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  • 1
    Online Resource
    Online Resource
    High Carriage Rate of the Multiple Resistant Plasmids Harboring Quinolone Resistance Genes in Enterobacter spp. Isolated from Healthy Individuals
    MDPI AG ; 2021
    In:  Antibiotics Vol. 11, No. 1 ( 2021-12-23), p. 15-
    Details
    In: Antibiotics, MDPI AG, Vol. 11, No. 1 ( 2021-12-23), p. 15-
    Abstract: Antimicrobial-resistant bacteria causing intractable and even fatal infections are a major health concern. Resistant bacteria residing in the intestinal tract of healthy individuals present a silent threat because of frequent transmission via conjugation and transposition. Plasmids harboring quinolone resistance genes are increasingly detected in clinical isolates worldwide. Here, we investigated the molecular epidemiology of plasmid-mediated quinolone resistance (PMQR) in Gram-negative bacteria from healthy service trade workers. From 157 rectal swab samples, 125 ciprofloxacin-resistant strains, including 112 Escherichia coli, 10 Klebsiella pneumoniae, two Proteus mirabilis, and one Citrobacter braakii, were isolated. Multiplex PCR screening identified 39 strains harboring the PMQR genes (including 17 qnr,19 aac(6′)-Ib-cr, and 22 oqxA/oqxB). The genome and plasmid sequences of 39 and 31 strains, respectively, were obtained by short- and long-read sequencing. PMQR genes mainly resided in the IncFIB, IncFII, and IncR plasmids, and coexisted with 3–11 other resistance genes. The high PMQR gene carriage rate among Gram-negative bacteria isolated from healthy individuals suggests the high-frequency transmission of these genes via plasmids, along with other resistance genes. Thus, healthy individuals may spread antibiotic-resistant bacterial, highlighting the need for improved monitoring and control of the spread of antibiotic-resistant bacteria and genes in healthy individuals.
    Type of Medium: Online Resource
    ISSN: 2079-6382
    URL: Article
    DOI: 10.3390/antibiotics11010015
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2681345-2
    SSG: 15,3
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  • 2
    Online Resource
    Online Resource
    Analysis of Ductile Fracture Obtained by Charpy Impact Test of a Steel Structure Created by Robot-Assisted GMAW-Based Additive Manufacturing
    MDPI AG ; 2019
    In:  Metals Vol. 9, No. 11 ( 2019-11-10), p. 1208-
    Details
    In: Metals, MDPI AG, Vol. 9, No. 11 ( 2019-11-10), p. 1208-
    Abstract: In this study, gas metal arc welding (GMAW) was used to construct a thin wall structure in a layer-by-layer fashion using an AWS ER70S-6 electrode wire with the help of a robot. The Charpy impact test was performed after extracting samples in directions both parallel and perpendicular to the deposition direction. In this study, multiple factors related to the resulting absorbed energy have been discussed. Despite being a layered structure, homogeneous behavior with acceptable deviation was observed in the microstructure, hardness, and fracture toughness of the structure in both directions. The fracture is extremely ductile with a dimpled fibrous surface and secondary cracks. An estimate for fracture toughness based on Charpy impact absorbed energy is also given.
    Type of Medium: Online Resource
    ISSN: 2075-4701
    URL: Article
    DOI: 10.3390/met9111208
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
    detail.hit.zdb_id: 2662252-X
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  • 3
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    Online Resource
    Optimization of Process Parameters to Improve the Effective Area of Deposition in GMAW-Based Additive Manufacturing and its Mechanical and Microstructural Analysis
    MDPI AG ; 2019
    In:  Metals Vol. 9, No. 7 ( 2019-07-10), p. 775-
    Details
    In: Metals, MDPI AG, Vol. 9, No. 7 ( 2019-07-10), p. 775-
    Abstract: Additive manufacturing of metals using gas metal arc welding has an associated problem of variations of height in the onset and extinguishing parts of the weld bead. In this research, robot-assisted welding has been performed to investigate the problem, using AWS ER70S-6 low alloy steel welding electrode wire. After adjustment of welding parameters for a single-layer, single-pass, an optimal profile of welding energy was used to construct a thin wall which exhibited good forming characteristics with an effective area of approximately 97%. The resulting structure was ductile in nature with better tensile strength and microhardness as compared to the rolled steel available in industry with similar carbon content. The microstructure analysis revealed equiaxed grains in most parts of the structure having a fine grain size.
    Type of Medium: Online Resource
    ISSN: 2075-4701
    URL: Article
    DOI: 10.3390/met9070775
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
    detail.hit.zdb_id: 2662252-X
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  • 4
    Online Resource
    Online Resource
    Research Progress and Development Prospects of Enhanced GaN HEMTs
    MDPI AG ; 2023
    In:  Crystals Vol. 13, No. 6 ( 2023-06-04), p. 911-
    Details
    In: Crystals, MDPI AG, Vol. 13, No. 6 ( 2023-06-04), p. 911-
    Abstract: With the development of energy efficiency technologies such as 5G communication and electric vehicles, Si-based GaN microelectronics has entered a stage of rapid industrialization. As a new generation of microwave and millimeter wave devices, High Electron Mobility Transistors (HEMTs) show great advantages in frequency, gain, and noise performance. With the continuous advancement of material growth technology, the epitaxial growth of semiconductor heterojunction can accurately control doping level, material thickness, and alloy composition. Consequently, HEMTs have been greatly improved from material structure to device structure. Device performance has also been significantly improved. In this paper, we briefly describe MOCVD growth technology and research progress of GaN HEMT epitaxial films, examine and compare the “state of the art” of enhanced HEMT devices, analyze the reliability and CMOS compatibility of GaN devices, and look to the future directions of possible development.
    Type of Medium: Online Resource
    ISSN: 2073-4352
    URL: Article
    DOI: 10.3390/cryst13060911
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2661516-2
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  • 5
    Online Resource
    Online Resource
    Progress of Edge-Emitting Diode Lasers Based on Coupled-Waveguide Concept
    MDPI AG ; 2023
    In:  Micromachines Vol. 14, No. 6 ( 2023-06-20), p. 1271-
    Details
    In: Micromachines, MDPI AG, Vol. 14, No. 6 ( 2023-06-20), p. 1271-
    Abstract: Semiconductor lasers have developed rapidly with the steady growth of the global laser market. The use of semiconductor laser diodes is currently considered to be the most advanced option for achieving the optimal combination of efficiency, energy consumption, and cost parameters of high-power solid-state and fiber lasers. In this work, an approach for optical mode engineering in planar waveguides is investigated. The approach referred to as Coupled Large Optical Cavity (CLOC) is based on the resonant optical coupling between waveguides and allows the selection of high-order modes. The state-of-art of the CLOC operation is reviewed and discussed. We apply the CLOC concept in our waveguide design strategy. The results in both numerical simulation and experiment show that the CLOC approach can be considered a simple and cost-efficient solution for improving diode laser performance.
    Type of Medium: Online Resource
    ISSN: 2072-666X
    URL: Article
    DOI: 10.3390/mi14061271
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2620864-7
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  • 6
    Online Resource
    Online Resource
    Simulation and Experimental Study of the Characteristic Parameters of an Aircraft Cabin Temperature Control Valve
    MDPI AG ; 2022
    In:  Applied Sciences Vol. 12, No. 21 ( 2022-11-01), p. 11061-
    Details
    In: Applied Sciences, MDPI AG, Vol. 12, No. 21 ( 2022-11-01), p. 11061-
    Abstract: The temperature control valve system is essential to an aircraft. This study proposes a temperature control valve system in which the cold and hot gas exchange heat through the heat exchanger without mixing to cool the hot gas. The purpose is to maintain the stability of gas flow and temperature at the outlet of the hot path. First, a mathematical model of the temperature control valve is established, and the feasibility of the method is theoretically analyzed. After that, the temperature control valve model is meshed in Ansys, finite element analysis is performed, and the factors that may affect the outlet temperature of the hot path are qualitatively analyzed. A characteristics test experiment for the designed temperature control valve is compared with simulation results to verify the system’s feasibility. A steady-state model of the heat exchanger was obtained by a 25-point orthogonal experiment. Taking the predicted hot-side flow rate of the heat exchanger under different flow conditions as input, the heat exchanger model was fitted and dynamically analyzed, which confirmed the feasibility of PID adaptive control of the temperature control system.
    Type of Medium: Online Resource
    ISSN: 2076-3417
    URL: Article
    DOI: 10.3390/app122111061
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2704225-X
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  • 7
    Online Resource
    Online Resource
    Circulating Fluidized Bed Fly Ash Mixed Functional Cementitious Materials: Shrinkage Compensation of f-CaO, Autoclaved Hydration Characteristics and Environmental Performance
    MDPI AG ; 2021
    In:  Materials Vol. 14, No. 20 ( 2021-10-12), p. 6004-
    Details
    In: Materials, MDPI AG, Vol. 14, No. 20 ( 2021-10-12), p. 6004-
    Abstract: Circulating fluidized bed (CFB) fly ash is a by-product from CFB power generation, which is hard to utilize in cement because it contains f-CaO and SO3. This work aims to explore the mechanism of the shrinkage compensation of free-CaO (f-CaO) and the autoclaved hydration characteristics and environmental performance of CFB fly ash mixed cementitious materials (CMM). In this work, long-term volume stability of CMM is improved with the addition of CFBFA. These findings suggest that the compressive strength of sample CMM0.5 is the highest under both standard condition (67.21 MPa) and autoclaved condition (89.56 MPa). Meanwhile, the expansion rate (0.0207%) of sample CMM0.5 is the lowest, which proves the shrinkage compensation effect of f-CaO in CFBFA. The main hydration products of CMM0.5 are Ca2SiO4•H2O (C-S-H) gel, CaAl2Si2O7(OH)2•H2O (C-A-S-H) gel and Ca(OH)2. In addition, the high polymerization degree of [Si(Al)O4] and the densified microstructure are presented at the sample CMM0.5. The leaching results indicates that the heavy metals in CMM0.5 satisfies the WHO standards for drinking water due to physical encapsulation and charge balance. Therefore, this investigation provides a novel method of using CFB fly ash in cement.
    Type of Medium: Online Resource
    ISSN: 1996-1944
    URL: Article
    DOI: 10.3390/ma14206004
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2487261-1
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  • 8
    Online Resource
    Online Resource
    Analysis of Photo-Generated Carrier Escape in Multiple Quantum Wells
    MDPI AG ; 2023
    In:  Crystals Vol. 13, No. 5 ( 2023-05-17), p. 834-
    Details
    In: Crystals, MDPI AG, Vol. 13, No. 5 ( 2023-05-17), p. 834-
    Abstract: Recent experiments have shown that more than 85% of photo-generated carriers can escape from multiple quantum wells (MQWs) sandwiched between p-type and n-type layers (PIN). In this work, we quantitatively analyze the relationship between the energy of carriers and the height of potential barriers to be crossed, based on the GaAs/InGaAs quantum well structure system, combined with the Heisenberg uncertainty principle. It was found that that the energy obtained by electrons from photons is just enough for them to escape, and it was found that the energy obtained by the hole is just enough for it to escape due to the extra energy calculated, based on the uncertainty principle. This extra energy is considered to come from photo-generated thermal energy. The differential reflection spectrum of the structure is then measured by pump–probe technology to verify the assumption. The experiment shows that the photo-generated carrier has a longer lifetime in its short circuit (SC) state, and thus it possesses a lower structure temperature than that in open circuit (OC). This can only explain a thermal energy reduction caused by the continuous carrier escape in SC state, indicating an extra thermal energy transferred to the escaping carriers. This study is of great significance to the design of new optoelectronic devices and can improve the theory of photo-generated carrier transports.
    Type of Medium: Online Resource
    ISSN: 2073-4352
    URL: Article
    DOI: 10.3390/cryst13050834
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2661516-2
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  • 9
    Online Resource
    Online Resource
    Diffuse Reflection Effects in Visible Light Positioning: Analysis, Modeling, and Evaluation
    MDPI AG ; 2023
    In:  Electronics Vol. 12, No. 17 ( 2023-08-29), p. 3646-
    Details
    In: Electronics, MDPI AG, Vol. 12, No. 17 ( 2023-08-29), p. 3646-
    Abstract: Currently, the Global Positioning System (GPS) is widely used, but its signal is attenuated by factors such as trees, walls, and ceilings, which severely degrade its positioning accuracy. To fill the gap, various indoor positioning techniques have attracted increasing attention in recent years. Visible light positioning (VLP) is a promising scheme for indoor positioning due to its high precision, high security, and low energy consumption; however, ubiquitous diffuse reflection affects the accuracy and robustness of VLP. During our testing, we found that diffuse reflection could increase the error in RSS values by 20~30%, severely affecting VLP accuracy; however, diffuse reflection is inevitable in real positioning environments. To solve this problem, this paper first establishes a wall diffuse reflection model and then implements a visible light positioning system based on an Internet of Things platform. Finally, this paper uses the system to verify the effectiveness of the diffuse reflection model. The experiments show that the proposed model effectively improves positioning accuracy by 36.7~61.3%.
    Type of Medium: Online Resource
    ISSN: 2079-9292
    URL: Article
    DOI: 10.3390/electronics12173646
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2662127-7
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  • 10
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    Online Resource
    Transcriptome Analysis Reveals the Genes Related to Water-Melon Fruit Expansion under Low-Light Stress
    MDPI AG ; 2023
    In:  Plants Vol. 12, No. 4 ( 2023-02-18), p. 935-
    Details
    In: Plants, MDPI AG, Vol. 12, No. 4 ( 2023-02-18), p. 935-
    Abstract: Watermelon is one of people’s favorite fruits globally. Fruit size is one of the important characteristics of fruit quality. Low light can seriously affect fruit development, but there have been no reports concerning molecular mechanism analysis in watermelons involved in fruit expansion under low-light stress. To understand this mechanism, the comparative transcriptomic file of watermelon fruit flesh at four different developmental stages under different light levels was studied. The results showed that the fruit size and content of soluble sugar and amino acids at low-light stress significantly decreased compared to the control. In addition, 0–15 DAP was the rapid expansion period of watermelon fruit affected by shading. In total, 8837 differentially expressed genes (DEGs) were identified and 55 DEGs were found to play a role in the four different early fruit development stages. We also found that genes related to oxidation-reduction, secondary metabolites, carbohydrate and amino acid metabolism and transcriptional regulation played a key role in watermelon fruit expansion under low-light stress. This study provides a foundation to investigate the functions of low-light stress-responsive genes and the molecular mechanism of the effects of low-light stress on watermelon fruit expansion.
    Type of Medium: Online Resource
    ISSN: 2223-7747
    URL: Article
    DOI: 10.3390/plants12040935
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2704341-1
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