Influence of Initial Damage Degree on the Degradation of Concrete Under Sulfate Attack and Wetting–Drying Cycles

Yujing Lv,Wenhua Zhang,Fan Wu,Huang Li,Yunsheng Zhang,Guodong Xu 한국콘크리트학회 2020 International Journal of Concrete Structures and M Vol.14 No.5

The previous researches on the degradation process of concrete under sulfate attack mainly focus on non-damaged concrete. It may lead to an excessive evaluation of the durability of the structure, which is detrimental to the safety of the structure. In this paper, three different damage degrees of concrete specimens with non-damaged (D0) and initial damage of 10% (D₁) and 20% (D₂) were prefabricated and subjected to sulfate attack and wetting–drying cycles. With the increase of sulfate attack cycles (0, 30, 60, 90, 120, 150 cycles), the changes in mass loss, relative dynamic modulus of elasticity, and the stress–strain curve were studied. The results show that the mass of the D0 specimen had been increasing continuously before 150 sulfate attack cycles. The mass of D₁ and D₂ had been increasing before 60 cycles, and decreasing after 60 cycles. At 150 cycles, the mass loss of D0, D₁, D₂ were − 1.054%, 0.29% and 3.20%, respectively. The relative dynamic modulus of elasticity (RDME) of D0 specimen increases continuously before 90 sulfate attack cycles. After 90 cycles, the RDME gradually decreases. However, for D₁ and D₂ specimens, the RDME began to decrease after 30 cycles. The damage degree has an obvious influence on the compressive strength and elastic modulus. For the D0 specimen, the compressive strength and elastic modulus increased continuously before 90 cycles and decreased after 90 cycles. The compressive strength and elastic modulus of D₁ and D₂ specimens began to decrease after 30 cycles. The stress–strain curves of concrete with different initial damage degrees were established, and the fitting results were good. Finally, based on the analysis of experimental data, the degradation mechanism of concrete with initial damage under the sulfate wetting–drying cycle was discussed.

Study on Preparation of Core-Spun Yarn Surgical Sutures by Compositing Drug-Loaded Nanofiber Membrane with PLA and Its Controllable Drug Release Performance

Zhichao Yang,Shuqiang Liu,Jingjing Li,Gaihong Wu,Man Zhang,Fu Li,Lu Jia,Yujing Zhang,Huimin Li,Xia Liu,Jingjing Zhao,Huiqin Zhang,Shiyu Li 한국섬유공학회 2023 Fibers and polymers Vol.24 No.12

Polylactic acid (PLA) surgical suture is considered to be one of the most ideal materials for tissue closure due to its rich raw materials and excellent biological properties. However, surgical sutures face great challenges due to problems such as wound infection and tissue reaction in practical applications. In order to improve the clinical applicability of surgical sutures, we constructed a new drug-loading system for core-spun surgical sutures. The shell was composed of nanofibrous membranes composed of polyglycolic acid (PGA) and polycaprolactone (PCL) and ciprofloxacin (CIP) antibacterial drugs, and the core layer adopts PLA filament. By adjusting the composition ratio of PGA and PCL in the shell, a new mode of regulating the release rate and release cycle of the suture was constructed. According to different wound healing time, different drug release cycles of surgical suture were selected. In the study, the structure of the core-spun yarn can be clearly observed by scanning electron microscope, the higher the shell PGA content and drug loading, the faster the drug release rate. When the carrier ratio PGA/PCL was 80/20 and the drug loading was 3%, the drug release rate was the fastest and the drug release was high; finally, antibacterial experiments showed that the suture had excellent antibacterial effect and could effectively kill Staphylococcus aureus and Escherichia coli. The successful preparation of core-spun yarn surgical suture provides a new idea for the study of new antibacterial surgical suture.

Numerical analysis of wind field induced by moving train on HSR bridge subjected to crosswind

Yujing Wang,He Xia,Weiwei Guo,Nan Zhang,Shaoqin Wang 한국풍공학회 2018 Wind and Structures, An International Journal (WAS Vol.27 No.1

To investigate the characteristics of the combined wind field produced by the natural wind field and the train-induced wind field on the bridge, the aerodynamic models of train and bridge are established and the overset mesh technology is applied to simulate the movement of high-speed train. Based on ten study cases with various crosswind velocities of 0~20 m/s and train speeds of 200~350 km/h, the distributions of combined wind velocities at monitoring points around the train and the pressure on the car-body surface are analyzed. Meanwhile, the difference between the train-induced wind fields calculated by static train model and moving train model is compared. The results show that under non-crosswind condition, the train-induced wind velocity increases with the train speed while decreases with the distance to the train. Under the crosswind, the combined wind velocity is mainly controlled by the crosswind, and slightly increases with the train speed. In the combined wind field, the peak pressure zone on the headstock surface moves from the nose area to the windward side with the increase of wind velocity. The moving train model is more applicable in analyzing the train induced wind field.

Mechanism of shear deformation, failure and energy dissipation of artificial rock joint in terms of physical and numerical consideration

Xuepeng Zhang,Yujing Jiang,Gang Wang,Jiankang Liu,Dong Wang,Changsheng Wang,Satoshi Sugimoto 한국지질과학협의회 2019 Geosciences Journal Vol.23 No.3

The physical and mechanical change processes of rock are closely related to energy transformation, and its deformation and failure is an instability phenomena driven by energy exchange. This study investigated mechanism of shear deformation, failure and energy dissipation of joint using both physical and numerical direct shear tests under constant normal load (CNL) condition. Three kinds of joint surface were artificially prepared. An acoustic emission system was employed to monitor acoustic emission in physical test, and rupture frequency was recorded in numerical test to represent micro-crack development. By research of numerical micro-crack development accompanied with physical acoustic emission results, mechanism of shear deformation and failure of joints were illustrated schematically. By definition of dissipation energy, captured using the particle flow code (PFC2D), energy releasing and dissipation were discussed with microscopic damage evolution of joints. Results showed that joints under shearing present a dissipation trend of four stages including a slow rise stage, a rapid rise stage, a shock rise stage and a rapid decline stage.

Numerical analysis of wind field induced by moving train on HSR bridge subjected to crosswind

Wang, Yujing,Xia, He,Guo, Weiwei,Zhang, Nan,Wang, Shaoqin Techno-Press 2018 Wind and Structures, An International Journal (WAS Vol.27 No.1

To investigate the characteristics of the combined wind field produced by the natural wind field and the train-induced wind field on the bridge, the aerodynamic models of train and bridge are established and the overset mesh technology is applied to simulate the movement of high-speed train. Based on ten study cases with various crosswind velocities of 0~20 m/s and train speeds of 200~350 km/h, the distributions of combined wind velocities at monitoring points around the train and the pressure on the car-body surface are analyzed. Meanwhile, the difference between the train-induced wind fields calculated by static train model and moving train model is compared. The results show that under non-crosswind condition, the train-induced wind velocity increases with the train speed while decreases with the distance to the train. Under the crosswind, the combined wind velocity is mainly controlled by the crosswind, and slightly increases with the train speed. In the combined wind field, the peak pressure zone on the headstock surface moves from the nose area to the windward side with the increase of wind velocity. The moving train model ismore applicable in analyzing the train induced wind field.

EFFICIENT PRODUCTION OF BIO-GASOLINE FROM SUGAR POLYOLS OVER RU-MOLYBDENUM OXIDE CATALYSTS

Songbai Qiu,Yujing Weng,Lungang Chen,Longlong Ma,Qi Zhang,Tiejun Wang 한국신재생에너지학회 2015 AFORE Vol.2015 No.11

Vibration analysis of mountain tunnel lining built with forepoling method

Gao, Yang,Jiang, Yujing,Du, Yanliang,Zhang, Qian,Xu, Fei Techno-Press 2018 Smart Structures and Systems, An International Jou Vol.21 No.5

Nowadays, many tunnels have been commissioned for several decades, which require effective inspection methods to assess their health conditions. The ambient vibration test has been widely adopted for the damage identification of concrete structures. In this study, the vibration characters of tunnel lining shells built with forepoling method was analyzed based on the analytical solutions of the Donnell-Mushtari shell theory. The broken rock, foreploing, rock-concrete contacts between rock mass and concrete lining, was represented by elastic boundaries with normal and shear stiffness. The stiffness of weak contacts has significant effects on the natural frequency of tunnel lining. Numerical simulations were also carried out to compare with the results of the analytical methods, showing that even though the low nature frequency is difficult to distinguish, the presented approach is convenient, effective and accurate to estimate the natural frequency of tunnel linings. Influences of the void, the lining thickness and the concrete type on natural frequencies were evaluated.

Effects of Dietary Glucose on Serum Estrogen Levels and Onset of Puberty in Gilts

Li, Fangfang,Zhu, Yujing,Ding, Lan,Zhang, Yong Asian Australasian Association of Animal Productio 2016 Animal Bioscience Vol.29 No.9

Metabolic signals and the state of energy reserves have been shown to play a crucial role in the regulation of reproductive function. This study was carried out to investigate the effects of dietary glucose levels on puberty onset in gilts. Weight-matched, landrace gilts (n = 36) $162{\pm}3days$ old, weighing about $71.05{\pm}4.53kg$, were randomly assigned to 3 dietary treatment groups of 12 gilts each. The trial lasted until the onset of puberty. Gilts in each group were supplied with diets containing different levels of glucose as follows: i) starch group (SG) was free of glucose, contained 64% corn derived starch; ii) low-dose group (LDG) contained 19.2% glucose and 44.8% corn derived starch; iii) high-dose group (HDG) contained 30% glucose and 30% corn derived starch. Results indicated: i) The growth performance of gilts were not affected by the addition of glucose, but the age of puberty onset was advanced significantly (p<0.05); ii) Compared with the SG, the concentration of insulin significantly increased before puberty in HDG (p<0.05); iii) There was no difference in serum progesterone (P) levels amongst the different feed groups, however, levels of estradiol ($E_2$), luteinizing hormone, and follicle-stimulating hormone were significantly higher at puberty onset in HDG (p<0.05). Overall, our findings indicate that glucose supplementation significantly advances puberty onset, which can have practical purposes for commercial breeding.

Self-Organized Synthesis and Mechanism of SnO2@Carbon Tube-Core Nanowire

Minting Luo,Yongjun Ma,Chonghua Pei,Yujing Xing,Lixia Wen,Li Zhang 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.8

SnO2@carbon tube-core nanowire was synthesized via a facile self-organized method, which was in situ by one step via Chemical Vapor Deposition. The resulting composite was characterized by scanning electron microscopy, X-ray diffraction and transmission electron microscope. The diameter of the single nanowire is between 5 nm and 60 nm, while the length would be several tens to hundreds of micrometers. Then X-ray diffraction pattern shows that the composition is amorphous carbon and tin dioxide. Transmission electron microscope images indicate that the nanowire consists of two parts, the outer carbon tube and the inner tin dioxide core. Meanwhile, the possible growth mechanism of SnO2@carbon tube-core nanowire is also discussed.

Calcined Attapulgite Clay as Supplementary Cementing Material: Thermal Treatment, Hydration Activity and Mechanical Properties

Tao Shi,Yanming Liu,Yanlin Zhang,Yingjia Lan,Qifan Zhao,Yujing Zhao,Haobo Wang 한국콘크리트학회 2022 International Journal of Concrete Structures and M Vol.16 No.2

The present paper studied the effects of calcination temperatures (200–800 °C) on the appearance, mineral composition, and active SiO2 content in attapulgite and investigated the effects of attapulgite before and after calcination on the chemically bonded water content, the degree of reaction of cement paste, and the mechanical properties such as the flexural strength, compressive strength, and splitting-tensile strength of cement mortar. The results indicate that the calcination temperature changes the mineral composition of attapulgite, thereby affecting the hydration activity of cement-based materials. The attapulgite calcined at 500 °C (AT500) has the best enhancement on the hydration activity of cement-based materials. The calcination at 500 °C is most beneficial to the dissolution of SiO2, and the content of SiO2 reaches 20.96%. The contents of chemically bonded water in the samples incorporated with calcined attapulgite reduced and that of the samples incorporated with AT500 at 28 d is the same as that of the control group. The reaction degree of AT500 is 78.61% at 28 days. Calcined attapulgite clay can reduce the energy consumption of the cement industry and promote the sustainable development of attapulgite clay.