Search

On the turbocharger, two forms of intake pipe, bending and torsion, are usually used, which leads to a vortex at the inlet of the blade. It has been found that double vortices and massive vortices play a significant role in the working characteristics of the compressor. This project intends to conduct a systematic theoretical and experimental study on the effects of vortex deformation under two different working conditions of bending and torsion on the internal flow field, tip leakage flow field, and impeller load of the impeller. It has been found that the presence of a vortex near the blade entrance changes the static pressure and inflow angle near the blade entrance. The reverse transfer of vortex flow and vortex flow caused by vortex has three critical effects on the working characteristics of the compressor: 1. The change of circumferential static pressure and the pressure gradient of the flow in the impeller. 2. The location and density of the leakage flow on the top surface are significantly changed. 3. Adjust the impeller load’s change and fluctuation when it rotates.

The geometry of the vortex shell significantly affects the non-axisymmetric flow in centrifugal compressors. This study explores the static pressure characteristics of the vortex shell through experimental data and numerical analysis using finite element software. Findings indicate that the vortex tongue region critically influences the cascade structure. At high flow rates (0.40 kg/s), flow field parameters at the blade and vortex shell inlets alter markedly near the tongue side. Conversely, at lower velocities (0.26 kg/s), flow distribution at the blade inlet becomes more uneven, and changes in the inflow angle are more pronounced. Additionally, blade pulsation intensifies at higher velocities, and the jet wake vortex exhibits structural variations at different velocities. High-pressure fluctuations are notably transmitted upwards through the vortex shell, with periodic fluctuations affecting the impeller load. These changes significantly impact the flow field under various operating conditions.

Study region: This study focuses on the upper reaches of Shule river (URSLH) and Heihe river (URHH) basins and Taolai river (URTLH) basin in Qilian Mountains. Study focus: The impact of the cryosphere changes on runoff components in basins with different cryosphere ratios. New hydrological insights for the region: Total runoff (TR) increased in URSLH and URHH and decreased in URTLH, snowmelt runoff (SR) decreased in each basin, glacier runoff (GR) increased in URSLH and URTLH but decreased in URHH during 1980–2015. In the future, GR will increase under SSP585 and slightly decrease under SSP126 in 2040–2060 in URSLH and decrease in URHH and URSLH. The peak time of SR will advance by a month in each basin. In the future, GR (The ratio of the coefficient of variation (cv) of TR to cv of non-glacial runoff) will decrease, indicating hydrological regulation of glaciers will be weakened in these basins. SR and Rs (The ratio of summer runoff to spring runoff) will show downward trends, the processes of TR increase will be smoother. Rr (The ratio of maximum to minimum monthly runoff) will show downward trends under SSPs. TR will become smoother in each basin. Furthermore, the change of each runoff components will make TR tends to be smoother in the future and reduce TR especially in summer.

Domestic tourism demand has dominated the global tourism market and has been more resilient during the COVID-19 pandemic; yet, it is under-studied compared to international tourism demand. Digital financial inclusion (DFI) enables the provision of formal financial products and services to small and medium-sized tourism enterprises and tourists through cost-effective digital means, potentially boosting domestic tourism demand. Integrating micro- and macro-level data from 335 prefecture-level regions in China, we investigate the impact of DFI on domestic tourism demand using spatial panel models. Our analysis reveals significant and positive effects, both direct and spillover, of DFI on domestic tourism demand within a region and across regions. Notably, among the three dimensions of DFI, the usage depth exhibits the most substantial spillover effects. Furthermore, our findings also highlight the crucial role of DFI in internalizing domestic tourism revenues. Our study provides practical implications for sustainable domestic tourism development in the digital era. [ABSTRACT FROM AUTHOR]

The Yellow River Delta wetland is a habitat for wintering waterfowl, where mallard (Anas platyrhynchos) and tundra bean goose (Anser fabalis) are commonly observed. Although the intestinal flora plays a pivotal role in maintaining host health and promoting nutrient absorption, it remains unclear whether the same overwintering habitat and challenging feeding conditions specifically affect the composition and diversity of intestinal flora in both species. Here, high-throughput sequencing was used to compare the intestinal bacterial communities of mallard and tundra bean goose from the same region. There was no significant difference in alpha diversity and beta diversity between the two species. Firmicutes and Proteobacteria were the two predominant phyla, accounting for more than 50.00% of the total. They enhanced the nutrient absorption and metabolic efficiency during overwintering. Catellicoccus was the most dominant genus in the intestinal flora of tundra bean goose, accounting for 33.91%, whereas Clostridium sensu stricto 1 was the most dominant genus in mallard, accounting for 7.34%. This difference is considered to be related to the feeding habits of these two species. No significant differences in the structure and diversity of intestinal bacterial communities were observed between mallard and tundra bean goose, and the similarity of intestinal flora between them was high. This study deepens our understanding of the intestinal flora of two coexisting species with different dietary preferences in the Yellow River Delta. It also lays the foundation for waterfowl disease prevention in this area, carrying significant scientific and practical implications for biodiversity and ecosystem conservation. [ABSTRACT FROM AUTHOR]

An ultra-high-speed electric air compressor (UHSEAC) generates a load torque component during operation, leading to unstable output. As air passes through the UHSEAC, the air density changes significantly, resulting in increased uneven distribution. This causes rapid changes in gas parameters, making them difficult to extract. Consequently, the behavior of load torque component variations under ultra-high-speed operating conditions (UHSOC) remains unclear. The influence of UHSOC on the load torque component has not been studied. In this article, the fluid model of the UHSEAC is established and verified, and the load torque component is extracted based on this model. The influence of speed and torque on the load torque component under UHSOC is then studied. The results show that the frequency of the load torque component increases by 14.29% as the speed increases from 70,000 rpm to 90,000 rpm. Additionally, as the torque increases from 1.3 Nm to 1.7 Nm, the amplitude of the load torque component increases by 69.56%. These findings provide valuable guidance for future scholars seeking to optimize UHSEAC design to reduce load torque components. [ABSTRACT FROM AUTHOR]

Recently, low efficiency and stability due to unbalanced carrier injection remain urgent problems in inorganic quantum dot light†emitting diodes (QLEDs). To address these issues, the device was irradiated with ultraviolet light in this study, which improved the interface contact. This resulted in the smaller electron potential barrier, increased hole injection and more balanced carrier injection in the device. Ultimately, the device efficiency was improved, and the operating lifetime of the device was increased by ~91†fold. [ABSTRACT FROM AUTHOR]

In this work, efficient QD‐photosensitive ligand system were designed. By direct photolithography, RGB pixel arrays with a single sub‐pixel size of 39 um × 5 um were successfully prepared on patterned PM substrates. While illuminated separately, there were no residual QD emission peaks from neighbor sub‐pixel in electroluminescence spectra. Experience on the PM substrate guided the successful preparation of a 4.7‐inch 650 ppi AM‐QLED display. This was the first AM‐QLED prototype prepared by direct lithography. [ABSTRACT FROM AUTHOR]

In this paper the photolithgraphic patterning approaches of quantum dots in electroluminescent devices and demoes were summerized. Photolithograpy process meets the requirements for QLED mass production, including high pixel density, large‐area process and low cost. We summerized three approaches of quantum dot photolithographic procrsses, including direct photolithography, photolithography with lift‐off process and sacrificial layer assisted patterning (SLAP). [ABSTRACT FROM AUTHOR]

Solar radiation plays an important role in the cryospheric water cycle, especially in alpine regions. This study presents an evaluation of the Modern-Era Retrospective analysis for Research and Applications 2 (MERRA2), ERA5, High Asia Refined analysis version 2 (HAR v2), JRA-55, and National Centers for Environmental Prediction/Climate Forecast System Reanalysis datasets at different time scales by comparing observed datasets from July 2010 to December 2015 at 4,550 m in the Laohugou Basin. In terms of shortwave radiation, ERA5 performs significantly better than the other reanalysis radiation datasets. For downward shortwave radiation, HAR v2 performs better than ERA5 on only two timescales, 3 months and half-year, with mean absolute errors (MAEs) of 13.28 and 7.96 w/m2. The upward shortwave radiation, ERA5, outperforms the other reanalysis datasets on all 12 timescales. For downward longwave radiation, ERA5 also performs significantly better, with only MERRA2 outperforming ERA5 on the daily scale and annual scale, with R2, bias, root mean square error, and MAE of 0.6, 0.95, −9.51 w/m2, −9.41 w/m2, 34.98 w/m2, 9.46 w/m2, and 27.52 w/m2, 9.41 w/m2, respectively. In the upward longwave radiation, HAR v2 performs better than the other reanalysis datasets on all timescales, except for ERA5, which has a better R2 of 0.92 on the annual scale. All the reanalysis datasets can show the variation trend of the four radiation parameters in different seasons and achieve a better performance in winter. Therefore, ERA5 is recommended for regions without shortwave radiation observations, and HAR v2 and ERA5 are recommended for longwave radiation simulations. Although there are obvious shortcomings in the reanalysis radiation datasets, they still provide important supplementary information for research in high-altitude areas, where the observed datasets are too sparse.

Monitoring of aerodynamic parameters of the blade helps to enhance the operating capabilities of the Wells turbine. In this study, a few discrete pressure points were used to estimate the pressure patterns by fitting the exact potential-flow solution for flow over a parabola. The sectional aerodynamics was assessed by the leading-edge flow sensing (LEFS) algorithm. A characteristic parameter was employed to deduce leading-edge flow status. Moreover, the influence of rotor speeds and tip gaps on the vortex boundary was discussed in terms of the Lagrangian frame. For the rotor speed larger than 1000 rpm at the incipient stall point, there is no boundary layer separation at the suction side of the blade tip leading edge. At the same rotor speed, a large tip gap reduces the axial shear of the suction flows and the axial stretching of the tip leakage vortex, which helps to enhance the interaction time and strength of the leakage vortex and the suction flows. For the Wells turbine with attached flows, the LEFS algorithm can accurately evaluate the pressure distribution and suction parameters near the leading edge. The LEFS-derived dimensionless parameter can act as an equivalent angle of attack under different tip gaps, providing the possibility for stall warning of Wells turbines. [ABSTRACT FROM AUTHOR]

The ultra-high-speed electric air compressor (UHSEAC) is affected by the electromagnetic torque components of the ultra-high-speed permanent magnet synchronous motor (UHSPMSM) during wide-range speed regulation, resulting in intense speed fluctuation. Electromagnetic torque components are generated by the effects of permanent magnet field harmonics, stator slotting, and current harmonics. It is very important to conduct simulation comparisons and theoretical descriptions of different sources of pulsation factors. In this paper, firstly, the electromagnetic torque model of UHSPMSM with a rated speed of 80,000 rpm is constructed and verified by an experimental bench. Secondly, the electromagnetic torque components of UHSPMSM are extracted on the basis of the electromagnetic torque model. Finally, the electromagnetic torque components' characteristic law is investigated under different ultra-high-speed operating conditions. The results show that under ultra-high-speed operation, the frequency and amplitude of electromagnetic torque components become larger with increasing speed. And the amplitude of electromagnetic torque components becomes larger with increasing torque. This paper constructs the observation object of the high-frequency state observer and does the preliminaries for the design of the UHSEAC controller. [ABSTRACT FROM AUTHOR]

In this work, a highly efficient photosensitive quantum dot (QD) system was designed. The optimized photosensitive QD system had high photoluminescence quantum yield and colloidal stability. By direct photolithography, RGB pixel arrays with a single sub‐pixel size of 39 μm × 5 μm were successfully prepared. Further, the full‐color QLED device was realized. There were no residual QD emission peaks from neighboring sub‐pixels observed in the electroluminescence spectra. Experience on the full‐color QLED device guided the successful preparation of a 4.7‐inch 650 PPI active matrix QLED prototype. The active matrix QLED prototype could display clear and complete pictures. The color gamut reached 85% of the BT2020 standard. This is the first active matrix QLED prototype prepared with a record‐high resolution by direct photolithography, which promoted the development of QLED display technology. [ABSTRACT FROM AUTHOR]

The global tourism industry is struggling to recover from the COVID-19 pandemic. During the COVID-19 pandemic, daily tourism forecasting is more critical than ever before in supporting decisions and planning. Considering the changes in tourist psyche and behaviour caused by COVID-19, this study attempts to investigate whether the statistical modelling methods can work reliably under the new normal when travel restrictions are eased or lifted. To this end, we first compare the predictivity of daily tourism demand data before and during COVID-19, and observe heterogeneous impacts across different geographical scales. Then an improved multivariate & multiscale decomposition-ensemble framework is proposed to forecast daily tourism demand. The empirical study indicates the superiority and practicability of the proposed framework before and during COVID-19. Finally, we call for more research on the comparability of tourism demand forecasting. [ABSTRACT FROM AUTHOR]