Interpretable Ensemble Learning for Materials Property Prediction with Classical Interatomic Potentials: Carbon as an Example

Machine learning (ML) is widely used to explore crystal materials and predict their properties. However, the training is time-consuming for deep-learning models, and the regression process is a black box that is hard to interpret. Also, the preprocess to transfer a crystal structure into the input of ML, called descriptor, needs to be designed carefully. To efficiently predict important properties of materials, we propose an approach based on ensemble learning consisting of regression trees to predict formation energy and elastic constants based on small-size datasets of carbon allotropes as an example. Without using any descriptor, the inputs are the properties calculated by molecular dynamics with 9 different classical interatomic potentials. Overall, the results from ensemble learning are more accurate than those from classical interatomic potentials, and ensemble learning can capture the relatively accurate properties from the 9 classical potentials as criteria for predicting the final properties

Direct pulsed laser crystallization of nanocrystals for absorbent layers in photovoltaics: Multiphysics simulation and experiment

Direct pulsed laser crystallization (DPLC) of nanoparticles of photoactive material-Copper Indium Selenide (nanoCIS) is investigated by multiphysics simulation and experiments. Laser interaction with nanoparticles is fundamentally different from their bulk counterparts. A multiphysics electromagnetic-heat transfer model is built to simulate DPLC of nanoparticles. It is found smaller photoactive nanomaterials (e.g., nanoCIS) require less laser fluence to accomplish the DPLC due to their stronger interactions with incident laser and lower melting point. The simulated optimal laser fluence is validated by experiments observation of ideal microstructure. Selectivity of DPLC process is also confirmed by multiphysics simulation and experiments. The combination effects of pulse numbers and laser intensity to trigger laser ablation are investigated in order to avoid undesired results during multiple laser processing. The number of pulse numbers is inversely proportional to the laser fluence to trigger laser ablation. (C) 2013 AIP Publishing LLC

Ultraviolet laser crystallized ZnO:Al films on sapphire with high Hall mobility for simultaneous enhancement of conductivity and transparency

One of the most challenging issues in transparent conductive oxides (TCOs) is to improve their conductivity without compromising transparency. High conductivity in TCO films often comes from a high carrier concentration, which is detrimental to transparency due to free carrier absorption. Here we show that UV laser crystallization (UVLC) of aluminum-doped ZnO (AZO) films prepared by pulsed laser deposition on sapphire results in much higher Hall mobility, allowing relaxation of the constraints of the conductivity/transparency trade-off. X-ray diffraction patterns and morphological characterizations show grain growth and crystallinity enhancement during UVLC, resulting in less film internal imperfections. Optoelectronic measurements show that UVLC dramatically improves the electron mobility, while the carrier concentration decreases which in turn simultaneously increases conductivity and transparency. AZO films under optimized UVLC achieve the highest electron mobility of 79 cm(2)/V s at a low carrier concentration of 7.9 x 10(+19) cm(-3). This is realized by a laser crystallization induced decrease of both grain boundary density and electron trap density at grain boundaries. The infrared (IR) to mid-IR range transmittance spectrum shows UVLC significantly enhances the AZO film transparency without compromising conductivity. (C) 2014 AIP Publishing LLC

Molecular-Scale Nanodiamond with High-Density Color Centers Fabricated from Graphite by Laser Shocking

Nanodiamonds (NDs) with nitrogen vacancy (NV) color centers have the potential for quantum information science and bioimaging due to their stable and non-classical photon emission at room temperature. Large-scale fabrication of molecular-size nanodiamonds with sufficient color centers may economically promote their application in versatile multidisciplinary fields. Here, the manufacture of molecular-size NV center-enriched nanodiamonds from graphite powder is reported. We use an ultrafast laser shocking technique to generate intense plasma, which transforms graphite to nanodiamonds under the confinement layer. Molecular dynamics simulations suggest that the high pressure of 35 GPa and the high temperature of 3,000K result in the metaphase transition of graphite to nanodiamonds within 100 ps. A high concentration of NV centers is observed at the optimal laser energy of 3.82 GW/cm2, at which point molecular-size (∼5 nm) nanodiamonds can individually host as many as 100 NV centers. Consecutive melamine annealing following ultrafast laser shocking enriches the number of NV centers >10-fold and enhances the spontaneous decay rate of the NV center by up to 5 times. Our work may enhance the feasibility of nanodiamonds for applications, including quantum information, electromagnetic sensing, bioimaging, and drug delivery

3D Printing‐Enabled Design and Manufacturing Strategies for Batteries: A Review

Lithium-ion batteries (LIBs) have significantly impacted the daily lives, finding broad applications in various industries such as consumer electronics, electric vehicles, medical devices, aerospace, and power tools. However, they still face issues (i.e., safety due to dendrite propagation, manufacturing cost, random porosities, and basic & planar geometries) that hinder their widespread applications as the demand for LIBs rapidly increases in all sectors due to their high energy and power density values compared to other batteries. Additive manufacturing (AM) is a promising technique for creating precise and programmable structures in energy storage devices. This review first summarizes light, filament, powder, and jetting-based 3D printing methods with the status on current trends and limitations for each AM technology. The paper also delves into 3D printing-enabled electrodes (both anodes and cathodes) and solid-state electrolytes for LIBs, emphasizing the current state-of-the-art materials, manufacturing methods, and properties/performance. Additionally, the current challenges in the AM for electrochemical energy storage (EES) applications, including limited materials, low processing precision, codesign/comanufacturing concepts for complete battery printing, machine learning (ML)/artificial intelligence (AI) for processing optimization and data analysis, environmental risks, and the potential of 4D printing in advanced battery applications, are also presented

Pharmacokinetics of Acetaminophen and Metformin Hydrochloride in Rats After Exposure to Simulated High Altitude Hypoxia

The pharmacokinetic characteristics of drugs were altered under high altitude hypoxia, thereby affecting the absorption, distribution, metabolism, and excretion of drug. However, there are few literatures on the pharmacokinetic changes of antipyretic and pain-relieving drugs and cardiovascular system drugs at high altitude. This study aimed to evaluate the pharmacokinetics of acetaminophen and metformin hydrochloride in rats under simulated high altitude hypoxia condition. Mechanically, the protein and mRNA expression of uridine diphosphate glucuronyltransferase 1A1 (UGT1A1) and organic cation transporter 2 (OCT2) were investigated by enzyme linked immunosorbent assay (ELISA) and quantitative real-time polymerase chain reaction (qRT-PCR), respectively. Compared with the normoxia group, the t1/2 and AUC of acetaminophen were significantly increased, and the CL/F was significantly decreased in rats after exposure to simulated high altitude hypoxia. The t1/2 of metformin hydrochloride was significantly increased by simulated high altitude hypoxia. No significant differences in AUC and CL/F of metformin hydrochloride were observed when comparing the hypoxia group with the normoxia group. The protein and mRNA expression of UGT1A1 and OCT2 were decreased significantly under hypoxia in rats. This study found obvious changes in the pharmacokinetics of acetaminophen and metformin hydrochloride in rats after exposure to simulated high altitude hypoxia, and they might be due to significant decreases in the expressions of UGT1A1 and OCT2. To sum up, our data suggested that the pharmacokinetics of acetaminophen and metformin hydrochloride should be reexamined, and the optimal dose should be reassessed under hypoxia exposure

Ultra-fast laser enhanced printing of nanomaterial for high quality transparent electrode

Direct printing of nanomaterials, which integrate nanomaterials into a film via low cost mean, is designed to fabricate transparent conductive electrode (TCE) film. Following laser processing is utilized as the post treatment to enhance the film performance. The laser processing is proposed in order to weld nanomaterials in nanoscale and enhance the electrical conductance of the nanomaterials film after direct printing. Rigid glass substrate was chosen as the substrate to load nanomaterials printing; however, this laser processing also can be utilized to nanomaterials printed on flexible substrate like polymer and bendable glass. Aluminum doped zinc oxide nanoparticles and silver nanowires were chosen as the printable nanomaterials. The laser – nanomaterial interaction and temperature evolution was studied by Comsol Multiphysics software. The nature intrinsic of laser induced localized nanowelding was simulated by Molecular Dynamic simulation. The SEM, TEM and XRD results show that microstructure of nanomaterials film was improved significantly after laser induced nanowelding. The performance evaluation confirms the improved optoelectronic property of nanomaterials printing film. The theoretical study of the electrical conductance enhancement is presented in the thesis. The direct printing techniques and ultra-fast laser processing have the potential to boost the efficiency when used in commercial mass – production

Room temperature deposition of alumina-doped zinc oxide on flexible substrates by direct pulsed laser recrystallization

In this study, a method combining room temperature pulsed laser deposition (PLD) and direct pulsed laser recrystallization (DPLR) is introduced to deposit transparent conductive oxide (TCO) layer on low melting point flexible substrates. Alumina-doped zinc oxide (AZO), as one of the most promising TCO candidates, has now been widely used in solar cells. However, to achieve optimal, electrical, and optical properties of AZO on low melting point, flexible substrate is challenging. DPLR technique is a scalable, economic, and fast process to remove crystal defects and generate recrystallization at room temperature. It features selective processing by only heating up the TCO thin film and preserve the underlying substrate at low temperature. In this study, AZO thin film is pre-deposited by PLD on flexible and rigid substrates. DPLR is then introduced to achieve a uniform TCO layer on these substrates, i.e., commercialized Kapton polyimide film, micron-thick Al-foil, and sold lime glass (SLG). Both finite element analysis simulation and designed experiments are carried out to demonstrate that DPLR is promising in manufacturing high quality AZO layers without any damage to the underlying flexible substrates. The hall mobility of AZO after DPLR on Kapton and SLG reached 198 cm(2)/v . s and 398 cm(2)/v . s respectively, while the carrier concentrations are reduced to 2.68 x 10(18) and 4.3 x 10(19) /cm(-2), respectively. These characteristics are exactly what an ideal TCO layer should carry: high conductivity and high transmission. The property changes are due to the reduction of defect density after DPLR. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3702460

Highly Transparent Conductive Electrode with Ultra-Low HAZE by Grain Boundary Modification of Aqueous Solution Fabricated Alumina-Doped Zinc Oxide Nanocrystals

Commercial production of transparent conducting oxide (TCO) polycrystalline films requires high electrical conductivity with minimal degradation in optical transparency. Aqueous solution deposited TCO films would reduce production costs of TCO films but suffer from low electrical mobility, which severely degrades both electrical conductivity and optical transparency in the visible spectrum. Here, we demonstrated that grain boundary modification by ultra-violet laser crystallization (UVLC) of solution deposited aluminium-doped zinc oxide (AZO) nanocrystals results in high Hall mobility, with a corresponding dramatic improvement in AZO electrical conductance. The AZO films after laser irradiation exhibit electrical mobility up to 18.1 cm2 V−1 s−1 with corresponding electrical resistivity and sheet resistances as low as 1 × 10−3 Ω cm and 75 Ω/sq, respectively. The high mobility also enabled a high transmittance (T) of 88%-96% at 550 nm for the UVLC films. In addition, HAZE measurement shows AZO film scattering transmittance as low as 1.8%, which is superior over most other solution deposited transparent electrode alternatives such as silver nanowires. Thus, AZO films produced by the UVLC technique have a combined figure of merit for electrical conductivity, optical transparency, and optical HAZE higher than other solution based deposition techniques and comparable to vacuumed based deposition methods

Confidence intervals construction for difference of two means with incomplete correlated data

Abstract Background Incomplete data often arise in various clinical trials such as crossover trials, equivalence trials, and pre and post-test comparative studies. Various methods have been developed to construct confidence interval (CI) of risk difference or risk ratio for incomplete paired binary data. But, there is little works done on incomplete continuous correlated data. To this end, this manuscript aims to develop several approaches to construct CI of the difference of two means for incomplete continuous correlated data. Methods Large sample method, hybrid method, simple Bootstrap-resampling method based on the maximum likelihood estimates (B 1) and Ekbohm’s unbiased estimator (B 2), and percentile Bootstrap-resampling method based on the maximum likelihood estimates (B 3) and Ekbohm’s unbiased estimator (B 4) are presented to construct CI of the difference of two means for incomplete continuous correlated data. Simulation studies are conducted to evaluate the performance of the proposed CIs in terms of empirical coverage probability, expected interval width, and mesial and distal non-coverage probabilities. Results Empirical results show that the Bootstrap-resampling-based CIs B 1, B 2, B 4 behave satisfactorily for small to moderate sample sizes in the sense that their coverage probabilities could be well controlled around the pre-specified nominal confidence level and the ratio of their mesial non-coverage probabilities to the non-coverage probabilities could be well controlled in the interval [0.4, 0.6]. Conclusions If one would like a CI with the shortest interval width, the Bootstrap-resampling-based CIs B 1 is the optimal choice