Stress Evolution Law and Failure Characteristics of Mining Floor Rock Mass above Confined Water

Shiliang Liu,Weitao Liu,Jianjun Shen 대한토목학회 2017 KSCE Journal of Civil Engineering Vol.21 No.7

The discussion of stress evolution law and failure characteristics of rock mass in mining floor above confined water is the key to control the floor water inrush in deep mining. Based on analyzing the strike support pressure of working face, the mechanical model of coal floor above the confined water was established. Then, vertical, horizontal and shear stress distribution maps and the failure range morphological map of mining floor were calculated based on data processing software Origin. Then, with the similar simulation test bed for water inrush from coal seam floor, the fluid solid coupling simulation material was selected, and the stress evolution law and failure characteristics of coal seam mining floor were improved. The results showed that the vertical stress contour is a “semi-elliptical” shape distribution and the greater the floor depth, the smaller the affected degree, but the influenced range increased. The higher shear stress zone occurred in the vicinity of working face coal wall. The failure range morphological map of mining floor was approximately a spoon shape and maximum failure depth was 14.0 m based on the mechanical theory. The maximum failure depth of the floor was 13.4 m based on the similar simulation experiment. So, the experimental results are in agreement with the theoretical results. The results in this paper can provide theory basis for safety mining above confined water.

Preparation and characterization of novel polyethylene/carbon nanotubes nanocomposites with core–shell structure

Zhi Liu,Qigu Huang,Mengshan Yu,Jing Wang,Fengjiao Li,Lu Cheng,Jiangping Guo,Yang Zhou,Baichun Zhu,Jianjun Yi,Yunfang Liu,Wantai Yang 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.4

Preparation of novel polyethylene/carbon nanotubes (CNTs) nanocomposites with core–shell structure was presented. The method involved in situ ethylene polymerization in which nanotube surface was treated with Grignard Agent, followed by reacting with active transition metal compound, TiCl4. The multiwalled carbon nanotubes (MWCNTs) supported catalysts polymerize ethylene to form polymer nanocomposite. MWCNTs were homogeneously dispersed within polymer matrix, and as expected, the resultant nanocomposites featured core–shell structure which was confirmed by HRTEM. For the nanocomposite, the microscopic examination of the cryogenically fractured surface not only ensured a good distribution of carbon nano-particles in the PE matrix but also revealed the ductile-like fracture. The Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were employed for the study of covalent sidewall functionalization and chemical bonding environment of MWCNTs, also indicated effective immobilization of titanium catalyst on the MWCNTs surface. The crystalline properties, dielectric property and thermal stability of the nanocomposites were determined by WAXD, impedance analyzer and TGA. The dielectric result showed a slight decline of the dielectric constant of the nanocomposites with increase of the polymerization time, and lower dielectric loss was also observed.

Synthesis of (co-)polyethylene with broad molecular weight distribution by the heterogenous Ziegler–Natta catalysts via one-pot strategy

Zhi Liu,Xinli Zhang,Haibing Huang,Jianjun Yi,Wei Liu,Weijiao Liu,Hongpeng Zhen,Kejing Gao,Mingge Zhang,Wantai Yang,Qigu Huang 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.6

A new method was presented for preparing (co-)polyethylene with broad molecular weight distribution (MWD) and high molecular weight employed by the novel heterogeneous Ziegler–Natta catalysts via one-pot strategy. The preparation of these catalysts involved the introduction of alkoxy silane compounds as electron donors. The influences of the electron donors structure, as well as polymerization conditions such as temperature, molar ratio of Al/Ti, ethylene pressure and the concentration of 1-hexene in feed on the polymerization performance for ethylene (co-)polymerization, were investigated. The morphology of the catalyst particles was characterized by SEM and Ti content of these catalysts was characterized by ICP. The GPC results showed that the obtained homopolyethylene and ethylene/1-hexene copolymer had the widest molecular weight distribution up to ca 50 when diethoxy-isopropoxy-(t–butoxy)-silane (ED3) was used as internal electron donor. The 13C NMR and FT-IR analysis indicated that these catalysts efficiently catalyzed the copolymerization of ethylene with 1-hexene.

Chinese Society of Allergy and Chinese Society of Otorhinolaryngology-Head and Neck Surgery Guideline for Chronic Rhinosinusitis

Zheng Liu,Jianjun Chen,Lei Cheng,Huabin Li,Shixi Liu,Hongfei Lou,Jianbo Shi,Ying Sun,Dehui Wang,Chengshuo Wang,Xiangdong Wang,Yongxiang Wei,Weiping Wen,Pingchang Yang,Qintai Yang,Gehua Zhang,Yuan Zhan 대한천식알레르기학회 2020 Allergy, Asthma & Immunology Research Vol.12 No.2

The current document is based on a consensus reached by a panel of experts from the Chinese Society of Allergy and the Chinese Society of Otorhinolaryngology-Head and Neck Surgery, Rhinology Group. Chronic rhinosinusitis (CRS) affects approximately 8% of Chinese adults. The inflammatory and remodeling mechanisms of CRS in the Chinese population differ from those observed in the populations of European descent. Recently, precision medicine has been used to treat inflammation by targeting key biomarkers that are involved in the process. However, there are no CRS guidelines or a consensus available from China that can be shared with the international academia. The guidelines presented in this paper cover the epidemiology, economic burden, genetics and epigenetics, mechanisms, phenotypes and endotypes, diagnosis and differential diagnosis, management, and the current status of CRS in China. These guidelines—with a focus on China—will improve the abilities of clinical and medical staff during the treatment of CRS. Additionally, they will help international agencies in improving the verification of CRS endotypes, mapping of eosinophilic shifts, the identification of suitable biomarkers for endotyping, and predicting responses to therapies. In conclusion, these guidelines will help select therapies, such as pharmacotherapy, surgical approaches and innovative biotherapeutics, which are tailored to each of the individual CRS endotypes.

Covalent Immobilization of Arginine onto Polyacrylonitrile-Based Membrane for the Effective Separation of Oil/Water Emulsion

Xiang Shen,Peng Liu,Jiao Xu,Teng Liu,Jianjun Liu,Xianfu Shen,Shubiao Xia,Fan Wang 한국고분자학회 2018 Macromolecular Research Vol.26 No.13

Membrane technology has been accepted as a very effective approach to purify oily wastewater. However, the serious membrane fouling induced by the adsorption of oily foulants significantly hinders the development of membrane technology in treating oily wastewater. To improve the anti-fouling property and oil/ water separation efficiency of membrane, this work reports on the covalent immobilization of short-chain arginine (Arg) molecules onto polyacrylonitrile/polyacrylonitrile- co-poly(glycidyl methacrylate) (PAN/PAN-co-PGMA) blend membrane surface via a ring-opening reaction between epoxy groups and amine groups. It was found that the covalent immobilization of Arg molecules effectively increased the surface hydrophilicity of the membrane, resulting in a significant decrease of the interaction force between the foulants and the membrane surface. This typical characteristic was revealed by the pure water contact angle and the force-extension curve measurements. The Arg-immobilized membranes exhibited much higher separation efficiency against oil/water emulsions than the pristine PAN and PAN/PAN-co-PGMA membranes. Especially when the grafting amount of Arg was 157.3 μg/cm2, the oil rejection ratio of an Arg-immobilized membrane was as high as 99.2%. In addition, the flux recovery ratio of the membrane still reached 88.8%, even after two cycle filtrations of pure water and oil/water emulsion. These results indicated that the Arg-immobilized membrane may have practical applications for oil/water emulsion separation.

Trichloroethylene injures rat liver and elevates the level of peroxisomal bifunctional enzyme (Ehhadh)

Nuanyuan Luo,Qunqun Chang,Xiaohu Ren,Peiwu Huang,Wei Liu,Li Zhou,Yungang Liu,Jianjun Liu 대한독성 유전단백체 학회 2020 Molecular & cellular toxicology Vol.16 No.3

Background Trichloroethylene (TCE) is a common industrial solvent and an occupational toxicant. TCE exposure can cause severe hepatotoxicity, but its mode of action is poorly understood. Many studies have shown TCE-induced liver damage in mice, while few have examined the effects of TCE in rats. Objective To explore the effects of TCE in Sprague–Dawley (SD) rats and the potential mechanisms in TCE-induced hepatocytotoxicity. Results The liver index and activities of liver damage marker enzymes (ALT, AST and ALP) in rat serum were elevated along with the increase in TCE dose, while the levels of total proteins and albumin in serum were reduced. The results suggest that TCE is hepatotoxic in rats. 2D-DIGE electrophoresis showed that the levels of 66 liver proteins in TCE-treated rats were abnormally altered (39 up-regulated and 27 down-regulated). In these proteins, six enzymes were related to liver damage and carcinogenesis as indicated by bioinformatics analysis, and Western blot analysis confirmed the alterations of three of them, i.e., aldehyde dehydrogenase 2 (Aldh2), glutathione S-transferase Mu 1 (Gstm1) and peroxisomal bifunctional enzyme (PBE, also named as Ehhadh). PBE was the only protein elevated in a dose dependent manner. Whether PBE can be a biomarker of TCE hepatotoxicity needs to be further studied. Conclusion These findings indicate that TCE induces liver injury in rats.

An Improved Attention-based Bidirectional LSTM Model for Cyanobacterial Bloom Prediction

Jianjun Ni,Ruping Liu,Guangyi Tang,Yingjuan Xie 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.10

Cyanobacterial blooms are one of the most serious water pollution problems for freshwater lakes. The treatment of blooms requires a lot of material and financial resources, so an early accurate prediction of cyanobacterial blooms is a very important way to deal with the outbreak of them. But it is challenging to predict the cyanobacterial blooms due to the uncertainty and complexity of their growth process. To deal with this problem, an improved attention-based bidirectional long short-term memory (LSTM) model is proposed in this paper, to make multistep predictions of chlorophyll-a concentration, which is a recognized characterization of algae activity. Firstly, the convolutional neural network (CNN) is used to extract data features and spatiotemporal correlation. Secondly, the bidirectional LSTM network (BiLSTM) is used to predict the concentration of chlorophyll-a based on the extracted features. Finally, the attention mechanism is used to calculate the weights for the characteristic factors that affect the chlorophyll-a concentration. At last, some experiments are carried out based on the real monitoring data of a platform in the Taihu Lake area. Compared with the prediction results of the other four state-of-the-art deep learning methods, the results show that the proposed method in this paper has the highest prediction accuracy.

Role of Intermetallics on Fatigue Behaviuor of Stainless Steel Adhered by Sn

Jianjun Guan,Yan Zhao,Feng Liu,Jie Zhao 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.6

The fatigue property of 304 stainless steel (SS) adhered by Fe-Sn intermetallics was investigated. The microstructure of crack nucleation and crack propagation was observed, and the influence of Fe-Sn intermetallics on fatigue failure was analyzed. Fatigue tests at stress ratio of R = -1 were performed using a sine waveform at 20 Hz frequency under load control. In addition, the morphology and microfractography of the Fe-Sn intermetallics were examined under a scanning electron microscope. Results demonstrated that the adherence of the interfacial (Fe, Cr)Sn2 layer reduced the fatigue life of the 304 SS substrates. The fatigue cracks also exhibited the intergranular fracture characteristics of the intermetallics. The brittle (Fe, Cr)Sn2 intermetallics were apt to fatigue crack nucleation. The interfacial metallurgical bonding, which was caused by diffusion reaction between Fe and Sn atoms, led to crack propagation into the SS substrate.

Nonlinear wind-induced instability of orthotropic plane membrane structures

Liu, Changjiang,Ji, Feng,Zheng, Zhoulian,Wu, Yuyou,Guo, Jianjun Techno-Press 2017 Wind and Structures, An International Journal (WAS Vol.25 No.5

The nonlinear aerodynamic instability of a tensioned plane orthotropic membrane structure is theoretically investigated in this paper. The interaction governing equation of wind-structure coupling is established by the Von $K\acute{a}rm\acute{a}n's$ large amplitude theory and the D'Alembert's principle. The aerodynamic force is determined by the potential flow theory of fluid mechanics and the thin airfoil theory of aerodynamics. Then the interaction governing equation is transformed into a second order nonlinear differential equation with constant coefficients by the Bubnov-Galerkin method. The critical wind velocity is obtained by judging the stability of the second order nonlinear differential equation. From the analysis of examples, we can conclude that it's of great significance to consider the orthotropy and geometrical nonlinearity to prevent the aerodynamic instability of plane membrane structures; we should comprehensively consider the effects of various factors on the design of plane membrane structures; and the formula of critical wind velocity obtained in this paper provides a more accurate theoretical solution for the aerodynamic stability of the plane membrane structures than the previous studies.

The existence and multiplicity of solutions of three-pointp-Laplacian boundary value problems with one-sided Nagumocondition

Jianjun Zhang,Wenbin Liu,Jinbo Ni,Taiyong Chen 한국전산응용수학회 2007 Journal of applied mathematics & informatics Vol.24 No.1