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  • 1
    Online Resource
    Online Resource
    Influences of Efficient Spraying of Cement-Based Slurries on Recycled Coarse Aggregate
    MDPI AG ; 2022
    In:  Materials Vol. 15, No. 21 ( 2022-11-02), p. 7730-
    Details
    In: Materials, MDPI AG, Vol. 15, No. 21 ( 2022-11-02), p. 7730-
    Abstract: The inferior property is usually one of the major problems of recycled coarse aggregate (RCA), and the utilization of the RCA is limited. Strengthening the RCA is being widely explored. Immersing the RCA in the cement-based slurry is an effective approach. However, lots of slurry and time are required, and it is difficult to integrate the immersing method into the production line of the RCA. In this paper, a circular spraying method was proposed to treat the RCA using cement-based slurry. The immersing method was also conducted to verify the feasibility of the spraying method. The crushing value (CV), 24 h water absorption (WA), apparent density (AD) and dynamic water absorption (DWA) were tested, and the micro-morphology was also observed to explore the strengthening mechanism. Results showed that the CV and the WA decreased by up to 30.0% and 14.3% when the spraying method was used. The AD was slightly influenced by the cement-based slurry regardless of the treatment method. Considering the CV, WA and AD, the comprehensive grade of the RCA could be enhanced from III to II by using the spraying method. It was worth noting that the effects of the spraying method and the immersing method were basically equivalent. When the spraying method was adopted, only about 1 min and a small amount of slurry (about 5% of the RCA mass) were required to treat the RCA.
    Type of Medium: Online Resource
    ISSN: 1996-1944
    URL: Article
    DOI: 10.3390/ma15217730
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2487261-1
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  • 2
    Online Resource
    Online Resource
    Probing the Effect of Linear and Crosslinked POE-g-GMA on the Properties of Asphalt
    MDPI AG ; 2023
    In:  Materials Vol. 16, No. 19 ( 2023-10-05), p. 6564-
    Details
    In: Materials, MDPI AG, Vol. 16, No. 19 ( 2023-10-05), p. 6564-
    Abstract: The copolymer ethylene–octene (POE) has good aging resistance and is an inexpensive asphalt additive compared to the styrene–butadiene–styrene copolymer (SBS). However, POE is easy to segregate in asphalt during storage at high temperatures. Grafting glycidyl methacrylate (GMA) onto the molecular backbone of POE (i.e., POE-g-GMA) may solve this problem, for the epoxy groups in GMA can react with the active groups in asphalt. Asphalt modified with linear and crosslinked POE-g-GMA were prepared, and the hot storage stability, physical properties and thermal oxidation aging properties were discussed in detail. The results show that linear and low-degree crosslinked POE-g-GMA-modified asphalts are storage-stable at high temperatures via measurements of the difference in softening points and small-angle X-ray scattering (SAXS) characterizations from macro and micro perspectives. The difference in softening points (ΔSP) between the upper and lower ends is no more than 3.5 °C for modified asphalts after 48 h of being in an oven at 163 °C. More importantly, the crosslinking modification of POE-g-GMA can further increase the softening point and reduce the penetration as well as rheological properties via conventional physical property, dynamic shear rheometer (DSR) and multiple-stress creep recovery (MSCR) tests. Furthermore, asphalt modified with crosslinked POE-g-GMA reveals better aging resistance via measurements of the performance retention rate and electron paramagnetic resonance (EPR) characterizations after a rolling thin film oven test (RTFOT). This work may provide further guidelines for the application of polymers in asphalt.
    Type of Medium: Online Resource
    ISSN: 1996-1944
    URL: Article
    DOI: 10.3390/ma16196564
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2487261-1
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  • 3
    Online Resource
    Online Resource
    Experimental Research on Integrated Disassembly Equipment of Super Large Offshore Oilfield Facilities
    MDPI AG ; 2023
    In:  Energies Vol. 16, No. 7 ( 2023-04-01), p. 3200-
    Details
    In: Energies, MDPI AG, Vol. 16, No. 7 ( 2023-04-01), p. 3200-
    Abstract: Based on the key module-lifting arm system, based on the principle of similarity and the hydrodynamic experimental method of a multi-dimension vibration test platform, an experimental platform for dismantling equipment is designed and built. Subsequently, the motion control model of the six-degrees-of-freedom platform is established. The three-ring control model of a servo electric cylinder is established, and the active heave compensation control of a servo electric cylinder is realized by combining position control theory. Based on the co-simulation of ADAMS and Simulink, the co-simulation system of the integrated dismantling equipment experimental platform is designed and built, and the simulation system is tested and verified. Finally, simulation and experimental verification are carried out based on the experimental platform and co-simulation system. The results show that the heave compensation rate reaches 58.3% in third-class sea conditions, 61.2% in fourth-class sea conditions, and 62.4% in fifth-class sea conditions. The integrated dismantling scheme of super large offshore oilfield facilities is feasible but, in order to ensure the safety and reliability of the operation, a heave compensation system needs to be added. The error between the simulation results and the experimental results is about 15%. Based on the analysis of external interference factors in the experiment, the error results are within a reasonable range, which proves that the experimental platform, the co-simulation system of the experimental platform, and the heave compensation strategy are accurate and effective. This study, for the first time in China, provides an effective experimental platform and co-simulation platform for the design and optimization of the integrated dismantling equipment of super large offshore oilfield facilities and lays a good research foundation for the construction and engineering demonstration of subsequent equipment.
    Type of Medium: Online Resource
    ISSN: 1996-1073
    URL: Article
    DOI: 10.3390/en16073200
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2437446-5
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  • 4
    Online Resource
    Online Resource
    Cyber-Physical Geographical Information Service-Enabled Control of Diverse In-Situ Sensors
    MDPI AG ; 2015
    In:  Sensors Vol. 15, No. 2 ( 2015-01-23), p. 2565-2592
    Details
    In: Sensors, MDPI AG, Vol. 15, No. 2 ( 2015-01-23), p. 2565-2592
    Type of Medium: Online Resource
    ISSN: 1424-8220
    URL: Article
    DOI: 10.3390/s150202565
    Language: English
    Publisher: MDPI AG
    Publication Date: 2015
    detail.hit.zdb_id: 2052857-7
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  • 5
    Online Resource
    Online Resource
    Exosomes Derived from Adipose Stem Cells Enhance Bone Fracture Healing via the Activation of the Wnt3a/β-Catenin Signaling Pathway in Rats with Type 2 Diabetes Mellitus
    MDPI AG ; 2023
    In:  International Journal of Molecular Sciences Vol. 24, No. 5 ( 2023-03-02), p. 4852-
    Details
    In: International Journal of Molecular Sciences, MDPI AG, Vol. 24, No. 5 ( 2023-03-02), p. 4852-
    Abstract: Nonunion and delayed union are common complications of diabetes mellitus that pose a serious health threat to people. There are many approaches that have been used to improve bone fracture healing. Recently, exosomes have been regarded as promising medical biomaterials for improving fracture healing. However, whether exosomes derived from adipose stem cells can promote bone fracture healing in diabetes mellitus remains unclear. In this study, adipose stem cells (ASCs) and exosomes derived from adipose stem cells (ASCs-exos) are isolated and identified. Additionally, we evaluate the in vitro and in vivo effects of ASCs-exos on the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and bone repair and the regeneration in a rat model of nonunion via Western blotting, immunofluorescence assay, ALP staining, alizarin red staining, radiographic examination and histological analysis. Compared with controls, ASCs-exos promoted BMSC osteogenic differentiation. Additionally, the results of Western blotting, radiographic examination and histological analysis show that ASCs-exos improve the ability for fracture repair in the rat model of nonunion bone fracture healing. Moreover, our results further proved that ASCs-exos play a role in activating the Wnt3a/β-catenin signaling pathway, which facilitates the osteogenic differentiation of BMSCs. All these results show that ASCs-exos enhance the osteogenic potential of BMSCs by activating the Wnt/β-catenin signaling pathway, and also facilitate the ability for bone repair and regeneration in vivo, which provides a novel direction for fracture nonunion in diabetes mellitus treatment.
    Type of Medium: Online Resource
    ISSN: 1422-0067
    URL: Article
    DOI: 10.3390/ijms24054852
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2019364-6
    SSG: 12
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  • 6
    Online Resource
    Online Resource
    Dynamic Analysis of the Lifting Arm System in the Integrated Offshore Platform Decommissioning Equipment in Complicated Sea States
    MDPI AG ; 2023
    In:  Processes Vol. 11, No. 2 ( 2023-02-20), p. 645-
    Details
    In: Processes, MDPI AG, Vol. 11, No. 2 ( 2023-02-20), p. 645-
    Abstract: With the further exploitation of offshore resources, there are more and more offshore oil and gas fields which cannot meet the production capacity requirements. So, it becomes extremely urgent to pay attention to the decommissioning of the exploitation equipment in abandoned offshore fields. A new decommissioning solution is offered by the double-ship integrated offshore platform decommissioning equipment comes. However, as the equipment will inevitably bear the combined actions of various dynamic and static loads during operation, the strength and stability of the overall unit and the connections between different modules will be greatly challenged by the complex ocean. Firstly, the dynamic characteristics of the integrated decommissioning system are analyzed in this paper. Mathematical modeling of the lifting arm system is established based on the unit characteristics matrix, and a dynamic equation of the flexible lifting arm unit and system is developed based on Lagrange’s equation and solved through numerical calculation. Secondly, modal analysis and transient analysis of the lifting arm in specific working conditions are performed according to the prototype parameters of the designed decommissioning system. Finally, according to the principle of similitude, a hydrodynamic experiment method is proposed with an integrated decommissioning multi-dimensional vibration test bench. The decommissioning system model test bench is designed and built to perform the dynamic response test, and this paper compares the test results and the simulation results for verification. The comparison verifies that the theoretical analysis and the tests prove each other valid and the results are accurate, meaning this work provides a powerful theoretical reference and offers effective research methods for future studies on super-large-scale integrated decommissioning equipment.
    Type of Medium: Online Resource
    ISSN: 2227-9717
    URL: Article
    DOI: 10.3390/pr11020645
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2720994-5
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  • 7
    Online Resource
    Online Resource
    Properties of Jet-Plated Ni Coating on Ti Alloy (Ti6Al4V) with Laser Cleaning Pretreatment
    MDPI AG ; 2019
    In:  Metals Vol. 9, No. 2 ( 2019-02-20), p. 248-
    Details
    In: Metals, MDPI AG, Vol. 9, No. 2 ( 2019-02-20), p. 248-
    Abstract: The surface mechanical properties of the Selective Laser Melting (SLM) formed Ti6Al4V samples were improved by adopting a novel laser cleaning pretreatment process combined with a jet electrodeposition process. This paper aimed to investigate the effects of different laser powers on the morphologies and adhesions of the nickel coatings. The advantages of the laser cleaning process are no grinding, no contact, high efficiency and environmental protection. The morphologies, adhesion, wear resistance, and hardness of the coatings were characterized. The results indicate that when the laser energy density reached 20% (4 J/cm2), the contaminations on the substrate and the oxide layer were removed and the crystalline grain of the coating was 15.3 nm. The shallow pits generated by laser burning increased the adhesion of the coatings. In addition, when the laser energy density increased to 6 J/cm2, a yellow oxide layer was produced on the surface of the cleaned titanium alloy. Moreover, the wear resistance of the titanium alloy after the nickel plating was improved. The wear volume was only 0.046 mm3, and the hardness increased to 1967.6 N/mm2.
    Type of Medium: Online Resource
    ISSN: 2075-4701
    URL: Article
    DOI: 10.3390/met9020248
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
    detail.hit.zdb_id: 2662252-X
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  • 8
    Online Resource
    Online Resource
    Petrogenesis of the Laoshan Suite in the Jiaodong Peninsula (Eastern China): An Oxidized Low Ba–Sr A1-Type Granite
    MDPI AG ; 2023
    In:  Minerals Vol. 13, No. 8 ( 2023-07-29), p. 1012-
    Details
    In: Minerals, MDPI AG, Vol. 13, No. 8 ( 2023-07-29), p. 1012-
    Abstract: The Jiaodong Peninsula is closely related to Mesozoic granites in terms of spatial and temporal aspects. However, the specific association between the genesis of gold mineralization and these granites remains unclear. It is also ambiguous why Laoshan-type granites, which are similar to Mesozoic granites, are not gold mineralized. In this study, we analyzed the Laoshan granites and compiled Mesozoic magmatic rock data (Linglong, Guojialing, and Weideshan suites) of the Jiaodong Peninsula. We performed whole-rock major and trace elements, LA–ICP–MS zircon U–Pb geochronology and geochemistry analyses. Our zircon U–Pb data denote that the Laoshan granite was emplaced during the 118 ± 1 Ma. The Laoshan granite is characterized by high SiO2 content (76.03–80.28 wt.%), high TFe2O3/MgO (11.1–27.1) and Ga/Al (3.0–3.5) ratios, high zircon saturation temperature (809–850 °C), and negative Eu (Eu/Eu* = 0.05–0.08) anomalies, showing A-type granite characteristics. Furthermore, the Laoshan granite is identified as an A1-type granite with low Ba (33.1–42.0 ppm) and Sr (14.1–21.0 ppm) contents. It was formed in an extensional tectonic environment induced by the subducting slab roll-back of the Paleo-Pacific Plate, mainly from the partial melting of lower crustal materials, mixed with a small amount of mantle components. Zircon trace elements indicate that the Laoshan suite had relatively high oxygen fugacity and temperature (ΔFMQ = + 2.43 to + 4.22, T-Ti in zircon (mean) = 796 °C) compared to the pre-mineralization and contemporaneous mineralization magma. We propose that oxidized adakitic magma (Weideshan suite) may contribute to the enrichment and mineralization of gold. Although Laoshan-type granite also has a high oxygen fugacity, its location is distant from the ore-controlling faults, which ultimately hinders the formation of gold mineralization. From the Jurassic to the Cretaceous, the tectonic and geochemical properties of magmatic rocks in the Jiaodong Peninsula have changed, and gold deposits are formed in such a transitional process (compression to extension, reduction to oxidation).
    Type of Medium: Online Resource
    ISSN: 2075-163X
    URL: Article
    DOI: 10.3390/min13081012
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2655947-X
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  • 9
    Online Resource
    Online Resource
    Does COVID-19 Affect the Accessibility of Outdoor Sports Venues? A Case Study in Nanchang, China
    MDPI AG ; 2023
    In:  Land Vol. 12, No. 1 ( 2023-01-03), p. 158-
    Details
    In: Land, MDPI AG, Vol. 12, No. 1 ( 2023-01-03), p. 158-
    Abstract: The COVID-19 pandemic has been a great challenge to society, the economy, and population health. It has become a significant public health event and social problem. Exploring the impact of COVID-19 on the accessibility of outdoor sports venues is crucial for people’s health. Based on spatial theory, the quantitative and qualitative analyses of outdoor sports venues’ spatial distribution and accessibility were conducted, and the epidemic’s impact on them was analyzed. The results show that: (1) The existing outdoor sports venues in Nanchang show a distribution pattern of “sparse in the north and south, and strong aggregation in the middle”. (2) As a result of the epidemic, the center of the standard deviation ellipse in outdoor sports sites shifted to the southeast, while the number of open venues decreased by 68%. (3) Before COVID-19, the entire study area could achieve full coverage by driving for 17 min, riding for 70 min, or walking for 119 min. After COVID-19, the time increased to 29, 109, and 193 min, respectively. (4) Under the high-risk scenario of COVID-19, the average walking time for people to reach outdoor sports venues increased from 6.2 min to 14.0 min in the study area, with an increase of 126%. Finally, according to the findings of this study, recommendations were made on how government departments could build or re-open outdoor sports venues during and after this epidemic.
    Type of Medium: Online Resource
    ISSN: 2073-445X
    URL: Article
    DOI: 10.3390/land12010158
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2682955-1
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  • 10
    Online Resource
    Online Resource
    A Novel Thermal Analysis Method Based on a Multi-Physics Two-Way Coupled Method and Its Application to Submersible Permanent Magnet Synchronous Motors
    MDPI AG ; 2023
    In:  Electronics Vol. 12, No. 5 ( 2023-02-27), p. 1155-
    Details
    In: Electronics, MDPI AG, Vol. 12, No. 5 ( 2023-02-27), p. 1155-
    Abstract: As a submersible permanent magnet synchronous motor (SPMSM) must function in downhole high temperature crude oil for long periods of time, the accurate prediction of its temperature rise is crucial to improve the stability of the motor. However, the analysis of its temperature field involves multiple physical fields, such as the electric field, the magnetic field, the fluid field and so on, and it is difficult to calculate accurately. Motor loss is usually loaded as a fixed value when calculating the temperature field, while in reality, the loss always changes with temperature. Therefore, the calculation of temperature is inaccurate using this one-way coupled method. In this paper, the relationship between loss and temperature is investigated and an electromagnetic-thermal fluid multi-physics two-way coupled analysis method suitable for SPMSM is proposed. The loss can be loaded as a variable by this new two-way coupled method, which significantly improves the temperature calculation accuracy. In order to prove the feasibility of the two-way coupled method, experiments based of a prototype of high torque and low speed SPMSM and cavity pump are conducted with the fiber Bragg grating (FBG) sensor measuring SPMSM temperature. Finally, the multi-physics two-way coupled method proposed in this paper is proven to be rational and feasible in the analysis of the SPMSM temperature rise.
    Type of Medium: Online Resource
    ISSN: 2079-9292
    URL: Article
    DOI: 10.3390/electronics12051155
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2662127-7
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