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  • 1
    In: Sensors, MDPI AG, Vol. 19, No. 7 ( 2019-04-08), p. 1667-
    Abstract: Wide Swath and High Resolution Airborne Pushbroom Hyperspectral Imager (WiSHiRaPHI) is the new-generation airborne hyperspectral imager instrument of China, aimed at acquiring accurate spectral curve of target on the ground with both high spatial resolution and high spectral resolution. The spectral sampling interval of WiSHiRaPHI is 2.4 nm and the spectral resolution is 3.5 nm (FWHM), integrating 256 channels coving from 400 nm to 1000 nm. The instrument has a 40-degree field of view (FOV), 0.125 mrad instantaneous field of view (IFOV) and can work in high spectral resolution mode, high spatial resolution mode and high sensitivity mode for different applications, which can adapt to the Velocity to Height Ratio (VHR) lower than 0.04. The integration has been finished, and several airborne flight validation experiments have been conducted. The results showed the system’s excellent performance and high efficiency.
    Type of Medium: Online Resource
    ISSN: 1424-8220
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
    detail.hit.zdb_id: 2052857-7
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  • 2
    Online Resource
    Online Resource
    MDPI AG ; 2023
    In:  Applied Sciences Vol. 13, No. 4 ( 2023-02-04), p. 2031-
    In: Applied Sciences, MDPI AG, Vol. 13, No. 4 ( 2023-02-04), p. 2031-
    Abstract: Carbon nanotubes (CNTs) have wide-ranging applications due to their excellent mechanical and electrical properties. However, there is little research on the nonlinear mechanical properties of thermal-electro-mechanical coupling. In this paper, we study the nonlinear vibrations of CNTs by a thermal-electro-mechanical coupling beam theory. The Galerkin method is used to discretize the partial differential equation and obtain two nonlinear ordinary differential equations that describe the first- and second-order mode vibrations. Then, we obtain the approximate analytical solutions of the two equations for the primary resonance and the subharmonic resonance using the multi-scale method. The results indicate the following three points. Firstly, the temperature and electric fields have a significant influence on the first-mode vibration, while they have little influence on the second-mode vibration. Under the primary resonance, when the load amplitude of the second mode is 20 times that of the first mode, the maximal vibrational amplitude of the second is only one-fifth of the first. Under the subharmonic resonance, it is more difficult to excite the subharmonic vibration at the second-order mode than that of the first mode for the same parameters. Secondly, because the coefficient of electrical expansion (CEE) is much bigger than the coefficient of thermal expansion (CTE), CNTs are more sensitive to changes in the electric field than the temperature field. Finally, under the primary resonance, there are two bifurcation points in the frequency response curves and the load-amplitude curves. As a result, they will induce the jump phenomenon of vibrational amplitude. When the subharmonic vibration is excited, the free vibration term does not disappear, and the steady-state vibration includes two compositions.
    Type of Medium: Online Resource
    ISSN: 2076-3417
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2704225-X
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  • 3
    Online Resource
    Online Resource
    MDPI AG ; 2023
    In:  Applied Sciences Vol. 13, No. 9 ( 2023-05-04), p. 5659-
    In: Applied Sciences, MDPI AG, Vol. 13, No. 9 ( 2023-05-04), p. 5659-
    Abstract: Structural health monitoring systems continuously monitor the operational state of structures, generating a large amount of monitoring data during the process. The structural responses of extreme events, such as earthquakes, ship collisions, or typhoons, could be captured and further analyzed. However, it is challenging to identify these extreme events due to the interference of faulty data. Real-world monitoring systems suffer from frequent misidentification and false alarms. Unfortunately, it is difficult to improve the system’s built-in algorithms, especially the deep neural networks, partly because the current neural networks only output results and do not provide an interpretable decision-making basis. In this study, a deep learning-based method with visual interpretability is proposed to identify seismic data under sensor faults interference. The transfer learning technique is employed to learn the features of seismic data and faulty data with efficiency. A post hoc interpretation algorithm, termed Gradient-weighted Class Activation Mapping (Grad-CAM), is embedded into the neural networks to uncover the interest regions that support the output decision. The in situ seismic responses of a cable-stayed long-span bridge are used for method verification. The results show that the proposed method can effectively identify seismic data mixed with various types of faulty data while providing good interpretability.
    Type of Medium: Online Resource
    ISSN: 2076-3417
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2704225-X
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  • 4
    Online Resource
    Online Resource
    MDPI AG ; 2023
    In:  Mathematics Vol. 11, No. 19 ( 2023-10-03), p. 4156-
    In: Mathematics, MDPI AG, Vol. 11, No. 19 ( 2023-10-03), p. 4156-
    Abstract: Medical comparative studies often involve collecting data from paired organs, which can produce either bilateral or unilateral data. While many testing procedures are available that account for the intra-class correlation between paired organs for bilateral data, more research needs to be conducted to determine how to analyze combined correlated bilateral and unilateral data. In practice, stratification is often used in analysis to ensure participants are allocated equally to each experimental condition. In this paper, we propose three Maximum Likelihood Estimation (MLE)-based methods for testing the homogeneity of differences between two proportions for stratified bilateral and unilateral data across strata using Donner’s model. We compare the performance of these methods with a model-based method based on Generalized Estimating Equations using Monte Carlo simulations. We also provide a real example to illustrate the proposed methodologies. Our findings suggest that the Score test performs well and offers a valuable alternative to the exact tests in future studies.
    Type of Medium: Online Resource
    ISSN: 2227-7390
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2704244-3
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  • 5
    In: Marine Drugs, MDPI AG, Vol. 19, No. 11 ( 2021-10-20), p. 588-
    Abstract: Pancreatic ductal adenocarcinoma (PDAC) is a devastating digestive system carcinoma with high incidence and death rates. PDAC cells are dependent on the Gln metabolism, which can preferentially utilize glutamic oxaloacetate transaminase 1 (GOT1) to maintain the redox homeostasis of cancer cells. Therefore, small molecule inhibitors targeting GOT1 can be used as a new strategy for developing cancer therapies. In this study, 18 butyrolactone derivatives (1–18) were isolated from a marine-derived Aspergillus terreus, and asperteretone B (5), aspulvinone H (AH, 6), and (+)-3′,3′-di-(dimethylallyl)-butyrolactone II (12) were discovered to possess significant GOT1-inhibitory activities in vitro, with IC50 values of (19.16 ± 0.15), (5.91 ± 0.04), and (26.38 ± 0.1) µM, respectively. Significantly, the molecular mechanism of the crystal structure of GOT1–AH was elucidated, wherein AH and the cofactor pyrido-aldehyde 5-phosphate competitively bound to the active sites of GOT1. More importantly, although the crystal structure of GOT1 has been discovered, the complex structure of GOT1 and its inhibitors has never been obtained, and the crystal structure of GOT1–AH is the first reported complex structure of GOT1/inhibitor. Further in vitro biological study indicated that AH could suppress glutamine metabolism, making PDAC cells sensitive to oxidative stress and inhibiting cell proliferation. More significantly, AH exhibited potent in vivo antitumor activity in an SW1990-cell-induced xenograft model. These findings suggest that AH could be considered as a promising lead molecule for the development of anti-PDAC agents.
    Type of Medium: Online Resource
    ISSN: 1660-3397
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2175190-0
    SSG: 15,3
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  • 6
    Online Resource
    Online Resource
    MDPI AG ; 2022
    In:  Remote Sensing Vol. 14, No. 7 ( 2022-03-23), p. 1554-
    In: Remote Sensing, MDPI AG, Vol. 14, No. 7 ( 2022-03-23), p. 1554-
    Abstract: The lidar ratio (LR) is a key parameter for the retrieval of atmospheric optical parameters from lidar equations. In this study, we simulated the optical parameters to investigate the impact factors of the LR using a three-component optical aerosol assumption based on the Mie model. The simulated LR was generally related to the overall particle size of the aerosols, the proportion of elemental carbon (EC), as well as aerosol mixing states and hygroscopicity. The LR was positively correlated with the particle size and volume fraction of elemental carbon (fEC). The LR increased more than three-fold with the increase in fEC from 0% to 40%. The LR of the core-shell (CS) mixing state and homogeneously internal (INT) mixing state was greater than that of the external (EXT) mixing state. The LR of all mixing states increased monotonically with hygroscopicity when the fEC was below 10%, while the LR of the core-shell mixing state (homogeneously internal mixing state) initially decreased (increased) and then increased (decreased) with increasing hygroscopicity when the fEC was more than 20%. These results will help in selecting a reasonable LR for practical applications.
    Type of Medium: Online Resource
    ISSN: 2072-4292
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2513863-7
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  • 7
    In: Water, MDPI AG, Vol. 15, No. 2 ( 2023-01-14), p. 351-
    Abstract: Eutrophication and global warming boost the outbreak of cyanobacterial blooms and the spread of invasive cyanobacterial species such as Chrysosporum ovalisporum. Different from the often steady-state conditions under laboratory cultivation, the external input of nutrients in natural water is often intermittent and pulsed, which may affect the response of cyanobacteria. In this study, we cultured C. ovalisporum under two phosphorus treatment patterns: a one-time treatment and a five-time pulsed treatment with the same total dosing. Our results showed that phosphorus deficiency in the water inhibits the growth of C. ovalisporum, thereby significantly reducing its biomass and photosynthetic activity (p 〈 0.05). In addition, phosphorus deficiency led C. ovalisporum to secrete more exopolysaccharides and alkaline phosphatase. Compared with the one-time treatment, the multiple pulses promoted the absorption of phosphorus by C. ovalisporum and inhibited the synthesis of alkaline phosphatase but had no significant effect on the release of cylindrospermopsin (CYN). We also found that multiple pulses had a more significant growth-promoting effect on C. ovalisporum under low phosphorus concentrations. Our results indicated the overall strong adaptability of C. ovalisporum to dynamic changes in phosphate levels in the water column and provide new insight into the outbreak and dispersal strategies of C. ovalisporum.
    Type of Medium: Online Resource
    ISSN: 2073-4441
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2521238-2
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  • 8
    Online Resource
    Online Resource
    MDPI AG ; 2022
    In:  Symmetry Vol. 14, No. 10 ( 2022-10-13), p. 2130-
    In: Symmetry, MDPI AG, Vol. 14, No. 10 ( 2022-10-13), p. 2130-
    Abstract: The magnetic sensor should acquire a high detection ability over a wide low-frequency (LF) band of 1–100 Hz for biomagnetic measurements due to the large LF noise. This work presents a magnetic sensor with a modulation coil based on the tri-layer symmetrical Metglas/Quartz/Metglas laminate for LF magnetic fields detection. The Metglas/Quartz/Metglas laminate was fabricated using a rectangle quartz plate with twenty Metglas foils epoxy glued symmetrically. Additionally, the coil can be used to generate modulation voltage. The limit of detection (LOD) of the fabricated symmetrical magnetoelectric (ME) sensor has been measured and optimized without DC bias via frequency modulation technique. Experimental results demonstrate that the proposed ME sensor can detect a small magnetic field of 11 pT at 1 Hz. Moreover, the Metglas thickness and the modulation voltage also have been optimized and the detection ability of the fabricated sensor has been enhanced with a lower LOD value of 2.7 pT at 1 Hz. This paper provides a symmetrical magnetoelectric sensor using piezoelectric quartz material for LF pico-Tesla magnetic field signals detection. Additionally, the symmetrical sensor without bias can provide a cost-effective and high-performance approach for LF magnetic field detection.
    Type of Medium: Online Resource
    ISSN: 2073-8994
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2518382-5
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  • 9
    In: Processes, MDPI AG, Vol. 7, No. 6 ( 2019-06-01), p. 328-
    Abstract: As the largest global renewable source, hydropower is a useful supplement to mountainous distribution networks with abundant water resources, and shoulders a large portion of the regulation duty in many power systems. In particular, in the form of decentralized energy sources located to their customers, small hydropower (SHP) improve grid stability by diversifying the electricity system and reducing power loss. The mountainous distribution networks supplied by small hydropower are closed-loop design but open-loop operation, which easily causes the tripping of tie line even further the off-grid operation of small hydropower system. Once the tie line trips, the current countermeasures—such as hydropower shutdown and load shedding—do not fully guarantee the reliability of power supply and the utilization efficiency of hydropower. This paper studies the amplitude-frequency characteristics of SHP off-grid, according to the typical integration of hydropower in South China, a SHP on-grid/off-grid model is established based on the Power Systems Computer Aided Design (PSCAD) platform. It is found that due to the inertia of SHP, the amplitude-frequency characteristics of SHP island system are relatively slow, and the process of non-synchronization with the main grid is gradually expanded. The characteristic of SHP has a certain degree of synchronization with the main grid in the initial island operates stage, which helps to find a novel grid connection method. This paper further proposes the strategy of using fast busbar automatic transfer switch (BATS), which quickly connect the trip-off SHP to the distribution network under the condition of permitting distributed energy grid-connected. The PSCAD simulation results show that proposed strategy has a limited impact on the power grid and prove the effectiveness of the method.
    Type of Medium: Online Resource
    ISSN: 2227-9717
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
    detail.hit.zdb_id: 2720994-5
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  • 10
    In: Metals, MDPI AG, Vol. 13, No. 4 ( 2023-04-17), p. 791-
    Abstract: In this study, open-cell copper foam with completely interconnected sphere pores was prepared by a modified sintering–dissolution process using a preformed calcium chloride template skeleton as space holder. Compared with the traditional foaming process method, the open-cell copper foam prepared by this method has fewer impurities and better surface morphology. In addition, the pore distribution can be controlled by adjusting the distribution of calcium chloride particles in the skeleton. The compression performance, airflow resistance, and filtration performance of the prepared open-cell copper foam were studied. The results show that with the increase in porosity, the bearing capacity of open-cell copper foam decreases, but the width of the stress platform increases. The prepared open-cell copper foam exhibits excellent energy absorption efficiency, reaching nearly 90% at a porosity of 85%. When the porosity is 85%, the static airflow resistance of the structure is as high as 9 KPa·s·m−2. Moreover, the structure has a filtration efficiency of more than 90% as the filtration thickness exceeds 20 mm, which demonstrates the excellent filtration ability. Such open-cell copper foam shows multi-functional potential as an impact damper, sound absorber, and impurity filter.
    Type of Medium: Online Resource
    ISSN: 2075-4701
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2662252-X
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