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The viscoelasticity, anisotropy and location-dependence of mechanical properties of rabbit iris investigated using uniaxial tensile tests

Li Tan, Qin Xiao, Liu Zhicheng, Zhang Haixia, Li Lin

Acta of Bioengineering and Biomechanics

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2023

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Vol. 25, no. 2

85--92

EN

Abnormal iris mechanical properties have been considered to be an important cause of pupillary-block and angle-closure glaucoma. In this research, viscoelasticity, anisotropy and location-dependence of mechanical properties of rabbit iris were investigated using uniaxial tensile test. Methods: Iris strips were taken along three directions: inner-circumferential direction (ICD), outer-circumferential direction (OCD) and radial direction (RD), respectively. Quasi-static tensile tests and stress–relaxation tests were applied on the iris strips. Then, the stress–stretch data was fitted with third order Ogden model; the stress–relaxation data was fitted with the third order Prony series model. Through comparing the tangent modulus and relaxation limit of the strips from different directions and locations, the viscoelasticity, anisotropy and location-dependence of mechanical properties of rabbit iris were explored. Results: The tangent moduli of iris at the stretch of 1.05 along ICD, OCD, and RD were 3.2 ± 1.4 kPa, 4.2 ± 2.6 kPa, 1.5 ± 0.8 kPa, respectively. Iris strips in ICD and OCD were found to have almost the same stress–relaxation behavior, and both relaxed slower than iris strips in RD. Conclusions: The mechanical properties of the iris were typically nonlinear, viscoelastic, anisotropic and location-dependent. The stress growth rate of the circumferential direction iris strip is significantly lower than that of RD and the stress–relaxation rate is significantly higher than that of the RD. That is, the iris is more prone to deformation in RD and the stress–retention ability after deformation in RD is weak, which is consistent with the fact that the iris bombe more likely happens in RD in vivo. The results of this study may also help us to establish a more accurate finite element model to simulate the flow field of humor aqueous and find the key factor of pupillary-block.

2

RFID tag group recognition based on motion blur estimation and YOLOv2 improved by Gaussian algorithm

Li Lin, Yu Xiao-Lei, Liu Zhen-Lu, Zhao Zhi-Min, Zhang Ke, Zhou Shan-Hao

Metrology and Measurement Systems

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2022

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Vol. 29, nr 1

53--74

EN

Effective recognition of tags in the dynamic measurement system would significantly improve the reading performance of the tag group, but the blurred outline and appearance of tag images captured in motion seriously limit the effectiveness of the existing tag group recognition. Thus, this paper proposes passive tag group recognition in the dynamic environment based on motion blur estimation and improved YOLOv2. Firstly, blur angles are estimated with a Gabor filter, and blur lengths are estimated through nonlinear modelling of a Generalized Regression Neural Network (GRNN). Secondly, tag recognition based on YOLOv2 improved by a Gaussian algorithm is proposed. The features of the tag group are analyzed by the Gaussian algorithm, the region of interest of the dynamic tag is effectively framed, and the tag foreground is extracted; Secondly, the data set of tag groups are trained by the end-to-end YOLOv2 algorithm for secondary screening and recognition, and finally the specific locations of tags are framed to meet the effective identification of tag groups in different scenes. A considerable number of experiments illustrate that the fusion algorithm can significantly improve recognition accuracy. Combined with the reading distance, the research presented in this paper can more accurately optimize the three-dimensional structure of the tag group, improve the reading performance of the tag group, and avoid the interference and collision of tags in the communication channel. Compared with the previous template matching algorithm, the tag group recognition ability put forward in this paper is improved by at least 13.9%, and its reading performance is improved by at least 6.2% as shown in many experiments.

3

Synthesis of a magnetic ionic liquid ([C12mim]FeCl4) and its interactions with low-rank coal

Li Zhihao, Liu Mingpu, Lin Mengyu, Ma Chuandong, He Meng, Wang Qingbiao, Yu Hao, Li Lin, You Xiaofang

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 3

566--578

EN

he large number of oxygen-containing functional groups present on the surface of low-grade coal contribute to its strong hydrophilic properties and rendering coal beneficiation by flotation challenging. In this study, a magnetic ionic liquid (IL), [C12mim]FeCl4, was developed as a green medium to treat low-rank coal. Notably, the IL can be recovered using a magnetic field. The interactions between the low-rank coal and the IL were analyzed, and the structure and properties of [C12mim]FeCl4 were characterized using Raman spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, and vibrating-sample magnetometry. Moreover, the effects of the newly prepared IL on the wetting properties of low-rank coal were studied using water contact angle measurements. The contact angle of the coal sample treated with the IL increased initially but decreased with subsequent increase in treatment time, indicating a change in coal wettability with time. The results from FT-IR analysis show that the changes in contact angles may be attributed to the changes to the oxygen-containing functional groups at the coal surface upon interaction with the IL, where the content of oxygen-containing functional groups in the treated coal sample initially decreased but subsequently increased with increase in treatment time. X-ray photoelectron spectroscopy analysis confirmed these results. Thus, it can be concluded that [C12mim]FeCl4 initially destroys the oxygen-containing functional groups at the coal surface, resulting in an increase in the water-coal contact angle but subsequently promoting oxidation of the coal surface, hence causing a reduction in the contact angle.

4

Effect of the degree of polymerization of nonylphenol polyoxyethylene ether on the dewatering of low-rank coal

Li Lin, He Meng, Liu Mingpu, Lin Mengyu, Hu Shanpei, Yu Hao, Wang Qingbiao, You Xiaofang

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 4

723--736

EN

In this study, we investigated the effect of the hydrophilic ethylene oxide chain lengths (i.e., degree of polymerization) of nonylphenol polyoxyethylene ether (NPEO-x, x = 8, 10, and 12) on the dewatering of low-rank coal slime through dewatering and adsorption experiments and X-ray photoelectron spectroscopy (XPS) measurements. The dewatering experiments showed that the adsorption of NPEO changed the water content of the low-rank coal slime: NPEO-8 achieved the best effect, followed, in decreasing order, by NPEO-10 and NPEO-12. Adsorption experiments revealed that the adsorption isotherms of NPEO-x on the low-rank coal surface conform with the Langmuir model, and its adsorption kinetics follow the pseudo-second-order kinetic equation. Furthermore, the adsorption is a spontaneous process and controlled by both intraparticle diffusion and liquid film diffusion. The XPS results showed that the adsorption of NPEO-x decreased the content of oxygencontaining groups and, thus, improved the hydrophobicity of the low-rank coal surface. Further, the use of NPEO-x with a low degree of polymerization (x = 8) improves the hydrophobicity of the coal surface and decreases the water content of low-rank coal slime.

5

Design and computation of a lightning protection system in an urban 110 kV substation

Taha Mohammed Ibrahim, Li Lin, Wang Ping

Archives of Electrical Engineering

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2020

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Vol. 69, nr 3

723--738

EN

A lightning protection system (LPS) of an urban 110 kV substation is designed and analysed according to NFPA 780 and IEC 62305-3 standards. The analysis of the LPS is established on the value of risk assessment. The total area of the plant is described by one soil layer with uniform resistivity. This study aims to improve the understanding of an unexpected manner of the grounding system beneath lightning currents by clarifying the basic concepts of the lightning protection level and the new design procedure in this paper was clarified according to NFPA-780 level 1 for a lightning protection system. The program is integrated with the CDEGS software, which provides effective geometrical modeling with object and result visualization. Furthermore, module and automated fast Fourier transform (FFT) is implemented in this study to simulate electromagnetic fields in the time and frequency domains. These current values are compared to the desired protection levels within the standards. The study results show that for the improved protection of the system against lightning, the total power grid must be considered as a source of improvement for studying shielding influence and the protection levels provided inside this substation.

6

Structure and dynamics of water adsorbed on the lignite surface: Molecular dynamics simulation

You Xiaofang, He Meng, Cao Xiaoqiang, Lyu Xianjun, Li Lin

Physicochemical Problems of Mineral Processing

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2019

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Vol. 55, iss. 1

10--20

EN

The effects of oxygen-containing functional groups on the structure and dynamic properties of water molecules near a lignite surface were investigated through molecular dynamics (MD) simulations. Because of its complex composition and structure, a graphite surface containing hydroxyl, carboxyl, and carbonyl groups was used to represent the lignite surface model. According to X-ray photoelectron spectroscopic (XPS) results, the composing proportion of hydroxyl, carbonyl and carboxyl is 21:13:6. The density profiles of oxygen and hydrogen atoms indicate that the brown coal surface characteristics influence the structural and dynamic properties of water molecules. The interfacial water is much more ordered than bulk water. The results of the radial distribution functions, mean square displacements, and local self-diffusion coefficients for the water molecules in the vicinity of three oxygen-containing functional groups confirmed that carboxyl groups are the preferential adsorption sites.

7

Adsorption behavior and XPS analysis of nonylphenol ethoxylate on low rank coal

You Xiaofang, Ma Chuandong, Li Zhihao, Lyu Xianjun, Li Lin

Physicochemical Problems of Mineral Processing

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2019

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Vol. 55, iss. 3

721--731

EN

In this work, low rank coal was used for the removal of nonylphenol ethoxylate with fifteen ethylene oxide groups (NPEO15) from aqueous solutions at different contact times, temperatures, and initial adsorbent concentrations. The adsorption isotherms showed good fit with the Langmuir equation. Maximum adsorption capacities calculated at 308, 318, and 328 K were 23.64, 29.41, and 35.71 mg g–1, respectively. The changes in the free energy of adsorption (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) were calculated in order to predict the nature of adsorption. The results of the thermodynamic analysis indicated that a spontaneous process took place, driven synergistically by both enthalpy and entropy. The adsorption kinetics of NPEO15 were consistent with a pseudo-second order reaction model. XPS results showed that the oxygen functional groups on the low rank coal surface were significantly covered by NPEO15. Furthermore, while the content of C–C/C–H functional groups increased significantly, that of C–O functional groups decreased after absorption. These results clearly indicate that low rank coal is more hydrophobic and displays better floatability.