Mechanical Heterogeneity of Heat-Resistant EV31A Magnesium Alloy with Large Size Processed by Direct-Chill Casting

Deping Zhang,Boqiong Li,Chaojie Che,Baosheng Liu,Peng Cheng,Yali Zhao,Jinhui Zhang,Liren Cheng 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.10

High quality of large-sized EV31A benchmark alloy was fabricated by direct-chill casting, without significant composition segregation along its radial direction. As-cast samples show noticeable mechanical heterogeneity, such as strength decreasing but ductility increasing from the surface to the center positions of the ingot. After heat treatment, however, mechanical properties of the alloy are nearly the same in each position, indicating mechanical homogeneity, which is mainly attributed to the strengthening mechanism transition from grain-boundary hardening in as-cast samples to precipitation hardening in peak-aged samples. In addition, we found that solute hardening is the athermal strengthening which contributes more to high-temperature strength than precipitation hardening, as evidenced by lower strength loss from 25 to 250 °C in T4-treated sample than in peak-aged sample. Solute hardening effect is thermally stable and extends to high temperatures, which favors the retention of linear strain hardening by retarding dynamic recovery. This work thus provides new insight into designing heat-resistant Mg alloys and understanding mechanical heterogeneity of large-scale Mg alloy ingots.

Synthesis and characterization of a new cellulose ether derivative: sodium levulinate cellulose

Ananda S. Amarasekara,Lauren J. Leday,Deping Wang,Cristian D. Gutierrez Reyes 한국고분자학회 2023 Macromolecular Research Vol.31 No.10

Sodium levulinate cellulose (SLC) was prepared as a new longer carbon chain analog for carboxymethyl cellulose (CMC) in 66–94% yield using the Williamson ether synthesis reaction between sodium hydroxide treated cellulose and brominated levulinic acid in aqueous iso-propanol medium under thermal and microwave conditions. Levulinate cellulose ether produced was characterized by FT-IR, TG–DTA, X-ray and proton NMR. The thermal reactions carried out at 90 °C for 3 and 24 h gave SLC products with degrees of substitutions of 0.48 and 0.86, respectively, whereas the microwave synthesis product showed a degree of substitution of 0.32 as determined by ASTM D1439-03 method used for CMC.

Fluctuation in operational energy efficiency of ships and its implications for performance appraisal

Zhang Shuang,Yuan Haichao,Sun Deping 대한조선학회 2021 International Journal of Naval Architecture and Oc Vol.13 No.1

This paper develops a dynamic regression model to quantify the contribution of key external factors to operational energy efficiency of ships. On this basis, kernel density estimation is applied to explore distribution patterns of fluctuations in operational performance. An empirical analysis based on these methods show that distribution of fluctuations in Energy Efficiency Operational Indicator (EEOI) is leptokurtic and fat tailed, rather than a normal one. Around 85% of fluctuations in EEOI can be jointly explained by capacity utilization and sailing speed, while the rest depend on other external factors largely beyond control. The variations in capacity utilization and sailing speed cannot be fully passed on to the energy efficiency performance of ships, due to complex interactions between various external factors. The application of the methods is demonstrated, showing a potential approach to develop a rating mechanism for use in the legally binding framework on operational energy efficiency of ships.

Reactive Radical Species in Photocatalytic Activities of PET-Ag-TiO2 Nanoparticles Composites Under Visible Light Irradiation

Hui Zhang,Dou Wang,Cuihong Sheng,Deping Ben,Hailiang Wu,Ningtao Mao 한국섬유공학회 2021 Fibers and polymers Vol.22 No.3

In this research, the reactive radical species in photocatalytic activities of a composite photocatalyst made fromPET filaments loaded with Ag-TiO2 nanoparticles under visible light irradiation, in comparison with those of as-modifiedAg-TiO2 nanoparticles, were reported and its photocatalytic mechanism was investigated. The PET filaments were modifiedby using tetrabutyl titanate as the TiO2 precursor and silver nitrate as the dopant in a hydrothermal process. The Ag decoratedTiO2 nanoparticles were synthesized and deposited on the surfaces of PET filaments in the hydrothermal process at 120 oCfor 180 min. The morphology, phase structure, chemical binding state, and optical properties of the PET-Ag-TiO2nanoparticles composites were systemically studied by means of field emission scanning electron microscopy (FESEM), X-raydiffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL)spectroscopy, diffuse reflectance spectroscopy (DRS), and ultraviolet photoelectron spectroscopy (UPS) techniques. Thephotocatalytic activities of the PET-Ag-TiO2 nanoparticles composites were evaluated in the photodegradation of bothmethylene blue (MB) and methyl orange (MO) dyes under visible light irradiation. It was found that, unlike in the asobtainedTiO2 nanoparticles and Ag decorated TiO2 nanoparticles, the photoinduced holes (h+) were the major reactiveradical species in both PET-Ag-TiO2 composite photocatalyst and the PET filaments loaded with TiO2 nanoparticles in theMB photodegradation process. The experimental results also indicated that the PET-Ag-TiO2 nanoparticles composites led tothe improvement of the separation efficiency of photogenerated electron-hole pairs. The enhanced photocatalytic activity ofthe PET filaments coated with Ag decorated TiO2 nanoparticles was ascribed to both the incorporation of Ag nanoparticlesinto TiO2 nanoparticles and the possible infiltration of Ag/Ti nanoparticles into PET polymers. In addition, the wavelengthand intensity of monochromatic light had great influences on the photodegradation rate of dye used, which was closelycorrelated with the maximum absorption wavelength of the dye to be degraded.

Lactobacillus casei Zhang Prevents Jejunal Epithelial Damage to Early-Weaned Piglets Induced by Escherichia coli K88 via Regulation of Intestinal Mucosal Integrity, Tight Junction Proteins and Immune Factor Expression

( Yuying Wang ),( Xue Yan ),( Weiwei Zhang ),( Yuanyuan Liu ),( Deping Han ),( Kedao Teng ),( Yunfei Ma ) 한국미생물생명공학회(구 한국산업미생물학회) 2019 Journal of microbiology and biotechnology Vol.29 No.6

Farm animals such as piglets are often affected by environmental stress, which can disturb the gut ecosystem. Antibiotics were commonly used to prevent diarrhea in weaned piglets, but this was banned by the European Union due to the development of antibiotic resistance. However, the use of probiotics instead of antibiotics may reduce the risk posed by pathogenic microorganisms and reduce the incidence of gastrointestinal diseases. Therefore, this study was conducted to investigate the effects of Lactobacillus casei Zhang on the mechanical barrier and immune function of early-weaned piglets infected using Escherichia coli K88 based on histomorphology and immunology. Fourteen-day-old weaned piglets were divided into a control group and experimental groups that were fed L. casei Zhang and infected with E. coli K88 with or without prefeeding and/or postfeeding of L. casei Zhang. The L. casei Zhang dose used was 107 CFU/g diet. Jejunum segments were obtained before histological, immunohistochemical, and western blot analyses were performed. In addition, the relative mRNA expression of toll receptors and cytokines was measured. Piglets fed L. casei Zhang showed significantly increased jejunum villus height, villus height-crypt depth ratio, muscle thickness, and expression of proliferating cell nuclear antigen and tight junction proteins ZO-1 and occludin. The use of L. casei Zhang effectively reduced intestinal inflammation after infection. We found that L. casei Zhang feeding prevented the jejunum damage induced by E. coli K88, suggesting that it may be a potential alternative to antibiotics for preventing diarrhea in early-weaned piglets.

Discussion on Reasonable Clear Spacing of Twin-Tunnels in Weak Surrounding Rock: Analytical Solution and Numerical Analysis

Fangyin Wu,Chuan He,Hao Kou,Bo Wang,Wei Meng,Hailong Meng,Deping Guo 대한토목학회 2022 KSCE Journal of Civil Engineering Vol.26 No.5

Due to the limitations of the terrain and other reasons, twin-tunnels with small clear spacing are becoming more and more common. The reasonable clear spacing of twin-tunnels in weak surrounding rock is an urgent problem. In this paper, based on pressure-arch theory (PAT), the method used to calculate the loosening pressure on the surrounding rock of twin-tunnels under three cases was derived by considering the additional disturbance of the excavation on the middle rock pillar through the amplification factors of the sliding angles, k1 and k2. Taking the weak surrounding rock as an example, we discussed the effect of the clear spacing variation on the loosening pressure of the surrounding rock, and obtained the dangerous clear spacing of twin-tunnels. The accuracy and applicability of this approach were verified by the in-site data that were measured. Considering the limitation of the pressure-arch theory on a deep-buried tunnel under high geo-stress, based on the Jiuzhai valley-Mianyang highway in China, the reasonable clear spacing of twin-tunnels in weak surrounding rock at different buried depths, i.e., 400 m − 1,600 m, is discussed using the numerical simulation method. The analytical solution indicated that the loosening pressure of the inner side of the first tunnel was greater than the one of the second due to the amplification factors of the sliding angles, k1 and k2. The in-site data showed that in the weak surrounding rock mass, when k1 and k2 are taken as 1.15 and 1.3, respectively, the loosening pressure distribution law is closest to the actual situation.

Influence of raw materials ratio on performance of permeable bricks made from electric porcelain waste

Jieguang Song,Xueqing Yang,Ping Chen,Hao Xu,Deping Luo,Rongjin Liu,Zhijun Lai 한양대학교 세라믹연구소 2022 Journal of Ceramic Processing Research Vol.23 No.4

The prepared permeable bricks using electric porcelain waste as the main raw material are investigated, which improves theutilization rate of electric porcelain waste, and realizes the organic unity of recycling resource and ecological environmentprotection. The effects of different raw material ratios on the permeability coefficient, apparent porosity, compressive strength,volume shrinkage rate and microstructure properties of electric porcelain waste permeable bricks are investigated. The electricporcelain waste with a ratio of over 85 wt.% have greatly improved the utilization rate of electric porcelain waste. The resultsare shown that the water-to-material ratio or foaming agent content are increased, the porosity and water permeability of theelectric porcelain waste permeable brick are increased, but the compressive strength of the electric porcelain waste permeablebrick is decreased. The 90 wt.% electric porcelain waste, the 3 wt.% kaolin, the 5 wt.% sintering aid, and the 2 wt.% foamingagents are optimum raw materials ratios, the water-to-material ratio for 0.9 and the drying temperature at 40 oC, the sinteringtemperature at 1200 oC and holding time for 1 h are obtained the excellent performance electric porcelain waste permeablebricks. The permeability coefficient is 3.9×10−2 cm/s, the volume shrinkage rate is 37.88%, the compressive strength is 1.146MPa, and the porosity is 79.0%.

The technology and properties of sponge city permeable bricks prepared using refractory waste

Jieguang Song,Xueqing Yang,Ping Chen,Rongjin Liu,Deping Luo,Yuxuan Wei,Wenjin Yao,Jingjing Liu,Qing Zeng 한양대학교 세라믹연구소 2021 Journal of Ceramic Processing Research Vol.22 No.4

With the widespread development of sponge city projects across the country, the use of industrial permeable bricks hasincreased dramatically. My country produces a large amount of refractory waste and pollutes the environment seriously. Wasterefractory insulation bricks are used as the main raw materials, and a small amount of auxiliary raw materials are added toprepare sponge urban permeable bricks through forming and sintering processes. Through performance tests, such asporosity, flexural strength, and water permeability coefficient, the effect of process parameters on the performance ofpermeable bricks is studied, the process parameters of using refractory waste are comprehensively optimized to preparesponge urban permeable bricks, and permeable bricks are prepared for the industrialization of high-quality industrial solidwaste. Brick provides reference. Through the experimental results and analysis, the following conclusions are drawn: the rawmaterial ratio of refractory brick waste: binder: foaming agent: sintering aid is 80:10:1:9. Slurry water mill foaming occurswhen the water to material ratio is 0.5, the ball milling speed is 80 r/min, and the ball milling time is 2 h; the foaming effectand molding performance are better. In the drying stage, drying at 45 oC for 12 h has the best molding effect. The sinteringsystem at 1,300 oC and holding time of 1 h has the best sintering performance. After optimizing the process, the porosity ofthe permeable bricks can reach 48.4%, the water permeability coefficient is 2.1×10^-2 cm/s, the national permeable brick hasA-level standard, and the compressive strength is 26.8 MPa.