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  • MDPI AG  (11)
  • 1
    Online Resource
    Online Resource
    Self-Photoluminescence of Unzipped Multi-Walled Carbon Nanotubes
    MDPI AG ; 2021
    In:  Nanomaterials Vol. 11, No. 7 ( 2021-06-22), p. 1632-
    Details
    In: Nanomaterials, MDPI AG, Vol. 11, No. 7 ( 2021-06-22), p. 1632-
    Abstract: Unzipping of carbon nanotubes (CNTs) has been widely explored to obtain new nanocarbon structures with promising properties. In this work, we report that unzipping of CNTs according to the well-established modified Hummers method produces unzipped CNTs (uCNTs) that exhibit self-photoluminescence that depends on the diameter of pristine CNTs. The uCNTs were characterized using FTIR spectroscopy, XRD, XPS, and Raman spectroscopy indicating that unzipping is accompanied by the introduction of defects and oxygen-containing functional groups. The morphology of CNTs and uCNTs was determined by TEM showing longitude unzipping of CNTs. Our study shows that increasing the diameter of pristine CNTs results in decreasing the edge etching effect and decreasing the functionality of uCNTs. Based on the UV-Vis spectra, the band gap of uCNTs was calculated using the Kubelka–Munk function. The band gap of uCNTs increased with decreasing diameter of pristine CNTs. The uCNTs exhibited photoluminescence with a good emission in the visible light region. The uCNTs with the largest band gap and the highest oxygen content had the strongest fluorescence intensity. Moreover, different metal ions produced different degrees of fluorescence quenching for uCNT-15, which verified the self-photoluminescence of uCNTs.
    Type of Medium: Online Resource
    ISSN: 2079-4991
    URL: Article
    DOI: 10.3390/nano11071632
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2662255-5
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  • 2
    Online Resource
    Online Resource
    Research on Defect Detection in Kubo Peach Based on Hyperspectral Imaging Technology Combined with CARS-MIV-GA-SVM Method
    MDPI AG ; 2023
    In:  Foods Vol. 12, No. 19 ( 2023-09-27), p. 3593-
    Details
    In: Foods, MDPI AG, Vol. 12, No. 19 ( 2023-09-27), p. 3593-
    Abstract: Due to the dark red surface of ripe fresh peaches, their internal injury defects cannot be detected using the naked eye and conventional images. The rapid and accurate detection of fresh peach defects can improve the efficiency of fresh peach classification. The goal of this paper was to develop a nondestructive approach to simultaneously detecting internal injury defects and external injuries in fresh peaches. First, we collected spectral data from 347 Kubo peach samples using hyperspectral imaging technology (900–1700 nm) and carried out pretreatment. Four methods (the competitive adaptive reweighting algorithm (CARS), the combination of CARS and the average influence value algorithm (CARS-MIV), the combination of CARS and the successive projections algorithm (CARS-SPA), and the combination of CARS and uninformative variable elimination (CARS-UVE)) were used to extract the characteristic wavelength. Based on the characteristic wavelength extracted using the above methods, a genetic algorithm optimization support vector machine (GA-SVM) model and a least-squares support vector machine (LS-SVM) model were used to establish classification models. The results show that the combination of CARS and other feature wavelength extraction methods can effectively improve the prediction accuracy of the model when the number of wavelengths is small. Among them, the discriminant accuracy of the CARS-MIV-GA-SVM model reaches 93.15%. In summary, hyperspectral imaging technology can accomplish the accurate detection of Kubo peaches defects, and provides feasible ideas for the automatic classification of Kubo peaches.
    Type of Medium: Online Resource
    ISSN: 2304-8158
    URL: Article
    DOI: 10.3390/foods12193593
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2704223-6
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  • 3
    Online Resource
    Online Resource
    Hybrid Prediction Model of the Temperature Field of a Motorized Spindle
    MDPI AG ; 2017
    In:  Applied Sciences Vol. 7, No. 10 ( 2017-10-22), p. 1091-
    Details
    In: Applied Sciences, MDPI AG, Vol. 7, No. 10 ( 2017-10-22), p. 1091-
    Type of Medium: Online Resource
    ISSN: 2076-3417
    URL: Article
    DOI: 10.3390/app7101091
    Language: English
    Publisher: MDPI AG
    Publication Date: 2017
    detail.hit.zdb_id: 2704225-X
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  • 4
    Online Resource
    Online Resource
    Role of Magnesium Perrhenate in an Oil/Solid Mixed System for Tribological Application at Various Temperatures
    MDPI AG ; 2018
    In:  Materials Vol. 11, No. 9 ( 2018-09-18), p. 1754-
    Details
    In: Materials, MDPI AG, Vol. 11, No. 9 ( 2018-09-18), p. 1754-
    Abstract: Magnesium perrhenate used as a lubricating additive was prepared by an aqueous solution method in this paper, and was suspended in a base oil poly alpha olefin (PAO6) with the aid of surface active agents (SA). The thermal stability of the mixed oil with/without magnesium perrhenate and surface active agents was investigated by thermogravimetry testing. The influences of magnesium perrhenate as solid lubricating additive on the extreme pressure performance and the friction-reducing properties over a wide temperature range of the mixed lubricants were determined by four-ball tests and ball-on-disc frictional tests for the commercially available silicon nitride ball and a Ni-base superalloy frictional pair. The results revealed that the added magnesium perrhenate did not obviously affect the thermostability and oxidation resistance of the base oil. Meanwhile, it minimized the coefficients of friction and wear scar diameter to a certain extent in the four-ball experimental conditions. Ball-on-disc rubbing tests suggested the mixed oil had a similar lubricating performance to the base oil below the decomposition temperature point. The most significant advancement was the impressive antifriction improvement at the high temperature range, while the friction coefficients of the oil containing magnesium perrhenate compound were obviously below that of the base stock. This better tribological performance of the mixed lubricant was attributed to the native shear susceptible property and chemical stability of magnesium perrhenate under high temperature conditions, which could form an effective durable and stable antifriction layer with the oxides from the superalloy matrix, thereby decreasing the friction in the high-temperature environment.
    Type of Medium: Online Resource
    ISSN: 1996-1944
    URL: Article
    DOI: 10.3390/ma11091754
    Language: English
    Publisher: MDPI AG
    Publication Date: 2018
    detail.hit.zdb_id: 2487261-1
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  • 5
    Online Resource
    Online Resource
    The Magnetic Proximity Effect Induced Large Valley Splitting in 2D InSe/FeI2 Heterostructures
    MDPI AG ; 2020
    In:  Nanomaterials Vol. 10, No. 9 ( 2020-08-21), p. 1642-
    Details
    In: Nanomaterials, MDPI AG, Vol. 10, No. 9 ( 2020-08-21), p. 1642-
    Abstract: The manipulation of valley splitting has potential applications in valleytronics, which lacks in pristine two-dimensional (2D) InSe. Here, we demonstrate that valley physics in InSe can be activated via the magnetic proximity effect exerted by ferromagnetic FeI2 substrate with spin-orbit coupling. The valley splitting energy can reach 48 meV, corresponding to a magnetic exchange field of ~800 T. The system also presents magnetic anisotropy behavior with its easy magnetization axis tunable from in-plane to out-of-plane by the stacking configurations and biaxial tensile strain. The d-orbital-resolved magnetic anisotropic energy contributions indicate that the tensile strain effect arises from the increase of hybridization between minority Fe dxy and dx2−y2 states. Our results reveal that the magnetic proximity effect is an effective approach to stimulate the valley properties in InSe to extend its spintronic applications, which is expected to be feasible in other group-III monochalcogenides.
    Type of Medium: Online Resource
    ISSN: 2079-4991
    URL: Article
    DOI: 10.3390/nano10091642
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2662255-5
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  • 6
    Online Resource
    Online Resource
    Effects of Different Low-Temperature Storage Methods on the Quality and Processing Characteristics of Fresh Beef
    MDPI AG ; 2023
    In:  Foods Vol. 12, No. 4 ( 2023-02-11), p. 782-
    Details
    In: Foods, MDPI AG, Vol. 12, No. 4 ( 2023-02-11), p. 782-
    Abstract: Low-temperature storage has become the most common way for fresh meat storage because of its lower cost and better preservation effect. Traditional low-temperature preservation includes frozen storage and refrigeration storage. The refrigeration storage has a good fresh-keeping effect, but the shelf life is short. Frozen storage has a long shelf life, but it has a great impact on the quality of meat structure and other qualities, and cannot achieve a complete “fresh-keeping” effect. With the development of food processing storage and freezing technology, two new storage methods, ice temperature storage and micro-frozen storage, have attracted more attention. In this paper, the effects of different low-temperature storage methods on the sensory, physicochemical properties, myofibrillar protein oxidation, microstructure, and processing characteristics of fresh beef were studied. The optimal storage methods under different storage requirements were analyzed to reveal the mechanism and efficacy of ice temperature storage and micro-frozen storage technology, as well as the advantages compared with traditional low-temperature refrigeration. It has practical significance for guiding the application of low-temperature storage of fresh meat. Finally, this study concluded that the longest shelf life could be achieved by frozen storage, and the best preservation effect was achieved during the shelf life of ice temperature storage, and the effect of micro-frozen storage on the myofibrillar protein oxidation and microstructure was the best.
    Type of Medium: Online Resource
    ISSN: 2304-8158
    URL: Article
    DOI: 10.3390/foods12040782
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2704223-6
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  • 7
    Online Resource
    Online Resource
    A High Spectral Entropy (SE) Memristive Hidden Chaotic System with Multi-Type Quasi-Periodic and its Circuit
    MDPI AG ; 2019
    In:  Entropy Vol. 21, No. 10 ( 2019-10-22), p. 1026-
    Details
    In: Entropy, MDPI AG, Vol. 21, No. 10 ( 2019-10-22), p. 1026-
    Abstract: As a new type of nonlinear electronic component, a memristor can be used in a chaotic system to increase the complexity of the system. In this paper, a flux-controlled memristor is applied to an existing chaotic system, and a novel five-dimensional chaotic system with high complexity and hidden attractors is proposed. Analyzing the nonlinear characteristics of the system, we can find that the system has new chaotic attractors and many novel quasi-periodic limit cycles; the unique attractor structure of the Poincaré map also reflects the complexity and novelty of the hidden attractor for the system; the system has a very high complexity when measured through spectral entropy. In addition, under different initial conditions, the system exhibits the coexistence of chaotic attractors with different topologies, quasi-periodic limit cycles, and chaotic attractors. At the same time, an interesting transient chaos phenomenon, one kind of novel quasi-periodic, and weak chaotic hidden attractors are found. Finally, we realize the memristor model circuit and the proposed chaotic system use off-the-shelf electronic components. The experimental results of the circuit are consistent with the numerical simulation, which shows that the system is physically achievable and provides a new option for the application of memristive chaotic systems.
    Type of Medium: Online Resource
    ISSN: 1099-4300
    URL: Article
    DOI: 10.3390/e21101026
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
    detail.hit.zdb_id: 2014734-X
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  • 8
    Online Resource
    Online Resource
    Experimental Study on the Lubrication and Cooling Effect of Graphene in Base Oil for Si3N4/Si3N4 Sliding Pairs
    MDPI AG ; 2020
    In:  Micromachines Vol. 11, No. 2 ( 2020-02-03), p. 160-
    Details
    In: Micromachines, MDPI AG, Vol. 11, No. 2 ( 2020-02-03), p. 160-
    Abstract: Recently, the engineering structural ceramics as friction and wear components in manufacturing technology and devices have attracted much attention due to their high strength and corrosion resistance. In this study, the tribological properties of Si3N4/Si3N4 sliding pairs were investigated by adding few-layer graphene to base lubricating oil on the lubrication and cooling under different experimental conditions. Test results showed that lubrication and cooling performance was obviously improved with the addition of graphene at high rotational speeds and low loads. For oil containing 0.1 wt% graphene at a rotational speed of 3000 r·min−1 and 40 N loads, the average friction coefficient was reduced by 76.33%. The cooling effect on Si3N4/Si3N4 sliding pairs, however, was optimal at low rotational speeds and high loads. For oil containing 0.05 wt% graphene at a lower rotational speed of 500 r·min−1 and a higher load of 140 N, the temperature rise was reduced by 19.76%. In addition, the wear mark depth would decrease when adding appropriate graphene. The mechanism behind the reduction in friction and anti-wear properties was related to the formation of a lubricating protective film.
    Type of Medium: Online Resource
    ISSN: 2072-666X
    URL: Article
    DOI: 10.3390/mi11020160
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2620864-7
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  • 9
    Online Resource
    Online Resource
    Alterations in Cellular Iron Metabolism Provide More Therapeutic Opportunities for Cancer
    MDPI AG ; 2018
    In:  International Journal of Molecular Sciences Vol. 19, No. 5 ( 2018-05-22), p. 1545-
    Details
    In: International Journal of Molecular Sciences, MDPI AG, Vol. 19, No. 5 ( 2018-05-22), p. 1545-
    Type of Medium: Online Resource
    ISSN: 1422-0067
    URL: Article
    DOI: 10.3390/ijms19051545
    Language: English
    Publisher: MDPI AG
    Publication Date: 2018
    detail.hit.zdb_id: 2019364-6
    SSG: 12
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  • 10
    Online Resource
    Online Resource
    Compensation of Hysteresis on Piezoelectric Actuators Based on Tripartite PI Model
    MDPI AG ; 2018
    In:  Micromachines Vol. 9, No. 2 ( 2018-01-26), p. 44-
    Details
    In: Micromachines, MDPI AG, Vol. 9, No. 2 ( 2018-01-26), p. 44-
    Type of Medium: Online Resource
    ISSN: 2072-666X
    URL: Article
    DOI: 10.3390/mi9020044
    Language: English
    Publisher: MDPI AG
    Publication Date: 2018
    detail.hit.zdb_id: 2620864-7
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