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4,271 results on '"Zhi Tao"'

206. Imaging of granular sources in high energy heavy ion collisions

Author

Yang, Zhi-Tao, Zhang, Wei-Ning, Huo, Lei, and Zhang, Jing-Bo

Subjects
High Energy Physics - Phenomenology
Abstract

We investigate the source imaging for a granular pion-emitting source model in high energy heavy ion collisions. The two-pion source functions of the granular sources exhibit a two-tiered structure. Using a parametrized formula of granular two-pion source function, we examine the two-tiered structure of the source functions for the imaging data of Au+Au collisions at Alternating Gradient Synchrotron (AGS) and Relativistic Heavy Ion Collider (RHIC). We find that the imaging technique introduced by Brown and Danielewicz is suitable for probing the granular structure of the sources. Our data-fitting results indicate that there is not visible granularity for the sources at AGS energies. However, the data for the RHIC collisions with the selections of $40 < {\rm centrality} < 90%$ and $0.20

Published
2008
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208. Advanced orthogonal frequency and phase modulated waveform for contrast-enhanced photothermal wave radar thermography.

Author

Luo, Zhi-Tao, Shen, Peng, Luo, Hao, Wang, Sheng, Wu, Xin-Kai, and Zhang, Hui

Subjects
*THERMOGRAPHY, *RADAR, *NONDESTRUCTIVE testing, *MIMO radar, *THERMAL conductivity, *SIGNAL-to-noise ratio, *CARBON fibers
Abstract

Thermal wave radar (TWR) thermography is a high-efficient nondestructive testing technique to increase the signal-to-noise ratio (SNR) and to enhance target detection capability. However, the detection of subsurface defects, especially small-size defects, usually requires a distinctively high SNR and depth resolvability. This paper proposed an orthogonal phase-coded linear frequency modulated (OPCLFM) excitation waveform, which has significantly improved the SNR and depth resolvability of TWR compared to the LFM waveform. The pulse compression quality of the OPCLFM waveform was initially evaluated through a 1D thermal wave analytical model of carbon fiber reinforced polymer (CFRP) laminate. Results show that the OPCLFM waveform combined with the Kaiser window function compresses the largest sidelobe at least by 18.39 dB compared to the LFM waveform. Furthermore, the superior depth resolvability performance of the OPCLFM waveform was also validated by 3D finite element simulation. Finally, the effect of thermal conductivity on the depth resolvability performance of the OPCLFM waveform was evaluated quantitatively by a delaminated CFRP laminate. [ABSTRACT FROM AUTHOR]

Published
2022
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220. UHMWPE/Organoclay Nanocomposites Fabricated by Melt Intercalation Under Continuous Elongational Flow: Dispersion, Thermal Behaviors and Mechanical Properties

Author

Lin, Wangyang, Hou, Aolin, Feng, Yan-Hong, Yang, Zhi-Tao, and Qu, Jin-Ping

Subjects
Polyethylene -- Thermal properties -- Mechanical properties, Clay -- Thermal properties -- Mechanical properties, Composite materials -- Production processes -- Thermal properties -- Mechanical properties, X-ray diffraction, Microscopy, Electron microscopy, Novels, Montmorillonite, Engineering and manufacturing industries, Science and technology
Abstract

The preparation of ultra-high-molecular weight polyethylene (UHMWPE)/organoclay nanocomposites by continuous elongational flow technique was investigated in a novel eccentric rotor extruder (ERE). The distribution and dispersion morphologies of organo-modified montmorillonite (OMMT) layers were revealed and observed by ash determination, wide angle X-ray diffraction and transmission electron microscopy. The thermal and thermal-mechanical behaviors were characterized by differential scanning calorimeter, thermal gravimetric analysis and dynamic mechanical thermal analysis. The mechanical performances was measured by tensile and impact test. The morphologies of the nanocomposites evidenced that the OMMT layers can be well intercalated or/and exfoliated by UHMWPE matrix, then the fabrication mechanism of intercalated and exfoliated OMMT structures under continuous elongational flow was discussed. The ideal dispersion of OMMT in UHMWPE matrix obviously improved the crystallinity and the mechanical properties at a certain concentration of OMMT loading, indicating that the lower OMMT addition can lead an effective strengthening and toughening for UHMWPE., INTRODUCTION Ultra-high-molecular weight polyethylene (UHMWPE) is a widely applied thermoplastic polymer with low friction coefficient, excellent impact resistance and chemical stability as well as recognized biocompatibility [1-6]. However, the ordinary [...]

Published
2019
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221. Roles of the Microbiota of the Female Reproductive Tract in Gynecological and Reproductive Health

Author

Bin Zhu, Zhi Tao, Laahirie Edupuganti, Myrna G. Serrano, and Gregory A. Buck

Subjects
Infectious Diseases, Reproductive Health, Pregnancy, Microbiota, Vagina, Infant, Newborn, Humans, Premature Birth, Female, Biodiversity, Molecular Biology, Microbiology
Abstract

The microbiome of the female reproductive tract defies the convention that high biodiversity is a hallmark of an optimal ecosystem. Although not universally true, a homogeneous vaginal microbiome composed of species of Lactobacillus is generally associated with health, whereas vaginal microbiomes consisting of other taxa are generally associated with dysbiosis and a higher risk of disease.

Published
2023

232. Wellbore Temperature Field During Cementing Pumping

Author

Rui Zheng, Zhao Huang, Zhi-Tao Chen, Si-Da Cheng, Yong Li, and Hai-Sheng Jin

Subjects
Mechanical Engineering, Energy Engineering and Power Technology
Abstract

Summary To plan cementing operations in oil wells, predicting accurate circulating temperature is required. Failure to predict the circulating temperature can result in the wrong thickening time. To the best of our knowledge, correlation of the tables in API Recommended Practice 10B are usually chosen to predict bottomhole circulating temperature (BHCT), but both are not suitable in every block with a different geological condition. To design thickening time of the cement slurry, it is necessary to give a credible temperature profile of the wellbore during cementing pumping. Accordingly, a heat transfer numerical model has been developed to simulate conditions encountered down hole. To be accurate, the thermal conductivities and the specific heat of the mud, the spacer, and the cement slurry have been tested. The circulating temperature encountered by the cement slurry rises with the drop of the rate, the increase of the lateral section, the decrease of the slurry density, the decrease of the slurry thermal conductivity, and the decrease of the slurry-specific heat. The simulated data agree with the data obtained from the field case. The heat-up process of the cement slurry in simulation is different from that in the API thickening-time test. To analyze the impact of heat-up process on thickening time, two tests were designed. The results show that the heat-up process has a significant impact on the thickening time. Therefore, the method given by API has some limitations. The wellbore temperature field during cementing pumping was analyzed, and the real-time temperature of fluid was tracked, which supports the cementing design optimization and job safety, also improving bonding quality.

Published
2023

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