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  • MDPI AG  (23)
  • Liu, Hui  (23)
  • 1
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    Experimental Study and Simulation Calculation of the Chloride Resistance of Concrete under Multiple Factors
    MDPI AG ; 2021
    In:  Applied Sciences Vol. 11, No. 12 ( 2021-06-08), p. 5322-
    Details
    In: Applied Sciences, MDPI AG, Vol. 11, No. 12 ( 2021-06-08), p. 5322-
    Abstract: Cement is widely used in marine concrete, and its resistance to chloride ion corrosion has been widely considered. In this paper, based on a laboratory test, the influence of different hydrostatic pressures, coarse aggregate contents and w/c ratios on the chloride resistance performance is analyzed. Based on COMSOL finite element software, a two-dimensional cementitious materials model is established, and the simulation results are compared with the experimental results. The results show that the penetration depth of chloride ions in cement increases with the increase of the w/c ratio. Under the hydrostatic pressure of 0 MPa, when the w/c ratio is 0.35, the penetration depth of chloride ions is 7.4 mm, and the simulation result is 8.0 mm. When the w/c ratio is 0.45, the penetration depth of chloride ions is 9.3 mm, and the simulation result is 9.9 mm. When the w/c ratio is 0.55, the penetration depth of chloride ions is 12.9 mm, and the simulation result is 12.1 mm. Under different hydrostatic pressures, the penetration depth of chloride ions obviously changes, and with the increase in hydrostatic pressure, the penetration depth of chloride ions deepens. Under the w/c ratio of 0.35, when the hydrostatic pressure is 0.5 MPa, the penetration depth of chloride ions is 11.3 mm, and the simulation result is 12.1 mm. When the hydrostatic pressure is 1.0 MPa, the penetration depth of chloride ions is 16.2 mm, and the simulation result is 17.5 mm.
    Type of Medium: Online Resource
    ISSN: 2076-3417
    URL: Article
    DOI: 10.3390/app11125322
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2704225-X
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  • 2
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    Effects of Boric Acid Ester Modified Magnesium Borate Whisker on the Mechanical Properties and Crystallization Kinetics of Polypropylene Composites
    MDPI AG ; 2020
    In:  Materials Vol. 13, No. 7 ( 2020-04-05), p. 1698-
    Details
    In: Materials, MDPI AG, Vol. 13, No. 7 ( 2020-04-05), p. 1698-
    Abstract: Polypropylene (PP) is notch sensitive and brittle under severe conditions of deformation, limiting wider range of its usage as a structural load-bearing polymer. Hence, in this work the magnesium borate whisker (MBw), with similar mechanical properties to carbon fiber but much less expensive than polycrystalline silicon carbide, was modified by boric acid ester (BAE) and then used to fabricate PP composites. The mechanical properties, morphology, and non-isothermal crystallization property of virgin PP, PP/MBw, and PP/BAE-MBw composites were studied through mechanical testing, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC), respectively. The non-isothermal crystallization data was analyzed via Mo, Kissinger, and Dobreva methods. The results reveal that the incorporation of BAE-MBw into PP matrix results in higher tensile strength and impact strength than those of virgin PP and PP/MBw composite. The activation energies based on Kissinger were 190.20 kJ/mol for virgin PP, 206.59 kJ/mol for PP/MBw, and 218.98 kJ/mol for PP/BAE-MBw. The nucleation activities of whiskers determined by the Dobreva model were 0.86 for PP/MBw and 0.75 for PP/BAE-MBw. As a result, the whiskers, especially the modified whiskers, act as active substrates to facilitate heterogeneous nucleation, which leads to an increase in crystallization rate.
    Type of Medium: Online Resource
    ISSN: 1996-1944
    URL: Article
    DOI: 10.3390/ma13071698
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2487261-1
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  • 3
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    N-Doped Biochar as a New Metal-Free Activator of Peroxymonosulfate for Singlet Oxygen-Dominated Catalytic Degradation of Acid Orange 7
    MDPI AG ; 2021
    In:  Nanomaterials Vol. 11, No. 9 ( 2021-09-02), p. 2288-
    Details
    In: Nanomaterials, MDPI AG, Vol. 11, No. 9 ( 2021-09-02), p. 2288-
    Abstract: In this paper, using rice straw as a raw material and urea as a nitrogen precursor, a composite catalyst (a nitrogen-doped rice straw biochar at the pyrolysis temperature of 800 °C, recorded as NRSBC800) was synthesized by one-step pyrolysis. NRSBC800 was then characterized using XPS, BET, TEM and other technologies, and its catalytic performance as an activator for permonosulfate (PMS) to degrade acid orange 7 (AO7) was studied. The results show that the introduction of N-doping significantly improved the catalytic performance of NRSBC800. The NRSBC800/PMS oxidation system could fully degrade AO7 within 30 min, with the reaction rate constant (2.1 × 10 −1 min−1) being 38 times that of RSBC800 (5.5 × 10−3 min−1). Moreover, NRSBC800 not only had better catalytic performance than traditional metal oxides (Co3O4 and Fe3O4) and carbon nanomaterial (CNT) but also received less impact from environmental water factors (such as anions and humic acids) during the catalytic degradation process. In addition, a quenching test and electron paramagnetic resonance (EPR) research both indicated that AO7 degradation relied mainly on non-free radical oxidation (primarily singlet oxygen (1O2)). A recycling experiment further demonstrated NRSBC800’s high stability after recycling three times.
    Type of Medium: Online Resource
    ISSN: 2079-4991
    URL: Article
    DOI: 10.3390/nano11092288
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
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  • 4
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    Design and Experiments of Electro-Hydrostatic Actuator for Wheel-Legged Robot with Fast Force Control Response
    MDPI AG ; 2023
    In:  Machines Vol. 11, No. 7 ( 2023-06-29), p. 685-
    Details
    In: Machines, MDPI AG, Vol. 11, No. 7 ( 2023-06-29), p. 685-
    Abstract: The wheel-legged robot combines the functions of wheeled vehicles and legged robots: high speed and high passability. However, the limited performance of existing joint actuators has always been the bottleneck in the actual applications of large wheel-legged robots. This paper proposed a highly integrated electro-hydrostatic actuator (EHA) to enable high-dynamic performance in giant wheel-legged robots ( 〉 200 kg). A prototype with a high force-to-weight ratio was developed by integrating a micropump, a miniature spring accumulator, and a micro-symmetrical cylinder. The prototype achieves a large output force of more than 9400 N and a high force-to-weight ratio of more than 2518 N/kg. Compared with existing EHA-based robots, it has a higher force-to-weight ratio and can bear larger loads. A detailed EHA model was presented, and controllers were designed based on sliding mode control and PID methods to control the output position and force of the piston. The model’s accuracy is improved by identifying uncertain parameters such as friction and leakage coefficient. Finally, both simulations and experiments were carried out. The results verified the fast response of force control (step response within 50 ms, the force tracking control frequency about 6.7 Hz) and the developed EHA’s good potential for future large wheel-legged robots.
    Type of Medium: Online Resource
    ISSN: 2075-1702
    URL: Article
    DOI: 10.3390/machines11070685
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2704328-9
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  • 5
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    Changes in Carotenoid Concentration and Expression of Carotenoid Biosynthesis Genes in Daucus carota Taproots in Response to Increased Salinity
    MDPI AG ; 2022
    In:  Horticulturae Vol. 8, No. 7 ( 2022-07-17), p. 650-
    Details
    In: Horticulturae, MDPI AG, Vol. 8, No. 7 ( 2022-07-17), p. 650-
    Abstract: Studying the changes of carotenoids in the taproot of carrots under salt treatment is helpful to probe the salt stress response mechanism of carrots. The carotenoid concentration and the expression profiles of 10 carotenoid-related genes were determined in two carrot cultivars with different taproot colors. Under salt stress, the biosynthesis of carotenoids in the taproot of both ‘KRD’ and ‘BHJS’ was activated. RT-qPCR manifested that the expression levels of DcPSY1, DcPSY2, DcZDS1, DcCRT1 and DcCRT2 increased significantly in both ‘KRD’ and BHJS’ under salt stress, but DcCHXE transcripts decreased and DcPDS transcripts maintained a basal level compared to that of the control. In the taproot of ‘KRD’, the expression level of DcLCYB, DcLCYE and DcCHXB1 climbed dramatically. However, there was no significant change in the taproot of ‘BHJS’. The study showed that salt stress can stimulate the biosynthesis of carotenoids. The accumulation of lutein in the taproots of ‘KRD’ and ‘BHJS’ may be mainly attributed to the variation in DcLCYE and DcCHXB1 transcripts. The increase in β-carotene accumulation is speculated to increase salt tolerance.
    Type of Medium: Online Resource
    ISSN: 2311-7524
    URL: Article
    DOI: 10.3390/horticulturae8070650
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2813983-5
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  • 6
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    Degradation of the UV Filter Benzophenone-4 by Ferrate (VI) in Aquatic Environments
    MDPI AG ; 2022
    In:  Processes Vol. 10, No. 9 ( 2022-09-10), p. 1829-
    Details
    In: Processes, MDPI AG, Vol. 10, No. 9 ( 2022-09-10), p. 1829-
    Abstract: This work demonstrates the potential utility of ferrate(VI)-based advanced oxidation processes for the degradation of a representative UV filter, BP-4. The operational parameters of oxidant dose and temperature were determined with kinetic experiments. In addition, the effects of water constituents including anions (Cl−, HCO3−, NO3−, SO42−), cations (Na+, K+, Ca2+, Mg2+, Cu2+, Fe3+), and humic acid (HA) were investigated. Results suggested that the removal rate of BP-4 (5 mg/L) could reach 95% in 60 min, when [Fe(VI)]:[BP-4] = 100:1, T = 25 °C and pH = 7.0, The presence of K+, Cu2+ and Fe3+ could promote the removal of BP-4, but Cl−, SO42−, NO3−, HA and Na+ could significantly inhibit the removal of BP-4. Furthermore, this Fe(VI) oxidation processes has good feasibility in real water samples. These results may provide useful information for the environmental elimination of benzophenone-type UV filters by Fe(VI).
    Type of Medium: Online Resource
    ISSN: 2227-9717
    URL: Article
    DOI: 10.3390/pr10091829
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2720994-5
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  • 7
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    Vacuum Thermal Treated Ni-CeO2/SBA-15 Catalyst for CO2 Methanation
    MDPI AG ; 2018
    In:  Nanomaterials Vol. 8, No. 10 ( 2018-09-26), p. 759-
    Details
    In: Nanomaterials, MDPI AG, Vol. 8, No. 10 ( 2018-09-26), p. 759-
    Abstract: Ni-CeO2/SBA-15-V catalyst was prepared by the impregnation method with vacuum thermal treatment and used for CO2 methanation reaction. Compared with Ni-CeO2/SBA-15-air catalyst with thermal treatment in air, the reduced Ni-CeO2/SBA-15-V catalyst with vacuum thermal treatment exhibited higher Ni dispersion and smaller Ni particle size. In CO2 methanation reaction, the Ni-CeO2/SBA-15-V catalyst was more active and selective than the Ni-CeO2/SBA-15-air catalyst. The good activity and selectivity of Ni-CeO2/SBA-15-V catalyst should be due to highly dispersed Ni in contact with small CeO2 particles.
    Type of Medium: Online Resource
    ISSN: 2079-4991
    URL: Article
    DOI: 10.3390/nano8100759
    Language: English
    Publisher: MDPI AG
    Publication Date: 2018
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  • 8
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    CoMn2O4 Catalyst Prepared Using the Sol-Gel Method for the Activation of Peroxymonosulfate and Degradation of UV Filter 2-Phenylbenzimidazole-5-sulfonic Acid (PBSA)
    MDPI AG ; 2019
    In:  Nanomaterials Vol. 9, No. 5 ( 2019-05-20), p. 774-
    Details
    In: Nanomaterials, MDPI AG, Vol. 9, No. 5 ( 2019-05-20), p. 774-
    Abstract: In this study, a bimetallic oxide catalyst of cobalt-manganese (CoMn2O4) was synthesized using the sol-gel method, and it was then characterized using a variety of techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) spectroscopy, X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption–desorption isotherms. The obtained novel catalyst, i.e., CoMn2O4, was then used as an activator of peroxymonosulfate (PMS) for the catalytic degradation of a commonly-used UV filter, 2-phenylbenzimidazole-5-sulfonic acid (PBSA) in water. The effects of various factors (e.g., catalyst dosage, PMS concentration, reaction temperature, and pH) in the process were also evaluated. Chemical scavengers and electron paramagnetic resonance (EPR) tests showed that the •OH and SO4•− were the main reactive oxygen species. Furthermore, this study showed that CoMn2O4 is a promising catalyst for activating PMS to degrade the UV filters.
    Type of Medium: Online Resource
    ISSN: 2079-4991
    URL: Article
    DOI: 10.3390/nano9050774
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
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  • 9
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    Degradation of UV Filter Ethyl 4-Aminobenzoate (Et-PABA) Using a UV-Activated Persulfate Oxidation Process
    MDPI AG ; 2019
    In:  Applied Sciences Vol. 9, No. 14 ( 2019-07-18), p. 2873-
    Details
    In: Applied Sciences, MDPI AG, Vol. 9, No. 14 ( 2019-07-18), p. 2873-
    Abstract: In this paper, the ultraviolet/persulfate (UV/PDS) combined oxidation process was used to remove the ethyl 4-aminobenzoate (Et-PABA), one of the typical 4-aminobenzoic acid (PABA)-type UV filters. The effects of various factors on the removal of Et-PABA using the UV/PDS process were investigated, and the degradation mechanisms of Et-PABA were explored. The results showed that the UV/PDS process can effectively remove 98.7% of Et-PABA within 30 min under the conditions: UV intensity of 0.92 mW·cm−2, an initial concentration of Et-PABA of 0.05 mM, and a PDS concentration of 2 mM. The removal rate of Et-PABA increased with the increase in PDS dosage within the experimental range, whereas humic acid (HA) had an inhibitory effect on Et-PABA removal. Six intermediates were identified based on HPLC–MS and degradation pathways were then proposed. It can be foreseen that the UV/PDS oxidation process has broad application prospects in water treatment.
    Type of Medium: Online Resource
    ISSN: 2076-3417
    URL: Article
    DOI: 10.3390/app9142873
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
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  • 10
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    Insights into the Modifying Effect of Ga on Cu-Based Catalysts for Hydrogenation of Hydroxypivalaldehyde to Neopentyl Glycol
    MDPI AG ; 2023
    In:  Catalysts Vol. 13, No. 4 ( 2023-03-30), p. 673-
    Details
    In: Catalysts, MDPI AG, Vol. 13, No. 4 ( 2023-03-30), p. 673-
    Abstract: Cu-based catalysts, modified by gallium addition via the stepwise co-precipitation method, were studied for the liquid phase hydrogenation of hydroxypivalaldehyde (HPA) to neopentyl glycol (NPG). Through physico-chemical techniques, the effects of gallium introduction on the Cu trimetallic catalyst performance and the reaction mechanism of HPA hydrogenation were discussed. The characterization results showed that gallium introduction can influence the dispersion, reduction, and distribution of active Cu species, as well as their reactivity. Herein, the catalyst with 2 wt% gallium addition exhibited excellent catalytic performance with HPA conversion rate and NPG selectivity of 93.5% and 95.5%, at a reaction pressure of 3 MPa, temperature of 110 °C, hydrogen-aldehyde ratio (molar ratio) 10:1, and liquid space-time at a speed of 8.4 h−1. The good performance could be attributed to gallium doping tending to dynamically tune the interaction between the components, increasing Cu dispersion and the distributions of Cu+ and Cu0 species on the catalyst surfaces.
    Type of Medium: Online Resource
    ISSN: 2073-4344
    URL: Article
    DOI: 10.3390/catal13040673
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2662126-5
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