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  • 1
    Publication Date: 2019-06-01
    Description: Water-soluble and low molecular weight (Mw) β-glucans were successfully prepared by γ-irradiation of water-insoluble yeast β-glucans. The radiation dose used for the degradation of yeast β-glucan was remarkably reduced by increasing the pH of the sample or combining with hydrogen peroxide treatment. Radiation-degraded β-glucans with molecular weights in the range of 11−48 kDa reduced the total cholesterol, triglyceride, low density lipoprotein (LDL) cholesterol, and glucose levels in the blood of administered mice. The decreasing levels of both lipid and glucose indexes in the blood of tested mice strongly depended on the molecular weight of the β-glucan, and the radiation-degraded β-glucan with a molecular weight of about 25 kDa was found to be the most effective for the reduction of blood lipid and glucose levels. Particularly, the oral administration of 25 kDa β-glucan, with a daily dose of about 2 mg per head, reduced the total cholesterol, triglyceride, LDL-cholesterol, and glucose levels in the blood of tested mice to about 47.4%, 48.5%, 45.7%, and 47.2%, respectively. The effects on the reduction of blood lipid and glucose levels were also found to be stable after 20 days of stopping administration. These results indicate that the degraded β-glucan with a molecular weight of about 25 kDa prepared by γ-ray irradiation is a very promising ingredient that can be used in nutraceutical food for therapeutics of diabetic and dyslipidemia.
    Electronic ISSN: 2073-4360
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
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  • 2
    Publication Date: 2019-12-26
    Description: Ce-V-Ti and Ce-V-Ti/GO catalysts synthesized by the sol-gel method were used for the catalytic combustion of dioxins at a low temperature under simulating sintering flue gas in this paper. The catalytic mechanism of Ce-V-Ti catalysts modified with graphene oxides (GO) at a low temperature was revealed through X-ray diffractometer (XRD), Brunauer–Emmett–Teller (BET), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), H2-temperature-programmed reduction (H2-TPR) and Fourier transform infrared (FTIR). During the tests, chlorobenzene (CB) was used as a model reagent since the dioxins are poisonous. The results showed that introducing GO to Ce-V-Ti catalysts can improve the specific surface area and promote the CB adsorption on the surface of catalysts. Simultaneously, the Ce-V-Ti with 0.7 wt % GO support showed the high activity with the conversion of 60% at 100 °C and 80% at 150 °C. The adsorb ability of catalysts is strengthened by the electron interaction between GO and CB through π-π bond. In the case of Ce-V-Ti catalysts, Ce played a major catalytic role and V acted as a co-catalytic composition. After GO modification, the concentration of Ce3+ and V4+ were enlarged. The synergy between Ce3+ and V3+ played the critical role on the low-temperature performance of catalysts under sintering flue gas.
    Electronic ISSN: 1996-1944
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 3
    Publication Date: 2013-01-23
    Electronic ISSN: 1996-1944
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 4
    Publication Date: 2020-07-15
    Description: In this paper, a weight function method based on the first four terms of a Taylor’s series expansion is proposed to determine the stress intensity factors of functionally graded plates with semi-elliptical surface cracks. Cracked surfaces that are subjected to constant, linear, parabolic and cubic stress fields are considered. The weight functions for the surface, deepest and general points on the crack faces of long and deep cracked functionally graded plates are derived, which has never been done before in the literature. The accuracy of the method in this study is then validated by comparing the results with those of finite element modeling. The numerical results indicate that the derived weight functions are highly accurate and robust enough to predict the stress intensity factors for cracked functionally graded plates subjected to non-uniform stress distributions. The weight function method is therefore a time-saving technique and suitable for handling non-uniform stress fields.
    Electronic ISSN: 1996-1944
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 5
    Publication Date: 2020-04-24
    Description: The mechanical properties of the Al-Mg alloy can be enhanced by adding metallic elements, but a continuous distribution of precipitates at grain boundaries leads to intergranular corrosion during sensitization treatment. In the present work, Mn, Zn additions, water cooling and furnace cooling were executed to investigate their effects on the mechanical and corrosion properties of the Al-4.6Mg alloy. Our results show that adding Mn to Al-4.6Mg alloys may produce grain refinement and dispersion strengthening, increasing tensile strength and hardness. The presence of Mn did not affect the corrosion resistance of Al-Mg alloys. Adding Zn to the Al-4.6Mg alloy increased tensile strength and hardness, but decreased corrosion resistance. Combined, the addition of Mn and Zn to the Al-4.6Mg alloy exhibited the highest tensile strength and hardness, but seriously reduced corrosion resistance. Furnace cooling substituted for water quenching could avoid intergranular corrosion, but slightly decreased the tensile strength and hardness by 7.0% and 6.8%, respectively.
    Electronic ISSN: 1996-1944
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 6
    Publication Date: 2020-04-27
    Description: Poly(lactic acid) (PLA) represents one of the most promising and attractive bio-based polymers for green packaging. However, toughness, gas barrier and antibacterial properties of pure PLA films cannot compete with those of traditional petroleum-based active packaging plastics. To fill this gap, utilization of excellent chelating properties of phytic acid (PA), functionalized layered double hydroxides (LDHs@PA-Cu(II)) was firstly synthetized via facile deposition and chelation of one-step assembled PA-Cu(II) coordination compounds on the surface of layered clay. Furthermore, LDHs@PA-Cu(II)/PLA nanocomposites were prepared by blending LDHs@PA-Cu(II) and pure PLA via solution casting evaporation process. After adding only 1 wt % LDHs@PA-Cu(II), elongation at break and tensile strength increase by 53.0% and 18.9%, respectively, and the oxygen relative permeability decreases by 28.0%. Due to the strong interface interaction and heterogenous nucleation, the reinforcement effect of LDHs@PA-Cu(II) at low loadings is remarkable. Meanwhile, owing to the antibacterial activity of PA-Cu(II) coatings, the antibacterial rate (against Escherichia coli) of LDHs@PA-Cu(II) exceeds 99.99%. Furthermore, the corresponding LDHs@PA-Cu(II)/PLA nanocomposites also show outstanding antibacterial properties, which will be a promising candidate for active packaging application.
    Electronic ISSN: 1996-1944
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 7
    Publication Date: 2020-04-08
    Description: Hot stamping is a well-known process to produce structural automotive parts with an excellent strength-to-weight ratio. However, this process is more expensive due to the lower energy efficiency and operating cost of the traditional roller-hearth furnace. Additionally, lower ductility and toughness are commonly recognized as the main disadvantages of the current hot stamped ultra-high-strength parts. Refinement of austenite grains could be a profitable way to improve the strength of hot stamped parts. In this work, the evolution of reversed transformation in asymmetrically cryogenically rolled samples was studied in order to control the austenite. Thermomechanical simulation and heat treatment in the salt bath were used to investigate the reversed transformation process, and the typical microstructures were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Compared with symmetric prerolling, ferrite recrystallization could be remarkably inhibited by asymmetric rolling at the liquid nitrogen temperature (LNT) during the reheating process. Additionally, the nucleation of the austenite inner grains can also be promoted and the dynamics of the reversed transformation accelerated by asymmetric prerolling. Such phenomena might be very useful to refine the parent austenite grains before press hardening and enhance the new hot stamping strategy by partial fast reheating.
    Electronic ISSN: 1996-1944
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 8
    Publication Date: 2020-05-11
    Description: There are considerable resource reuse and environmental concerns regarding SiC sludge (SiCS) that results from cutting silicon ingots into wafers. In the current study, the effect of the Na2SiO3 solution/sodium hydroxide solution (NS/SS) mass ratio and SiCS amount on metakaolin geopolymers was found during geopolymerization system performance. The results indicate that while NS/SS ratio was relatively low, increasing the NaOH content resulted in a sufficient amount of OH− in the system to increase the solubility and hinder polycondensation, as indicated by the bulk density and setting-time results; since the polycondensation was inhibited, the mechanical strength was reduced. This study demonstrated that a geopolymer can be formed from a substitution of 10% SiCS and with an NS/SS ratio of 1.6, and that this geopolymer is a feasible material.
    Electronic ISSN: 1996-1944
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 9
    Publication Date: 2020-05-14
    Description: Tetracalcium phosphate (TTCP), a potential biological scaffold material, has attracted increasing interest for bone regeneration applications due to its good biodegradability and biocompatibility. In this research, three-dimensional porous TTCP scaffolds were manufactured via selective laser sintering (SLS), and an in-depth and meticulous study on the influence of laser power on the microstructure and mechanical properties of TTCP scaffolds was performed. The results showed that the TTCP particles fused together and formed a solid object due to the decrease in the number of micro-pores in the scaffold as the laser power increased from 6 W to 9 W. The maximum compressive strength that the scaffold could withstand and the strength of the fracture toughness were 11.87 ± 0.64 MPa and 1.12 ± 0.1 MPa·m1/2, respectively. When the laser power increased from 9 W to 10 W, the TTCP grains grew abnormally, resulting in diminished mechanical properties. The bioactivity tests showed that the surfaces of the scaffolds were entirely covered by bone-like apatite layers after soaking in simulated body fluid (SBF) for three days, indicating that the scaffolds exhibit excellent bioactivity. Moreover, cell experiments showed that the TTCP scaffolds had good biocompatibility. This study indicated that SLS-fabricated TTCP scaffolds may be a promising candidate for bone regeneration applications.
    Electronic ISSN: 1996-1944
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 10
    Publication Date: 2020-03-30
    Description: This paper explores the microstructural evolution characteristics of tailings sand samples of different types of infiltration failure during the infiltration failure process. The homemade small infiltration deformation instrument is used to test the infiltration failure characteristics of the tailings sand during the infiltration failure process. Evolutionary characteristics of the internal microstructure pores and particle distribution were also studied. Using CT (computerized tomography) technology to establish digital image information, the distribution of the microscopic characteristics of the particle distribution and pore structure after tailing sand infiltration were studied. Microscopic analysis was also performed to analyze the microscopic process of infiltration and destruction, as well as to see the microscopic structural characteristics of the infiltration and destruction of the total tailings. The test results show that there are obvious differences in the microstructure characterization of fluid soil and piping-type infiltration failures. Microstructure parameters have a certain functional relationship with macrofactors. Combining the relationship between macrophysical and mechanical parameters and microstructural parameters, new ideas for future research and the prevention of tailings sand infiltration and failure mechanisms is provided.
    Electronic ISSN: 1996-1944
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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