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4,942 results on '"Lu, Zhen"'

61. Structural Origin of Boson Peak in Glasses

Author

Tian, Yuan, Shen, Xiaozhe, Gao, Qingyang, Lu, Zhen, Yang, Jie, Zheng, Qiang, Aleman, Christopher Florencio, Luo, Duan, Reid, Alexander Hume, Xu, Bin, Falk, Michael, Sheng, Howard, Cao, Jianming, Wang, Xijie, and Chen, Mingwei

Subjects
Condensed Matter - Disordered Systems and Neural Networks, Condensed Matter - Materials Science
Abstract

Boson peak, the excess low energy excitations in the terahertz regime, is one of the most unique features of disordered systems and has been linked to many anomalous properties of glass materials. The nature and structural origin of the boson peak remain elusive and have been debated for more than a half century mainly due to the lack of real-time and real-space experimental insights of the dynamic phenomenon. In this work we employed femtosecond MeV ultrafast electron diffraction to characterize the atomic dynamics of metallic glasses in real time. The experiment reveals collective atomic oscillations, presented in elastic electron scattering and atomic pair distribution functions, within the boson peak frequency range of 1.0-1.8 THz in both reciprocal and real space. It was found that the oscillation frequency has reciprocal dependence on interatomic pair distances and the corresponding wave velocity experimentally affirms the transverse acoustic wave nature of the boson peak. The observed strong correlation between THz acoustic vibrations and coherent electron scattering provides compelling evidence that the boson peak originates from the collective transverse vibrational modes of structurally ordered atoms in the disordered system.

Published
2021

62. Crystal-like Order Stabilizing Glasses: Structural Origin of Ultra-stable Metallic Glasses

Author

Lu, Zhen, Lu, Anh Khoa Augustin, Zhang, Fan, Tian, Yuan, Jiang, Jing, Wei, Daixiu, Han, Jiuhui, Gao, Qingyang, Ohara, Koji, Kato, Hidemi, Hirata, Akihiko, and Chen, Mingwei

Subjects
Condensed Matter - Disordered Systems and Neural Networks
Abstract

Glasses are featured with a disordered amorphous structure, being opposite to crystals that are constituted by periodic lattices. In this study we report that the exceptional thermodynamic and kinetic stability of an ultra-stable binary ZrCu metallic glass, fabricated by high-temperature physical vapor deposition, originates from ubiquitous crystal-like medium range order (MRO) constituted by Voronoi polyhedron ordering with well-defined local translational symmetry beyond nearest atomic neighbors. The crystal-like MRO significantly improves the thermodynamic and kinetic stability of the glass, which is in opposition to the conventional wisdom that crystal-like order deteriorates the stability and forming ability of metallic glasses. This study unveils the structural origin of ultra-stable metallic glasses and shines a light on the intrinsic correlation of local atomic structure ordering with glass transition of metallic glasses.

Published
2021

70. Investigation of nanoparticles in Enhanced Oil Recovery

Author

Lu, Zhen, Diaz, P., and Kellici, S.

Abstract

Most of the global oil production is achieved by water flooding (secondary oil recovery). However, in order to increase oil recovery factor, it is important to lower oil water interfacial tension to make oil and water to be more miscible; it is also important to alter rock wettability in natural or oil-wet reservoir conditions to make oil more detachable from rock surface. Conventionally, these are achieved by enhanced oil recovery technologies, e.g., thermal flooding and chemical flooding. However, these technologies are limited by their high energy consumption, high cost, undesirable stability in high salinity, and high environmental damage. In this research, novel materials of carbon-based nanoparticles (carbon quantum dots, CQDs) and a set of nanocomposites (hybrids of titanium dioxide and carbon-based nanoparticles) were developed and tested in EOR. The investigated materials were discovered to increase oil recovery through different mechanisms including not only IFT reduction and wettability alteration, but also temporary log-jamming (applicable when using CQDs in EOR). All materials investigated in this project were ready synthesised using a novel continuous hydrothermal flow synthesis system. CHFS provides a consistent, rapid, continuous production process by using supercritical water and a flow system. The reaction can be controlled by altering reaction pressure, temperature, reactants' concentration, and flow rate. CQDs studied in this research was functionalised by p-sulfonic acid calix[4]arene and the particle size was controlled to an extremely small level of 1.76 nm + 0.36 nm. This small size provides CQDs the ability to pass though ultra-tight porous media in rocks, and potentially cause temporary log-jamming to increase oil sweeping efficiency. To select the best nanocomposite, a set of TiO2-carbonaceous nanocomposites consisting of TiO2, carbon quantum dots (synthesised from two different carbon resources - citric acid or glucose), and reduced graphene oxide, were screened. The screening methodologies included different characterisations methods such as of zeta potential, IFT, and wettability measurement. From these studies was concluded that TiO2-graphene nanocomposite exhibited the most promising properties for EOR. In summary, both CQDs and TiO2-graphene nanocomposite could significantly increase oil recovery efficiency in EOR. A maximum of 17 ± 0.2% additional oil was recovered in core flooding using low CQDs concentration of 0.01 wt% in high salinity condition of 90000 ppm brine; and a relatively high incremental oil recovery factor of approx. 62% was achieved by TiO2-graphene nanocomposite in core flooding. A number of mechanisms have been investigated to understand the effect of nanoparticles in oil recovery. It was found that temporary log-jamming appears to be the main mechanism for CQDs in EOR, as pressure increases were associated with additional oil production. Whereas for TiO2-graphene nanocomposite, interfacial tension reduction and wettability alteration are the main mechanisms that explain the experimental results.

Published
2022
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76. Impact factors of Blastocystis hominis infection in persons living with human immunodeficiency virus: a large-scale, multi-center observational study from China

Author

Zhang, Shun-Xian, Wang, Ji-Chun, Li, Zhong-Wei, Zheng, Jin-Xin, Zhou, Wen-Ting, Yang, Guo-Bing, Yu, Ying-Fang, Wu, Xiu-Ping, Lv, Shan, Liu, Qin, Chen, Mu-Xin, Lu, Yan, Dou, Zhi-Hui, Zhang, Da-Wei, Lv, Wen-Wen, Wang, Lei, Lu, Zhen-Hui, Yang, Ming, Zheng, Pei-Yong, Chen, Yue-Lai, Tian, Li-Guang, and Zhou, Xiao-Nong

Published
2023
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78. Immediate and long-term outcomes after treat-all among people living with HIV in China: an interrupted time series analysis

Author

Wu, Xinsheng, Wu, Guohui, Ma, Ping, Wang, Rugang, Li, Linghua, Sun, Yinghui, Xu, Junjie, Li, Yuwei, Zhang, Tong, Li, Quanmin, Yang, Yuecheng, Wang, Lijing, Xin, Xiaoli, Qiao, Ying, Fang, Bingxue, Lu, Zhen, Zhou, Xinyi, Chen, Yuanyi, Liu, Qi, Fu, Gengfeng, Wei, Hongxia, Huang, Xiaojie, Su, Bin, Wang, Hui, and Zou, Huachun

Published
2023
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100. A predictive model of the turbulent burning velocity for planar and Bunsen flames over a wide range of conditions

Author

Lu, Zhen and Yang, Yue

Subjects
Physics - Fluid Dynamics
Abstract

We propose a predictive model of the turbulent burning velocity over a wide range of conditions. The model consists of sub models of the stretch factor and the turbulent flame area. The stretch factor characterizes the flame response of turbulence stretch and incorporates effects of detailed chemistry and transport with a lookup table of laminar counterflow flames. The flame area model captures the area growth based on Lagrangian statistics of propagating surfaces, and considers effects of turbulence length scales and fuel characteristics. The present model predicts the turbulent burning velocity via an algebraic expression without free parameters. It is validated against 285 cases of the direct numerical simulation or experiment reported from various research groups on planar and Bunsen flames over a wide range of conditions, covering fuels from hydrogen to n-dodecane, pressures from 1 to 20 atm, lean and rich mixtures, turbulence intensity ratios from 0.35 to 110, and turbulence length ratios from 0.5 to 80. The comprehensive comparison shows that the proposed turbulent burning velocity model has an overall good agreement over the wide range of conditions, with the averaged modeling error of 25.3%. Furthermore, the model prediction involves the uncertainty quantification for model parameters and chemical kinetics to extend the model applicability., Comment: 37 pages, 16 figures

Published
2021
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