2016. IONM was used in 29 cases. Postoperative FN function was evaluated using the House-Brankmann (HB) FN grading scale at 2 weeks and 3 and 6 months after surgery. RESULTS: There were two cases (8.3%) of subtotal resection in the monitored group, compared with one case (3.4%) among the controls (p>0.05). The anatomical integrity rate for FNs was 100% in the monitored group, which was significantly different from 83.3% in the controls (p<0.05), which included four cases the FN was injured, mostly around the internal auditory foramen. Functional preservation of the FN in the monitored group differed significantly from that in the controls at 2 weeks and 3 and 6 months postoperatively (p<0.05). CONCLUSIONS: IONM contributes to FN anatomical integrity and functional preservation rates during microsurgery of large VSs. It has no significant effect on differences in the total VS resection rates.

Preparation and Characterization of Zirconia-Coated Nanodiamonds as a Pt Catalyst Support for Methanol Electro-Oxidation.

Zirconia-coated nanodiamond (ZrO2/ND) electrode material was successfully prepared by one-step isothermal hydrolyzing from ND-dispersed ZrOCl2·8H2O aqueous solution. High-resolution transmission electron microscopy reveals that a highly conformal and uniform ZrO2 shell was deposited on NDs by this simple method. The coating obtained at 90 °C without further calcination was mainly composed of monoclinic nanocrystalline ZrO2 rather than common amorphous Zr(OH)4 clusters. The ZrO2/NDs and pristine ND powder were decorated with platinum (Pt) nanoparticles by electrodeposition from 5 mM chloroplatinic acid solution. The electrochemical studies indicate that Pt/ZrO2/ND catalysts have higher electrocatalytic activity and better stability for methanol oxidation than Pt/ND catalysts in acid.

Inhibiting the oxidation of diamond during preparing the vitrified dental grinding tools by depositing a ZnO coating using direct urea precipitation method.

Oxidation of diamond during the manufacturing of vitrified dental grinding tools would reduce the strength and sharpness of tools. Zinc oxide (ZnO) coating was deposited on diamond particles by urea precipitation method to protect diamond in borosilicate glass. The FESEM results showed that the ZnO coating was formed by plate-shaped particles. According to the TG results, the onset oxidation temperature of the ZnO-coated diamond was about 70 °C higher than the pristine diamond. The EDS results showed that ZnO diffused into the borosilicate glass during sintering. As the result, the bending strength of the composites containing ZnO-coated diamond was increased by 24% compared to that of the composites containing pristine diamond.