Surface Tension of GaInSnBiZn Liquid High-entropy Alloy

As an emerging alloy material, high-entropy alloy has potential applications that distinguish it from traditional alloys due to its special physicochemical properties. In this work, a low melting point GaInSnBiZn high-entropy alloy was designed based on Miedema model, and its surface tension was measured by the continuous pendant-drop method. The results show that the intrinsic surface tension of GaInSnBiZn high-entropy alloy at 80 °C is 545±5 mN/m, and the surface tension of the liquid alloy is significantly reduced by the formation of surface oxide film. The surface tension of GaInSnBiZn high-entropy alloy was analyzed by using theoretical models (Guggenheim model, GSM (general solution) model and Butler model), and the thermodynamic characteristics of the surface tension formation were further verified by combining with thermodynamic calculations, among which the calculated results of Butler model were in good agreement with the experimental data. Meanwhile, it is found that the surface concentration of Bi in the alloy is much larger than the nominal concentration of its bulk phase, which contributes the most to the surface tension of the alloy, however, it contributes the least to the entropy of the alloy formation in combination with the Butler model

An Experimental Test of the Effectiveness of Customized Narrative and Non-Narrative Health Blogs

This dissertation examined the persuasive effects of narratives and customization in a health blog on readers' attitudes, self-efficacy, subjective norms, and intention to adopt a health behavior (running for exercise). Narratives are stories with a beginning, middle, and end that provide information about the characters and plot. Customization refers to matching messages to each individual recipient. Narratives and customization have seldom been examined in tandem as strategies for effective health communication. In this dissertation, the message type (narrative vs. non-narrative) and the customization type between the blogger and each reader (no customization, health behavior-unrelated customization, and health behavior-related customization) were manipulated in a between-subjects pre-post experimental design. Findings suggest that narratives and customization can be powerful health communication tools if applied appropriately. Readers of the narrative health messages intended to engage in longer periods of running than those who read non-narrative messages. Narrative messages also outperformed non-narrative messages when the health messages were not customized, or were customized with similarities unrelated to running (e.g., both the blogger and the reader liked the color green). Bloggers who shared health-related characteristics with the reader elicited stronger intentions to run and to run for longer each time than bloggers who were similar but only on characteristics unrelated to running. The study also showed that narrative and non-narrative messages were processed differently. Customization increased effortful processing (as measured by the number of thought meaning units), but only for non-narrative messages. Narrative messages tended to elicit more positive thoughts than the non-narrative messages

Global gross primary productivity and water use efficiency changes under drought stress

Drought can affect the structure, composition and function of terrestrial ecosystems, yet drought impacts and post-drought recovery potentials of different land cover types have not been extensively studied at a global scale. We evaluated drought impacts on gross primary productivity (GPP), evapotranspiration (ET), and water use efficiency (WUE) of different global terrestrial ecosystems, as well as the drought-resilience of each ecosystem type during the period of 2000 to 2011. Using GPP as biome vitality indicator against drought stress, we developed a model to examine ecosystem resilience represented by the length of recovery days (LRD). LRD presented an evident gradient of high (\u3e60 days) in mid-latitude region and low (\u3c60 days) in low (tropical area) and high (boreal area) latitude regions. As average GPP increased, the LRD showed a significantly decreasing trend, indicating readiness to recover after drought, across various land cover types (R 2 = 0.68, p \u3c 0.0001). Moreover, zonal analysis revealed that the most dramatic reduction of the drought-induced GPP was found in the mid-latitude region of the Northern Hemisphere (48% reduction), followed by the low-latitude region of the Southern Hemisphere (13% reduction). In contrast, a slightly enhanced GPP (10%) was evident in the tropical region under drought impact. Additionally, the highest drought-induced reduction of ET was found in the Mediterranean area, followed by Africa. Water use efficiency, however, showed a pattern of decreasing in the Northern Hemisphere and increasing in the Southern Hemisphere. Drought induced reductions of WUE ranged from 0.96% to 27.67% in most of the land cover types, while the increases of WUE found in Evergreen Broadleaf Forest and savanna were about 7.09% and 9.88%, respectively. These increases of GPP and WUE detected during drought periods could either be due to water-stress induced responses or data uncertainties, which require further investigation

Research on shearer positioning experiment based on IMU and UWB at the end of underground coal mining working face

The long-term precision of shearer independent positioning device is an important research content of intelligent mining. The current shearer positioning accuracy is hard to meet the demands of automatic mining, and we established a fusion positioning model based on IMU/UWB, and proposed autonomous correction to compensate the drift error of inertial navigation device for the coal mine working face by using the fusion results of IMU/UWB to correct the position and posture of inertial positioning system. It can compensate the deviation of IMU in real time, and realize long-term high-precision autonomous cycle cutting of the shearer. To reduce the influence of uncertain measurement noise on the positioning results, we use variational Bayesian unscented Kalman filter (VB-UKF) technique to smooth the positioning results in order to further improve the fusion positioning accuracy. To verify the positioning accuracy of the mining face end, fusion positioning experiments are conducted in Taiyuan Heavy Machinery Co., Ltd on the ground and Shandong Energy Group coal mine working face in the underground, respectively. The experimental results demonstrate that, the accuracy of IMU/UWB fusion positioning is higher than that of the single UWB solution. After smoothing via the VB-UKF algorithm, the error in the x-axis and z-axis orientation of the IMU/UWB fusion localization for underground experiments decreased from 0.0102 m and 0.194 m to 0.082 m and 0.158 m, respectively, and the corresponding average accuracy improved by 19.6% and 18.6%. The error of the three pose angles is less than 2°, because the error extended Kalman filter compensates and modifies the IMU bias in the fusion localization model, which can effectively suppress the drift of the IMU posture angle. The underground field experiment proves the effectiveness of the positioning method of coal mining face end, which provides better reference and experience for the further application in underground coalmine by using IMU/UWB fusion positioning

Comparison Study of Wide Bandgap Polymer (PBDB-T) and Narrow Bandgap Polymer (PBDTTT-EFT) as Donor for Perylene Diimide Based Polymer Solar Cells

Perylene diimide (PDI) derivatives as a kind of promising non-fullerene-based acceptor (NFA) have got rapid development. However, most of the relevant developmental work has focused on synthesizing novel PDI-based structures, and few paid attentions to the selection of the polymer donor in PDI-based solar cells. Wide bandgap polymer (PBDB-T) and narrow bandgap polymer (PBDTTT-EFT) are known as the most efficient polymer donors in polymer solar cells (PSCs). While PBDB-T is in favor with non-fullerene acceptors achieving power conversion efficiency (PCE) more than 12%, PBDTTT-EFT is one of the best electron donors with fullerene acceptors with PCE up to 10%. Despite the different absorption profiles, the working principle of these benchmark polymer donors with a same electron acceptor, specially PDI-based acceptors, was rarely compared. To this end, we used PBDB-T and PBDTTT-EFT as the electron donors, and 1,1′-bis(2-methoxyethoxyl)-7,7′-(2,5-thienyl) bis-PDI (Bis-PDI-T-EG) as the electron acceptor to fabricate PSCs, and systematically compared their differences in device performance, carrier mobility, recombination mechanism, and film morphology

15.34% efficiency all-small-molecule organic solar cells with an improved fill factor enabled by a fullerene additive

Solution processed organic solar cells (OSCs) composed of all small molecules (ASM) are promising for production on an industrial scale owing to the properties of small molecules, such as well-defined chemical structures, high purity of materials, and outstanding repeatability from batch to batch synthesis. Remarkably, ASM OSCs with power conversion efficiency (PCE) beyond 13% were achieved by structure improvement of the electron donor and choosingY6as the electron acceptor. However, the fill factor (FF) is an obstacle that limits the further improvement of the PCE for these ASM OSCs. Herein, we focus on the FF improvement of recently reported ASM OSCs withBTR-Cl:Y6as the active layer by miscibility-induced active layer morphology optimization. The incorporation of fullerene derivatives, which have good miscibility with bothBTR-ClandY6, results in reduced bimolecular recombination and thus improved FF. In particular, whenca.5 wt% ofPC(71)BMwas added in the active layer, a FF of 77.11% was achieved without sacrificing the open circuit voltage (V-OC) and the short circuit current density (J(SC)), leading to a record PCE of 15.34% (certified at 14.7%) for ASM OSCs. We found that the optimized device showed comparable charge extraction, longer charge carrier lifetime, and slower bimolecular recombination rate compared with those of the control devices (w/o fullerene). Our results demonstrate that the miscibility driven regulation of active layer morphology by incorporation of a fullerene derivative delicately optimizes the active layer microstructures and improves the device performance, which brings vibrancy to OSC research

Evaluation of the effects of forest management strategies on carbon sequestration in evergreen broad-leaved (Phoebe bournei) plantation forests using FORECAST ecosystem model

In the context of global climate change, it is critical to study how different forest management practices affect forest carbon sequestration. This is especially important for forest managers and policy makers who will have to design and implement appropriate mitigation and adaptation strategies. Previous research has focused on coniferous plantations with rare examination of plantations of evergreen broadleaved species. Phoebe bournei (Hemsley) Yang, as one of the representative species of subtropical evergreen broadleaf forests in Asia, has a unique potential to increase forest carbon sink. In this study, field data were combined with the forest ecosystem management model FORECAST to estimate the impacts of different forest management strategies (combinations of planting densities from 1000 to 4000 trees ha-1, rotation lengths from 20 to 80 years, and different harvesting intensities: stem-only, whole-tree and complete-tree) on carbon sequestration of Phoebe bournei plantations in south-eastern China. Field and previously published data were used to calibrate the model for stand biomass pools accumulation, stand density and mortality, light response curves, photosynthetic efficiency, and data on soil nutrient pools, for three different site conditions. The results showed that the most suitable planting density to maximize carbon sequestration in Phoebe bournei plantations is 2000-3000 trees ha-1. Long rotations (80 years) are better than shorter rotations (20 or 30 years) for the long-term maintenance of site productivity, though the recommended rotation length for maximizing carbon sequestration and maintaining forest productivity is 40-60 years. As for harvesting intensity, stem-only harvesting is the most suitable strategy to manage for carbon sequestration when maintaining long-term site productivity, with whole-tree and complete-tree harvesting constituting less optimal options. Our modelling exercise indicates that Phoebe bournei plantations have great potential for carbon sequestration if they are managed under sustainable and ecologically-based strategies. Given that forests are important in the global carbon cycle, it is recommended that afforestation efforts in relevant sub-tropical regions use appropriate broad-leaved species that can help resolve ecological and socio-economic challenge

Effects of Fluorination on Fused Ring Electron Acceptor for Active Layer Morphology, Exciton Dissociation, and Charge Recombination in Organic Solar Cells

Fluorination is one of the effective approaches to alter the organic semiconductor properties that impact the performance of the organic solar cells (OSCs). Positive effects of fluorination are also revealed in the application of fused ring electron acceptors (FREAs). However, in comparison with the efforts allocated to the material designs and power conversion efficiency enhancement, understanding on the excitons and charge carriers' behaviors in high-performing OSCs containing FREAs is limited. Herein, the impact of fluorine substituents on the active layer morphology, and therefore exciton dissociation, charge separation, and charge carriers' recombination processes are examined by fabricating OSCs with PTO2 as the donor and two FREAs, O-IDTT-IC and its fluorinated analogue O-IDTT-4FIC, as the acceptors. With the presence of O-IDTT-4FIC in the devices, it is found that the excitons dissociate more efficiently, and the activation energy required to split the excitons to free charge carriers is much lower; the charge carriers live longer and suffer less extent of trap-assisted recombination; the trap density is 1 order of magnitude lower than that of the nonfluorinated counterpart. Overall, these findings provide information about the complex impacts of FREA fluorination on efficiently performed OSCs

Self-assembly enables simple structure organic photovoltaics via green-solvent and open-air-printing: Closing the lab-to-fab gap

The ultimate goal of organic solar cells (OSCs) is to deliver cheap, stable, efficient, scalable, and eco-friendly solar-to-power products contributing to the global carbon neutral. However, simultaneously balancing these five critical factors of OSCs toward commercialization is extremely challenging. Herein, a green-solvent-processable and open-air-printable self-assembly strategy is demonstrated to synchronously simplify the device architecture, improve the power conversion efficiency (PCE) and enhance the shelf, thermal as well as light illumination stability of OSCs. The cathode interlayer (CIL)-free self-assembled OSCs exhibit the PCE of 15.5%, higher than that of traditional inverted OSCs of 13.0%, which is among the top values for both CIL-free self-assembled OSCs and open-air blade-coated bulk-heterojunction OSCs. The remarkable enhancements are mainly ascribed to the finely selfassembly, subtly controlled donor/acceptor aggregation rate, and delicately manipulated vertical morphology. Besides, this strategy enables 13.2% efficiency on device area of 0.98 cm(2), implying its potential for scalability. These findings demonstrate that this strategy can close the lab-to-fab gap of OSCs toward commercialized cheap, stable, efficient, scalable, and eco-friendly OSCs