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927 results on '"He, Qiao"'

3. Photocatalytic doping of organic semiconductors

Author

Jin, Wenlong, Yang, Chi-Yuan, Pau, Riccardo, Wang, Qingqing, Tekelenburg, Eelco K., Wu, Han-Yan, Wu, Ziang, Jeong, Sang Young, Pitzalis, Federico, Liu, Tiefeng, He, Qiao, Li, Qifan, Huang, Jun-Da, Kroon, Renee, Heeney, Martin, Woo, Han Young, Mura, Andrea, Motta, Alessandro, Facchetti, Antonio, Fahlman, Mats, Loi, Maria Antonietta, and Fabiano, Simone

Published
2024
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14. A numerical study on hydrogen blending in natural gas pipeline by a T-Pipe

Author

Ouyang Xin, He Qiao, Chai Chong, Wang Yeqin, Di Tao, Zhou Jingwei, and Sun Xu

Subjects
Natural gas pipeline, Hydrogen-methane blending, Gas stratification, Large eddy simulation, Engineering (General). Civil engineering (General), TA1-2040
Abstract

In order to study the flow blending and transporting process of hydrogen that injects into the natural gas pipelines, a three-dimensional T-pipe blending model is established and the flow characteristics are investigated systematically by the large eddy simulation (LES). Firstly, the mathematical formulation of hydrogen-methane blending process is provided and the LES method is introduced and validated by a benchmark gas blending model having experimental data. Subsequently, the T-pipe blending model is presented, and the effects of key parameters, such as the velocity of main pipe, hydrogen blending ratio, diameter of hydrogen injection pipeline, diameter of main pipe and operating pressure on the hydrogen-methane blending process, are studied systematically. The results show that, under certain conditions, the gas mixture will be stratified downstream of the blending point, with hydrogen at the top of the pipeline and methane at the bottom of the pipeline. In the no-stratified scenario, the mixing distance increases at lower hydrogen mixing ratio and larger diameter of the hydrogen injection pipe or the main pipe. Finally, based on the numerical results, the underlying physics of the stratification phenomenon during the blending process are explored and an indicator for stratification is proposed using the ratio between the Reynolds numbers of the natural gas and hydrogen.

Published
2024
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19. Electromagnetic Fields Induced by Three-Dimensional Short Ocean Waves in a Horizontally Layered Seabed

Author

Ronghua Tao, Baoqiang Zhang, Chun Zhou, and He Qiao

Subjects
Electromagnetic fields, frequency spectrum, motional induction, ocean waves, time series, Electrical engineering. Electronics. Nuclear engineering, TK1-9971
Abstract

An accurate model is needed to simulate the electromagnetic fields induced by short-period ocean waves to study the influence of the induced fields on the data set of marine magnetotelluric (mMT), marine controlled source electromagnetic (mCSEM), and marine airborne (low altitude) magnetic anomaly detection (MAD). By using a three-dimensional (3-D) linear wave model and directly solving linear equations derived from Maxwell’s equations and boundary conditions of a horizontal layered seabed, we obtained analytical solutions of the six components of the electromagnetic fields induced by three components of the velocity of ocean waves and three components of geomagnetic fields. In addition to horizontal currents induced by the horizontal velocity and vertical geomagnetic field, the contributions from the horizontal current induced by the vertical velocity and horizontal geomagnetic field and vertical current were considered in the governing equations. On the basis of the solutions, we studied how the geomagnetic field and wind fields affect the relationship between the two horizontal components and between the horizontal and vertical components of the electromagnetic fields at the sea surface. We simulated the influence of water depth and wind fields on the distribution of the spectrum and time series of the induced fields by using a typical wave spectrum and directional spectrum. Finally, the possibility of detecting seafloor conductivity structures by using the electromagnetic response of short ocean waves was also discussed.

Published
2024
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49. Synthesis and optoelectronic properties of electron accepting materials in organic photovoltaics

Author

He, Qiao and Heeney, Martin

Abstract

Remarkable advances have been seen in the area of organic photovoltaics (OPVs), with the power conversion efficiencies (PCEs) doubling in the past four year and exceeding over 18%. The commercial potential of OPV technology has been demonstrated, partly due to the fast development of new electron accepting materials. Although fullerene derivatives possess excellent electron mobility and affinity, they have some intrinsic limitations, including weak absorption in the visible region, elevated synthetic difficulty in tuning the electronic/optical properties, and poor morphology stability. Developing new electron acceptors to further improve the performance (including efficiency and stability) of OPV cells is necessary. This thesis focuses on the synthesis and charsterisation of novel electron accepting materials. Initially star-shaped oligomers were developed, however precise modulation of the molecular structure was needed to achieve proper energetics and high electron mobility. The unfavorable morphology, blended with electron donating materials, appeared to be another reason that limited the device performance. By combination of a benzodithiophene core and four diketopyrrolopyrrole arms, an oligomer was developed, which exhibited better p-type (electron donating) behavior in both OPV and organic field-effect transistor devices. Perylene diimide tetramers were developed to construct new electron acceptors and the broad absorption spectrum shown in ring-fused molecule was first explained by time-dependent density function theory (TD-DFT) calculations. In addition, linear ladder-type molecules were explored. Via a facile aromatic extension strategy, cyclopentadithienothiophene was prepared as a bent small molecule acceptor, which demonstrated promising device performance with high short-circuit current. Fully alkylated dithienocyclopentacarbazole flanked by electronwithdrawing nonfluorinated or fluorinated 1,1-dicyanomethylene-3-indanone were developed to investigate the effect of side chains and fluorination. Compared to the electron acceptor with bulky arylalkyl chains, alkyl side chains were found to enhance molecular packing and crystallinity and fluorination led to a more optimal nanoscale blend morphology and high performance. Finally, two wide-bandgap acceptors were developed for front-cell materials in tandem solar cells. High PCEs were achieved and in excellent agreement with theoretical simulations.

Published
2021
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