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163 results on '"Han, Yehua"'

15. Structural insights into variation of intramolecular acid site using phase transition experiments and computation.

Author

Fu, Dali, Wang, Haodong, Wang, Tan, Xu, Chunming, and Han, Yehua

Subjects
PHASE transitions, ION mobility spectroscopy, CHEMICAL engineering, CHEMICAL processes, QUANTUM chemistry, MASS transfer
Abstract

Mass transfer from liquid to gas phase is a crucial process in chemical engineering. Due to the heterogeneity and dynamic nature of the phase transition process, monitoring the structural changes of compounds during this process is challenging. In this work, a combining of the mass spectrometry‐based method and quantum chemistry calculations was used to study the structural changes during liquid‐to‐gas phase transitions. Electrospray is used to induce the transition of phenolic acid molecules from the liquid phase to the gas phase. The deprotonated structures were captured and separated using ion mobility mass spectrometry. Deprotonated structures helped to identify the most acidic functional group within the molecule. These deprotonated structures were confirmed by collision‐induced dissociation and molecular collision cross‐section measurements. Quantum chemistry calculations revealed the mechanisms about the variation of intramolecular acid site and "kinetic trapping." Three liquid‐to‐gas phase transformation models were proposed, demonstrating that the variation in free energy among different deprotonated structures governs the thermodynamic/kinetic process of the liquid‐to‐gas phase conversion. [ABSTRACT FROM AUTHOR]

Published
2024
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25. Pressure-Induced Hydrogen Transfer in 2-Butyne via a Double CH···π Aromatic Transition State

Author

Zhang, Peijie, primary, Tang, Xingyu, additional, Zhang, Chunfang, additional, Gao, Dexiang, additional, Wang, Xuan, additional, Wang, Yajie, additional, Guo, Wenhan, additional, Zou, Ruqiang, additional, Han, Yehua, additional, Lin, Xiaohuan, additional, Dong, Xiao, additional, Li, Kuo, additional, Zheng, Haiyan, additional, and Mao, Ho-kwang, additional

Published
2022
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33. Detailed Oscillation Analysis and Parameter Selection Principle for Boost PFC Converter With RC Snubber Operated in DCM

Author

Kai Yao, Hairui Xu, Ke Yun, Qiang Li, and Han Yehua

Subjects
Physics, Total harmonic distortion, Oscillation, 020208 electrical & electronic engineering, 02 engineering and technology, Power factor, Inductor, Inductance, Parasitic capacitance, Control theory, Parasitic oscillation, 0202 electrical engineering, electronic engineering, information engineering, Snubber, Electrical and Electronic Engineering
Abstract

The parasitic parameters of a boost power factor correction converter lead to input current distortion when the converter operates in discontinuous conduction mode, and using an RC snubber is a simple and effective way to suppress the parasitic oscillation. The effect of the RC snubber on the parasitic oscillation is analyzed in detail, and three different forms of the characteristic roots are obtained according to different RC values. The optimal RC values and their relationship between the inductance and parasitic capacitance are figured out, which can achieve a lowest total harmonic distortion. A 1-kW prototype has been built and tested at low power and the experimental waveforms and data are presented to validate the theoretical analysis.

Published
2019

37. Monolithic superhydrophobic polymer layer with photopatterned virtual channel for the separation of peptides using two-dimensional thin layer chromatography-desorption electrospray ionization mass spectrometry

Author

Han, Yehua, Levkin, Pavel, Abarientos, Irene, Liu, Huwei, Svec, Frantisek, and Frechet, Jean M.J.

Subjects
Polymerization -- Usage, Mass spectrometry -- Methods, Peptides -- Properties, Thin layer chromatography -- Methods, Chemistry
Abstract

Superhydrophobic monolithic porous polymer layers with a photopatterned hydrophilic channel have been prepared. These layers were used for two-dimensional thin layer chromatography of peptides. The 50 [micro]m thin poly(butyl methacrylate-co-ethylene dimethacrylate) layers supported onto 4.0 x 3.3 cm glass plates were prepared using UV-initiated polymerization in a simple glass mold. Photografting of a mixture of 2-acrylamido-2-methyl-1-propanesulfonic acid and 2-hydroxyethyl methacrylate carried out through a mask afforded a 600 [micro]m wide virtual channel along one side of the layer. This channel, which contains ionizable functionalities, enabled the first dimension separation in ion exchange mode. The aqueous mobile phase migrates only through the channel due to the large difference in surface tension at the interface of the hydrophilic channel and the superhydrophobic monolith. The unmodified part of the layer featuring hydrophobic chemistry was then used for the reversed phase separation in the orthngonal second dimension. Practical application of our technique was demonstrated with a rapid 2D separation of a mixture of model peptides differing in hydrophobicity and isoelectric point using a combination of ion-exchange and reversed phase modes. In the former mode, the peptides migrated 11 mm in less than 1 min. Detection of fluorescently labeled peptides was achieved through UV light visualization. Separation of the native peptides was monitored directly using a desorption electrospray ionization (DESI) source coupled to a mass spectrometer. Unidirectional surface scanning with the DESI source was found suitable to determine both the location of each separated peptide and its molecular mass. 10.1021/ac100010h

Published
2010

40. A Series Diode Method of Suppressing Parasitic Oscillation for Boost PFC Converter Operated in Discontinuous Conduction Mode

Author

Hairui Xu, Kai Yao, Junchao Song, Han Yehua, and Qiang Li

Subjects
Series (mathematics), Oscillation, 020208 electrical & electronic engineering, 05 social sciences, 02 engineering and technology, Power factor, Inductor, Control theory, Parasitic oscillation, Distortion, 0502 economics and business, 0202 electrical engineering, electronic engineering, information engineering, 050211 marketing, Electrical and Electronic Engineering, Current (fluid), Mathematics, Diode
Abstract

When a boost power factor correction converter operates in a discontinuous conduction mode, the nonzero characteristic of the average current in oscillation period and the initial value of the inductor current in a switching cycle are the main cause of the influence of the parasitic parameters on input current distortion. The effect of parasitic parameters oscillation is analyzed in detail, and a new method of series diode is proposed, which can effectively decrease the input current distortion and improve the power factor. Selection principles of series diode are given. Experimental results verify the correctness and the feasibility of the theoretical analysis.

Published
2018

47. Analytical strategies for chemical characterization of bio‐oil.

Author

Wang, Yinghao, Han, Yehua, Hu, Wenya, Fu, Dali, and Wang, Gang

Subjects
*CHEMICAL transportation, *NUCLEAR magnetic resonance spectroscopy, *MASS spectrometry, *ALTERNATIVE fuels, *RAW materials, *FURFURAL, *LIGNOCELLULOSE
Abstract

Bio‐oils, produced by biomass pyrolysis, have become promising candidates for feedstocks of high value‐added chemicals and alternative sources for transportation fuels. Bio‐oil is such a complicated mixture that contains nonpolar hydrocarbons and polar components which cover almost all kinds of organic oxygenated compounds such as carboxylic acids, alcohols, aldehydes, ketones, esters, furfurals, phenolic compounds, sugar‐like material, and lignin‐derived compounds. Comprehensive characterization of bio‐oil and its subfractions could provide insight into the conversion process of biomass processing, as well as its further utilization as transportation fuels or chemical raw materials. This review focuses on advanced analytical strategies on in‐depth characterization of bio‐oil, which is concerned with gas chromatography, high‐resolution mass spectrometry, FTIR spectroscopy and NMR spectroscopy, offering complementary information for previous reviews. [ABSTRACT FROM AUTHOR]

Published
2020
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