Modeling of time-varying stress in concrete under axial loading and sulfate attack

Guang-Ji Yin,Xiao-Bao Zuo,Yu-Juan Tang,Olawale Ayinde,Dong-Nan Ding 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.19 No.2

This paper has numerically investigated the changes of loading-induced stress in concrete with the corrosion time in the sulfate-containing environment. Firstly, based on Fick’s law and reaction kinetics, a diffusion-reaction equation of sulfate ion in concrete is proposed, and it is numerically solved to obtain the spatial and temporal distribution of sulfate ion concentration in concrete by the finite difference method. Secondly, by fitting the existed experimental data of concrete in sodium sulfate solutions, the chemical damage of concrete associated with sulfate ion concentration and corrosion time is quantitatively presented. Thirdly, depending on the plastic-damage mechanics, while considering the influence of sulfate attack on concrete properties, a simplified chemo-mechanical damage model, with stress-based plasticity and strain-driven damage, for concrete under axial loading and sulfate attack is determined by introducing the chemical damage degree. Finally, an axially compressed concrete prism immersed into the sodium sulfate solution is regarded as an object to investigate the time-varying stress in concrete subjected to the couplings of axial loading and sulfate attack.

Colonic Hypersensitivity and Sensitization of Voltage-gated Sodium Channels in Primary Sensory Neurons in Rats with Diabetes

( Ji Hu ),( Zhen Yuan Song ),( Hong Hong Zhang ),( Xin Qin ),( Shufen Hu ),( Xinghong Jiang ),( Guang Yin Xu ) 대한소화기기능성질환·운동학회 2016 Journal of Neurogastroenterology and Motility (JNM Vol.22 No.1

Background/Aims Patients with long-standing diabetes often demonstrate intestinal dysfunction and abdominal pain. However, the pathophysiology of abdominal pain in diabetic patients remains elusive. The purpose of study was to determine roles of voltage-gated sodium channels in dorsal root ganglion (DRG) in colonic hypersensitivity of rats with diabetes. Methods Diabetic models were induced by a single intraperitoneal injection of streptozotocin (STZ; 65 mg/kg) in adult female rats, while the control rats received citrate buffer only. Behavioral responses to colorectal distention were used to determine colonic sensitivity in rats. Colon projection DRG neurons labeled with DiI were acutely dissociated for measuring excitability and sodium channel currents by whole-cell patch clamp recordings. Western blot analysis was employed to measure the expression of NaV1.7 and NaV1.8 of colon DRGs. Results STZ injection produced a significantly lower distention threshold than control rats in responding to colorectal distention. STZ injection also depolarized the resting membrane potentials, hyperpolarized action potential threshold, decreased rheobase and increased frequency of action potentials evoked by 2 and 3 times rheobase and ramp current stimulation. Furthermore, STZ injection enhanced neuronal sodium current densities of DRG neurons innervating the colon. STZ injection also led to a significant upregulation of NaV1.7 and NaV1.8 expression in colon DRGs compared with age and sex-matched control rats. Conclusions Our results suggest that enhanced neuronal excitability following STZ injection, which may be mediated by upregulation of NaV1.7 and NaV1.8 expression in DRGs, may play an important role in colonic hypersensitivity in rats with diabetes. (J Neurogastroenterol Motil 2016;22:129-140)

Preparation and properties of ZrB2-YAG-Al2O3 ceramics

Jie-Guang Song,Gang-Chang Ji,Shi-Bin Li,Yang-Liang Li,Da-Ming Du,Lian-Meng Zhang,Yin-Yan Ju 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.4

ZrB2, YAG and Al2O3 are widely applied because of some excellent properties, but ZrB2 is easily oxidized in high-temperature air. To achieve better properties in ZrB2 ceramics, high-density ZrB2-YAG-Al2O3 ceramics were prepared. Below 1000℃, the shrinkage of ZrB2-YAG-Al2O3 ceramics is less than that of ZrB2-YAG ceramics. From 1000℃ to 1600℃, the second largest shrinkage occurs. Above 1600℃, the shrinkage of ZrB2-YAG-Al2O3 ceramics is more than that of ZrB2-YAG ceramics. The fracture toughness of sintered ceramics from coated raw materials is higher than that of sintered ceramics with mixed raw materials with the same phases and phase content, the fracture toughness of ZrB2-YAG-Al2O3 ceramics is higher than that of ZrB2-YAG ceramics with the same raw materials. The weight gain of all types of ceramics is increased with all increase in the oxidation temperature, the weight gain of ceramics is reduced with all increase in the YAG-Al2O3 content and Al2O3 proportion, especially above 1500℃. ZrB2, YAG and Al2O3 are widely applied because of some excellent properties, but ZrB2 is easily oxidized in high-temperature air. To achieve better properties in ZrB2 ceramics, high-density ZrB2-YAG-Al2O3 ceramics were prepared. Below 1000℃, the shrinkage of ZrB2-YAG-Al2O3 ceramics is less than that of ZrB2-YAG ceramics. From 1000℃ to 1600℃, the second largest shrinkage occurs. Above 1600℃, the shrinkage of ZrB2-YAG-Al2O3 ceramics is more than that of ZrB2-YAG ceramics. The fracture toughness of sintered ceramics from coated raw materials is higher than that of sintered ceramics with mixed raw materials with the same phases and phase content, the fracture toughness of ZrB2-YAG-Al2O3 ceramics is higher than that of ZrB2-YAG ceramics with the same raw materials. The weight gain of all types of ceramics is increased with all increase in the oxidation temperature, the weight gain of ceramics is reduced with all increase in the YAG-Al2O3 content and Al2O3 proportion, especially above 1500℃.

Effect of the sintering technology on the properties of fired brick from quartz sands

Jie-Guang Song,Fang Wang,Xiao-Bo Bai,Da-Ming Du,Yin-Yan Ju,Ming-Han Xu,Gang-Chang Ji 한양대학교 세라믹연구소 2011 Journal of Ceramic Processing Research Vol.12 No.4

River sands as low grade natural raw materials are used to prepare the fired brick to replace clay fired bricks, which aims to save land resources and use low grade natural resources to realize high cost performance. In this paper, the effect of sintering technology of bricks on their performance is discussed. The compressive strength of fired bricks is first increased and then decreased with an increase in the sintering temperature, the compressive strength of bricks prepared by the isostatic compaction shaping is higher than that of bricks prepared by the plastic shaping under the same conditions. The compressive strength of bricks reaches 28 MPa when sintered at 1150 oC by using a 20MPa isostatic compaction shaping method. The compressive strength of bricks is first increased and then decreased by prolonging the holding time, the compressive strength of bricks reaches 28.9MPa when sintered at 1150 oC for 2 h.

Effect of synthesis conditions on the particle size and morphology of YAG powder

Jie-Guang Song,Fang Wang,Ming-Han Xu,Yin-Yan Ju,Yang-Liang Li,Shi-Bin Li,Gang-Chang Ji 한양대학교 세라믹연구소 2012 Journal of Ceramic Processing Research Vol.13 No.2

Yttrium aluminum garnet (YAG) is currently a widely applied structural and functional material. To prepare highperformance YAG ceramics we prepared pure YAG powder, after calcining the precursor at 1100 ºC, by co-precipitation with ammonia as the precipitant and aluminum nitrate as well as yttrium nitrate as raw materials. The preparation conditions for the YAG precursor were a pH of 9, a titration rate of 10 ml/ minute and a reaction time of 60 minutes. The mean paricle size of the YAG powder was 11ìm. The mean particle size for the YAG powder increased with an increase in the pH and at a higher pH the YAG particles were more irregular in shape. The mean particle size and particle size distribution range of the YAG powder increased with an increase in the titration rate. For the YAG powder with a higher mean particle size, the particle size distribution range was wider but the size of most YAG particles was still small and the YAG particles were nearly spherical.

Oxidation behavior of YAG-ZrB2 ceramics prepared by spark plasma sintering

Jie-Guang Song,Da-Ming Du,Yin-Yan Ju,Yang-Liang Li,Shi-Bin Li,Gang-Chang Ji 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.4

ZrB2 and YAG are widely applied because of some excellent properties, but ZrB2 is easily oxidized in high-temperature air. To make ZrB2 ceramics have better oxidation resistance, high-density YAG-ZrB2 ceramics were prepared. The oxidation behavior of YAG-ZrB2 ceramics is investigated at different temperatures. The results indicate that the enhanced weight change differs according to the temperature range, slightly in the temperature 900-1000oC, sharply from 1100-1300 and smoothly above 1300oC. The weight change rate of YAG-ZrB2 ceramics is increased by prolonging the oxidation time, but the weight change rate of YAG-ZrB2 ceramics is gradually reduced. The oxidation layer is porous as compared to the YAG-ZrB2 ceramics layer.

Effect of raw materials on the properties of ZrB2-YAG-Al2O3 multi-phase ceramics

Jie-Guang Song,Fang Wang,Da-Ming Du,Yin-Yan Ju,Shi-Bin Li,Gang-Chang Ji,Lian-Meng Zhang 한양대학교 세라믹연구소 2014 Journal of Ceramic Processing Research Vol.15 No.2

ZrB2 belongs to a class of ceramics defined ultra-high-temperature ceramics with extremely high melting temperatures, but ZrB2 ceramics is difficultly sintered and easily oxidized. To make ZrB2 ceramics possess the high relative density and the better oxidation resistance. The effects of raw materials on the properties of ZrB2 composite were investigated. YAG and Al2O3 help for the densification of ZrB2 ceramics. Fracture toughness of sintered ceramics with coated powder is higher than that of sintered ceramics with mixed powder. The mechanical property of ZrB2-YAG-Al2O3 materials is higher than that of ZrB2-YAG materials. Oxidation layer thickness of sintered ceramics with coated powder is thinner than that of sintered ceramics with mixed powder. These results show the sintered ZrB2 based multi-phase ceramics with coated microstructure help to increase the mechanical properties and oxidation resistance. The oxidation resistance of ZrB2-YAG-Al2O3 ceramics is better than that of ZrB2-YAG materials.

Numerical analysis of concrete degradation due to chloride-induced steel corrosion

Ayinde, Olawale O.,Zuo, Xiao-Bao,Yin, Guang-Ji Techno-Press 2019 Advances in concrete construction Vol.7 No.4

Concrete structures in marine environment are susceptible to chloride attack, where chloride diffusion results in the corrosion of steel bar and further lead to the cracking of concrete cover. This process causes structural deterioration and affects the response of concrete structures to different forms of loading. This paper presents the use of ABAQUS Finite Element Software in simulating the processes involved in concrete's structural degradation from chloride diffusion to steel corrosion and concrete cover cracking. Fick's law was used for the chloride diffusion, while the mass loss from steel corrosion was obtained using Faraday's law. Pressure generated by steel corrosion product at the concrete-steel interface was modeled by applying uniform radial displacements, while concrete smeared cracking alongside the Extended Finite Element Method (XFEM) was used for concrete cover cracking simulation. Results show that, chloride concentration decreases with penetration depth, but increases with exposure time at the concrete-steel interface. Cracks initiate and propagate in the concrete cover as pressure caused by the steel corrosion product increases. Furthermore, the crack width increases with the exposure time on the surface of the concrete.

Numerical investigation on gypsum and ettringite formation in cement pastes subjected to sulfate attack

Xiao-Bao Zuo,Jia-Lin Wang,Wei Sun,Hua Li,Guang-Ji Yin 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.19 No.1

This paper uses modelling and experiment to perform a quantitative analysis for the gypsum and ettringite formations in cement pastes subjected to sulfate attack. Firstly, based on Fick’s law and chemical reaction kinetics, a diffusion model of sulfate ions in cement pastes is proposed, and then the model of the gypsum and ettringite formations is established to analyze its contents in cement pastes with corrosion time. Secondly, the corrosion experiment of the specimens with cement pastes immersed into 2.5%, 5.0% and 10.0% Na2SO4 solutions are carried out, and by using XRD-Rietveld method, the phases of powder samples from the specimens are quantitatively analyzed to obtain the contents of gypsum and ettringite in different surface depth, solution concentration and corrosion time. Finally, the contents of gypsum and ettringite calculated by the models are compared with the results from the XRD experiments, and then the effects of surface depth, corrosion time and solution concentration on the gypsum and ettringite formations in cement pastes are discussed.

MiRNA Synergistic Network Construction and Enrichment Analysis for Common Target Genes in Small-cell Lung Cancer

Zhang, Tie-Feng,Cheng, Ke-Wen,Shi, Wei-Yin,Zhang, Jin-Tao,Liu, Ke-Di,Xu, Shu-Guang,Chen, Ji-Quan Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.12

Background: Small-cell lung cancer (also known as SCLC) is an aggressive form and untreated patients generally die within about 3 months. To obtain further insight into mechanism underlying malignancy with this cancer, an miRNA synergistic regulatory network was constructed and analyzed in the present study. Method: A miRNA microarray dataset was downloaded from the NCBI GEO database (GSE27435). A total of 546 miRNAs were identified to be expressed in SCLC cells. Then a miRNA synergistic network was constructed, and the included miRNAs mapped to the network. Topology analysis was also performed to analyze the properties of the synergistic network. Consequently, we could identified constitutive modules. Further, common target genes of each module were identified with CFinder. Finally, enrichment analysis was performed for target genes. Results: In this study, a miRNA synergistic network with 464 miRNAs and 2981 edges was constructed. According to the topology analysis, the topological properties between the networks constructed by LC related miRNAs and LC unrelated miRNAs were significantly different. Moreover, a module cilque0 could be identified in our network using CFinder. The module included three miRNAs (hsa-let-7c, hsa-let-7b and hsa-let-7d). In addition, several genes were found which were predicted to be common targets of cilque0. The enrichment analysis demonstrated that these target genes were enriched in MAPK signaling pathways. Conclusions: Although limitations exist in the current data, the results uncovered here are important for understanding the key roles of miRNAs in SCLC. However, further validation is required since our results were based on microarray data derived from a small sample size.