Failure Mechanism of Giant-Thick Strata Characterized by Weak Cementation Based on Superimposed Similar Material Simulation

Guojian Zhang,Guangli Guo,Yaqiang Gong,Anliang Xiao,Tonglong Zhao,Huaizhan Li 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.8

Deep mining puts forward higher requirements for the existing similar material simulation methods and monitoring techniques. The idea of superimposed similar material simulation is proposed to study the motion mechanism of high-stand and giant-thickness weak cementation sandstone, and its motion law is observed by the new method of single-binocular close-range photogrammetry, and verified by numerical simulation method. The results show that: first, the measurement accuracy of single close-range photogrammetry reaches the sub-millimeter level, with its medium errors of 0.18 mm and 0.17 mm in left and right camera respectively. Second, during the damage process of the thick weak cementation strata, the secondary equilibrium structure and regenerative equilibrium structure are formed, causing the destruction mode to go through four stages of ‘arch shell-beam-arch shell-step’ type damage. After the ‘arch shell-beam’ type destruction of the thick Zhidan group sandstone, its movement process disappears in the temporal correlation and shows the characteristics of the surface subsiding immediately after mining. Last, the surface subsidence develops with the saltation, and there is a quadratic polynomial function between the surface subsidence coefficient and the width-depth ratio. The above results can be used to guide the safety mining under the giant-thick weak cementation overburden.

Monitoring Sluice Health in Vibration by Monocular Digital Photography and a Measurement Robot

Guojian Zhang,Chengxin Yu,Guangli Guo,Long Li,Yongqian Zhao,Huaizhan Li,Yaqiang Gong 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.6

This study uses monocular digital photography and a measurement robot (MDP&MR) to monitor the sluice vibration deformation in the gate lift test and in the sluicing test. The photographing scale transformation and time baseline parallax (PST-TBP) method is proposed in the field of monocular digital photography. Results show that the PST-TBP method improves measurement accuracy slightly. Measurement accuracies on the reference plane were 0.62 pixels (0.40 mm), 0.76 pixels (0.49 mm), and 1.10 pixels (0.71 mm) in the X, Z, and comprehensive-directions, respectively. The PST-TBP method overcomes the limitation that the photographing direction must be perpendicular to the sluice plane when monocular digital photography is used to monitor the sluice. MDP&MR proves an effective method in monitoring the sluice vibration deformation as MDP can be used to monitor the trend of the sluice vibration deformation and the MR allows high-accuracy monitoring of the short periodic deformation of the sluice. They have complementary advantages to achieve better results. Thus, MDP&MR can provide a new way to assess sluice health in vibration.

Study on the thermoelectric properties of porous Bi-Te films deposited using thermal evaporation on AAO template

Shiying Liu,GUOJIAN LI,Mingdi Lan,Yongjun Piao,Yanan Zhang,QIANG WANG 한국물리학회 2020 Current Applied Physics Vol.20 No.3

The application of thermoelectric films is limited to retain the temperature gradient. In this study, the Bi-Te films are deposited on the AAO template with a pore size of 100 nm using thermal evaporation. The results show that the conductive types of the Bi-Te film are tuned by source temperature. The power factor of the p-type porous film decreases 36% by comparing to that of the p-type nonporous film (1020 μW/mK2 at 250 °C). Meanwhile, the temperature difference in the porous device is maintained and is approximately 5.0 °C. Thus, the maximum output power is achieved in the porous device (about 25 pW), which is 5 times higher than that of the nonporous device. This provides a method to improve the conversion efficiency of thermoelectric film device by maintaining the temperature difference by using porous structure.

Diffusion mechanism of deep shale gas and its carbon isotope fractionation: a combined simulated and mathematical analysis

Yu Zou,Guojian Wang,Cheng Tao,Rui Zhou,Shangqing Zhang,Dongna Liu,Xiaohui Lin,Xuying Zheng 한국지질과학협의회 2023 Geosciences Journal Vol.27 No.3

Unlike the release pressure process in shale gas exploitation, in this study, the concentration diffusion process is deeply discussed under constant temperature-pressure conditions, which aims to evaluate the preservation conditions of shale gas reservoirs in combination with isotopic fractionation characteristics. The isobaric diffusion experiment emphasized that decreasing pressure can lead to enhanced diffusion and isotope fractionation. The established mathematical model not only confirms the results of the simulating experiment, but also suggests that the contributions of Fick, Knudsen and surface diffusion to the migration of methane (including 12CH4 and 13CH4) vary in the geological evolution of shale reservoirs, which are mainly controlled by the pore system and gas pressure. Based on the analysis of specific samples of Longmaxi shale (r = 11.7 nm) and Niutitang shale (r = 1.3 nm), we propose that: 1) high pressure condition (> 20 MPa) can significantly limit Knudsen diffusion, which is the reason for reducing the total diffusion coefficient (DTotal) and isotope fractionation, while low pressure (< 10 MPa) and small pore radius (ca. 1 nm) can strengthen the fractionation; 2) pore connectivity and heterogeneity can lead to an order of magnitude change in DTotal, while the influence of temperature is relatively small. According to the mathematical model, it can be expected that enhanced dissipation intensity and isotope fractionation of shale gas may occur in the process of basin uplift and pressure relief, which can potentially be used for the evaluation of reservoir preservation.

Quantitative Characterization Method for Rock Surface Roughness with Different Scale Fluctuation

Yuhang Guo,Chuanqing Zhang,Hang Xiang,Guojian Cui,Fanzhen Meng,Hui Zhou 대한토목학회 2022 KSCE Journal of Civil Engineering Vol.26 No.4

Quantitative characterization of the surface roughness plays a vital role in the field of rock mechanics. The objectives of this study were to propose a new index that can describe the various morphological characteristics with different scale fluctuation. The power spectral density (PSD) parameters and conventional statistical parameters were used to analyze the roughness of meso-scale grind surfaces, intermediate-scale synthesis surfaces, and macro-scale shear surfaces. The results showed that the PSD parameters (slope k, intercept b, spectral moment λ0, and spectral shape parameters ω1 and ω2) and conventional statistical parameters(RMS and Z2) have evident uniqueness and uniformity in characterizing the roughness with different scale fluctuation. It is necessary to appropriately use the correct parameters for classifying and quantifying the roughness. For this purpose, a new characterization index SLAwas proposed based on the spectral shape parameter ω1, spectral moment λ0, slope k, and angle fractal index C.

Scalded Skin of Rat Treated by Using Fibrin Glue Combined with Allogeneic Bone Marrow Mesenchymal Stem Cells

( Yadong Yang ),( Wenyuan Zhang ),( Ying Li ),( Guojian Fang ),( Keji Zhang ) 대한피부과학회 2014 Annals of Dermatology Vol.26 No.3

Background: It is difficult to achieve satisfactory results with the traditional treatment of large-area skin defects and deep burns. Objective: To test the treatment effect of an active dressing film made of a mixture of fibrin glue and bone marrow mesenchymal stem cells (BMSCs) for repairing burn wounds on the skin of rats. Methods: Two scald wounds were made on the back of each rat. A total of 30 scald wounds were randomly divided into 3 groups, with 10 wounds in each group. In the experimental treatment group, the scald wounds were covered with the fibrin glue and BMSC mixture. The wounds of the experimental control group were covered with fibrin glue only. No intervention was administered to the blank control group. Thirty days after treatment, pathological sections were cut from the scalded local tissues of all rats from the 3 groups and observed with a microscope. Results: The speed of scald wound healing in the experimental treatment group was faster than the other 2 groups. In the experimental treatment group, histopathological analysis revealed that the sebaceous glands showed obviously proliferous at the edge of the new tissue and gradually extended to the deep dermal layer of the new tissue. Conclusion: BMSCs may have an active role in promoting skin tissue repair and generating skin appendages. Allogeneic BMSCs mixed with fibrin glue can contribute to the quick formation of a film-like gel over the scald wounds, which might be of significance for emergency treatment and skin-grafting operations. (Ann Dermatol 26(3) 289∼295, 2014)

Dynamics of fungal community during silage fermentation of elephant grass (Pennisetum purpureum) produced in northern Vietnam

Viet Ha Vu,Xiyang Li,Mengyuan Wang,Rongmei Liu,Guojian Zhang,Wei Liu,Baixue Xia,Qun Sun 아세아·태평양축산학회 2019 Animal Bioscience Vol.32 No.7

Objective: This study aimed to gain deeper insights into the dynamic changes in spoilage fungi populations during fermentation and the influence of traditional additives on silage quality. Methods: Elephant grass (Pennisetum purpureum) was prepared without any additive (control), and with the addition of 0.5% salt, and 0.5% salt–0.2% sugar mixture. The fungal community was then determined using a classic culturing method and high-throughput sequencing at 0, 5, 15, and 60 days after ensiling. Results: The results showed that the fungal community of elephant grass silage varied significantly between the natural fermentation without any additive and the two additive groups. The diversity and relative abundance of spoilage molds in the control group were much higher than those in the two treatment groups (p<0.05). Three species of yeasts (Candida sp., Pichia sp., Trichosporon sp.) and four spoilage molds (Fusarium sp., Aspergillus sp., Muco sp. and Penicillin sp.) were the predominant fungi in elephant grass during natural fermentation from 0 to 60 days, which were found to be significantly decreased in salt and sugar additive groups (p<0.05). Meanwhile, the diversity and relative abundance of undesirable molds in the 0.5%-salt additive group were the lowest among all groups. Conclusion: Adding salt and sugar, particularly 0.5% salt, is a promising effective approach to reduce the amount of undesirable fungi thus, improving the silage quality of elephant grass in northern Vietnam.