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258 results on '"Yan, Liwen"'

64. Preparation and Properties of Highly Elastic, Lightweight, and Thermally Insulating SiO 2 Fibrous Porous Materials.

Author

Li, Yitian, Guo, Anran, Xu, Xiaojing, Xue, Yunjia, Yan, Liwen, Hou, Feng, and Liu, Jiachen

Subjects
POROUS materials, ELASTICITY, HEAT treatment, SLURRY, INSULATING materials, ZETA potential
Abstract

Fibrous porous materials are one of the most commonly used high-temperature insulation materials because of their high porosity and low thermal conductivity. Due to their wide applications in the aerospace and energy industries, the investigation of high-elastic thermally insulating porous materials has attracted increasing attention. In order to improve the elasticity of fibrous porous materials, quartz fibers with high aspect ratio were used as matrix, sodium hexametaphosphate (SHMP) was selected as dispersant. We innovatively reported that a unique three-dimensional skeleton structure was constructed by adjusting the dispersion of fibers in the slurry, and the lightweight, thermal insulating and elastic SiO2 fibrous porous material was then prepared by the compression molding method. The characterization results of zeta potential and absorbance showed that the addition of SHMP was an effective method to enhance the dispersibility of quartz fibers in the slurry. SiO2 fibrous porous materials with 0.4 wt% SHMP content exhibited an ideal three-dimensional skeleton structure, which endowed the porous material with high porosity (89.39%), low density (0.04751 g/cm3), and low thermal conductivity (0.0356 W·m−1·K−1). The three-dimensional skeleton structure formed by overlapping fibers with high aspect ratios endowed the porous material with excellent elasticity. SiO2 fibrous porous materials with 0.4 wt% SHMP content could undergo large strains of 30% and achieved a resilience ratio of 81.69% under the 30th compression cycle. Moreover, after heat treatment at 800 °C, SiO2 fibrous porous materials also maintained good elasticity with a resilience ratio of more than 80%. [ABSTRACT FROM AUTHOR]

Published
2022
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72. Impacts of soft soil compaction and groundwater extraction on subsidence in the Yellow River Delta.

Author

Zhang, Yi, Huang, Haijun, Liu, Yanxia, Bi, Haibo, Zhang, Zehua, Wang, Kuifeng, and Yan, Liwen

Subjects
SOIL compaction, LAND subsidence, SOIL mechanics, SOIL consolidation, GROUNDWATER, SOIL depth
Abstract

Recently, many of the world's major river deltas have been sinking, making them increasingly vulnerable to floods and storm surges, salinization and permanent inundation. For the Yellow River delta, annual subsidence rates of several to dozens of centimeters have been reported in the past few years. The extraction of a considerable amount of groundwater due to continuous pumping is suggested as the main driver of the groundwater depression cone. Despite its scale and severity, methods to quantify subsidence are scarce. We introduce a soil mechanics approach to quantify subsidence due to the compaction of soft soil. The largest reduction in soft soil thickness, which is more than 2.6 m, occurred in the salt field area to the north of the Yellow River. Furthermore, by estimating the primary consolidation of soft soil, the subsidence caused by groundwater exploitation is quantified. In the coastal area of the delta, due to excessive exploitation of shallow underground brine resources, the maximum accumulated subsidence is as high as 2 m. Since the natural consolidation of these deltaic sediments has ended, if the current groundwater exploitation intensity is maintained, major subsidence disasters, such as subsidence depressions and ground fissures, will occur. [ABSTRACT FROM AUTHOR]

Published
2021
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73. Preliminary study for the stimulation effect of plant-based meals on pure culture Lactobacillus plantarum growth and acidification in milk fermentation

Author

Jiang Yuanzhi, Lu Wenwei, Hong Qing, Hao Zhang, Jianxin Zhao, Yan Liwen, Feng Hang, and Wei Chen

Subjects
Avena, Cultured Milk Products, Stimulation, law.invention, 03 medical and health sciences, Probiotic, law, Genetics, Animals, Food science, 030304 developmental biology, 0303 health sciences, biology, Inoculation, Chemistry, Plant Extracts, Probiotics, 0402 animal and dairy science, food and beverages, Plant based, Hordeum, 04 agricultural and veterinary sciences, Hydrogen-Ion Concentration, biology.organism_classification, Yogurt, 040201 dairy & animal science, Milk, Fermentation, Pure culture, Animal Science and Zoology, Titration, Lactobacillus plantarum, Food Science
Abstract

Fermented dairy products have been recognized as the best carriers for the administration of probiotics. Because one of the potential probiotic strains, Lactobacillus plantarum, has poor proteolytic ability and weak acidifying capacity in milk fermentation, the aim of this study was to preliminarily investigate the stimulation effect of plant-based meals on L. plantarum CCFM8661 growth in milk, and subsequently develop a yogurt or yogurt drinks containing probiotic strain L. plantarum CCFM8661. Milk supplemented with different concentrations (5 to 10%, wt/wt) of oat extract and malt extract, inoculated with 2.5 × 107 cfu/mL of L. plantarum CCFM8661, and then incubated at 35°C. The pH value, titration acidity, and viable cell counts during 48-h fermentation at 35°C and 25-d storage at 4°C, were determined at different intervals. The results showed that the promotion effects of oat extract and malt extract on L. plantarum CCFM8661 growth rate in milk were much stronger than almond, walnut, sweet corn, peanut, and soybean meals. In addition, the stimulation effect of oat extract was associated with its concentration, and was much stronger than that of malt extract. Furthermore, viable counts and titration acidity of yogurt were gradually increased in the oat extract group, whereas viable counts were gradually decreased and titration acidity were slightly increased in the malt extract group during the 25-d storage at 4°C.

Published
2019

98. Research on the numerical fitting method of the spiral surface cross-section

Author

Hu deji, Ma suchang, Tang shijun, Zhao Wei, and Yan liwen

Subjects
Cubic Hermite spline, Smoothing spline, Hermite spline, Mathematical optimization, Mathematical analysis, Curve fitting, Monotone cubic interpolation, Tangent vector, Spline interpolation, Thin plate spline, Mathematics
Abstract

The screw rod is widely used in the oil drilling, chemical industry, light industry and so on. Its machining accuracy affects directly the quality and efficiency of instruments. Thus a deep research on the machining process of the screw rod is urgently needed. The fitting method of the spiral surface cross-section is one of the key issues. It was proposed that cubic spline and parametric cubic spline interpolation function were taken to approximate the spiral surface cross-section by comparing different methods of curve fitting. Coefficients of them were derived, fitting equations were presented and examples were taken to verify the fitting results .At the same time, key issues on the skewness, tangent vectors of ends and so on were involved both in the process of cubic spline and in parametric cubic spline fittings. Corresponding fitting function can be chosen on the basis of foregone data points, so as to provide smooth curves to generate accurate tool path. (4 pages)

Published
2009

99. Size dependence of optical and mechanical properties of Si3N4 nanobelts controlled by flow rates.

Author

Dong, Shun, Hu, Ping, Zhang, Xinghong, Cheng, Yuan, Zhang, Dongyang, Yan, Liwen, and Chen, Guiqing

Abstract

Single-crystalline Si3N4 nanobelts (NBs) were successfully synthesized in a size-controlled manner using graphite, nanosilicon and nanosilica powders in N2 gas. The average width of Si3N4 NBs increased with an increase in the flow rate of N2 gas, with 264 nm at 50 ml min−1, 295 nm at 100 ml min−1 and 341 nm at 200 ml min−1. The room-temperature photoluminescence (PL) spectra showed that the synthesized α-Si3N4 nanobelts with three different sizes all had two strong emission peaks located in the yellow and red spectral range, which could be mainly attributed to the incorporation of a small amount of Al in the NBs, and the larger size could also lead to a slight red shift. The Young's modulus of Si3N4 NBs was measured with a hybrid scanning electron microscope/scanning probe microscope (SEM/SPM) system by means of the modulated nanoindentation method. The Young's modulus of Si3N4 NBs strongly depended on their size, decreasing from about 548.6 to 455.1 GPa, which can be explained by surface effects and defect-related effects arising due to their nanometer size. These findings provide a method to tailor the optical and mechanical properties of the NBs in a controlled manner over a wide range of Young's modulus values. [ABSTRACT FROM AUTHOR]

Published
2016
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