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  • 1
    Online Resource
    Online Resource
    LACE: Low-Cost Access Control Based on Edge Computing for Smart Buildings
    MDPI AG ; 2023
    In:  Electronics Vol. 12, No. 2 ( 2023-01-13), p. 412-
    Details
    In: Electronics, MDPI AG, Vol. 12, No. 2 ( 2023-01-13), p. 412-
    Abstract: With the explosive growth in personal mobile devices, offloading computation through nearby mobile user devices as opportunistic edge servers to support complex applications with limited computation resources is receiving increasing attention. In this paper, we first establish the optimal opportunistic offloading problem using the statistical properties of user movement speed and CPU load of mobile edge servers. We then determine the amount of computation to be offloaded to individual mobile edge servers. Moreover, we design an adaptive mechanism based on PID to realize the function of continuing large data packets from breakpoints, mainly used to adjust the size of data packets automatically. It efficiently avoids data loss and reduces the cost of resources through the latency deviation as the variable of the gain function to estimate the packet size. Finally, an access control system based on edge computing is designed and developed to make full use of the mobile phones of nearby users. It can address the shortcomings of traditional schemes with high latency to some extent, and it makes latency lower and data reliability higher.
    Type of Medium: Online Resource
    ISSN: 2079-9292
    URL: Article
    DOI: 10.3390/electronics12020412
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2662127-7
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  • 2
    Online Resource
    Online Resource
    Optimized Scheme for Accelerating the Slagging Reaction and Slag–Metal–Gas Emulsification in a Basic Oxygen Furnace
    MDPI AG ; 2020
    In:  Applied Sciences Vol. 10, No. 15 ( 2020-07-24), p. 5101-
    Details
    In: Applied Sciences, MDPI AG, Vol. 10, No. 15 ( 2020-07-24), p. 5101-
    Abstract: Basic oxygen furnace (BOF) steelmaking is widely used in the metallurgy field. The slagging reaction is a necessary process that oxidizes C, Mn, Si, P, S, and other impurities and therefore directly affects the quality of the resultant steel. Relevant research has suggested that intensifying the stirring effect can accelerate the slagging reaction and that the dynamic characteristics of the top blow are the key factor in exploring the related complex physical and chemical phenomena. To address the issue, the standard k-ω turbulence model and level-set method were adopted in the present work and a fluid dynamics model was developed for a BOF. Accordingly, the slag–metal–gas emulsion interaction and stirring effect were investigated, and the interference mechanism of a multi-nozzle supersonic coherent jet was revealed. Finally, a self-adjustment method based on fuzzy control is proposed for the oxygen lance. The results indicate that the transfer efficiency of jet kinetic energy at the gas–liquid interface is the critical factor for the slagging reaction and that multi-nozzle oxygen lances with a certain twisted angle have important advantages with respect to stirring effects and splashing inhibition. The fuzzy control method predicts that the optimal nozzle twist angle is within the range of 7.2° to 7.8°. The results presented herein can provide theoretical support and beneficial reference information for BOF steelmaking.
    Type of Medium: Online Resource
    ISSN: 2076-3417
    URL: Article
    DOI: 10.3390/app10155101
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2704225-X
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  • 3
    Online Resource
    Online Resource
    Fabrication and Characterization of Seawater Temperature Sensor with Self-Calibration Based on Optical Microfiber Coupler Interferometer
    MDPI AG ; 2020
    In:  Applied Sciences Vol. 10, No. 17 ( 2020-08-31), p. 6018-
    Details
    In: Applied Sciences, MDPI AG, Vol. 10, No. 17 ( 2020-08-31), p. 6018-
    Abstract: In this paper, a novel high-sensitivity temperature sensor with two sensing regions based on optical microfiber coupler interferometer (OMCI) for ocean application is proposed. The OMCI sensor is constructed by connecting Faraday mirrors to the two ports of the microfiber coupler respectively. Its sensing characteristics analysis and experimental test are conducted. Using a broad-spectrum light source as input light, temperature sensor demodulation can be implemented by tracking the drift of the characteristic wavelength (dip wavelength or peak wavelength) of the reflection spectrum. Experimental results show that the temperature sensitivity of the OMCI sensor can reach 1007.4 pm/°C and the detection dynamic range up to 17.6 °C. Besides, due to the two sensing regions in OMCI, self-calibration of seawater temperature sensing and optimization of multi-parameter cross-sensitive demodulation are performed by affecting the non-equal-arm interferometer through a specific package design of the external environment. The sensor has the advantages of high sensitivity, large dynamic range, small size, easy to manufacture, which will play an important role in the practical application of marine environment monitoring.
    Type of Medium: Online Resource
    ISSN: 2076-3417
    URL: Article
    DOI: 10.3390/app10176018
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2704225-X
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  • 4
    Online Resource
    Online Resource
    RAC-GAN-Based Scenario Generation for Newly Built Wind Farm
    MDPI AG ; 2023
    In:  Energies Vol. 16, No. 5 ( 2023-03-03), p. 2447-
    Details
    In: Energies, MDPI AG, Vol. 16, No. 5 ( 2023-03-03), p. 2447-
    Abstract: Due to the lack of historical output data of new wind farms, there are difficulties in the scheduling and planning of power grid and wind power output scenario generation. The randomness and uncertainty of meteorological factors lead to the results of traditional scenario generation methods not having the ability to accurately reflect their uncertainty. This article proposes a RAC-GAN-based scenario generation method for a new wind farm output. First, the Pearson coefficient is adopted in this method to screen the meteorological factors and obtain the ones that have larger impact on wind power output; Second, based on the obtained meteorological factors, the Grey Relation Analysis (GRA) is used to analyze the meteorological correlation between multiple wind farms with sufficient output data and new wind farms (target power stations), so that the wind farm with high meteorological correlation is selected as the source power station. Then, the K-means method is adopted to cluster the meteorological data of the source power station, thus generating the target power station scenario in which the cluster information serves as the label of the robust auxiliary classifier generative adversarial network (RAC-GAN) model and the output data of the source power station is considered as the basis. Finally, the actual wind farm output and meteorological data of a region in northeast China are employed for arithmetic analysis to verify the effectiveness of the proposed method. It is proved that the proposed method can effectively reflect the characteristics of wind power output and solve the problem of insufficient historical data of new wind farm output.
    Type of Medium: Online Resource
    ISSN: 1996-1073
    URL: Article
    DOI: 10.3390/en16052447
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2437446-5
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  • 5
    Online Resource
    Online Resource
    Geospatial Distributions of Groundwater Quality in Gedaref State Using Geographic Information System (GIS) and Drinking Water Quality Index (DWQI)
    MDPI AG ; 2019
    In:  International Journal of Environmental Research and Public Health Vol. 16, No. 5 ( 2019-02-28), p. 731-
    Details
    In: International Journal of Environmental Research and Public Health, MDPI AG, Vol. 16, No. 5 ( 2019-02-28), p. 731-
    Abstract: The observation of groundwater quality elements is essential for understanding the classification and distribution of drinking water. Geographic Information System (GIS) and remote sensing (RS), are intensive tools for the performance and analysis of spatial datum associated with groundwater sources control. In this study, groundwater quality parameters were observed in three different aquifers including: sandstone, alluvium and basalt. These aquifers are the primary source of national drinking water and partly for agricultural activity in El Faw, El Raha (Fw-Rh), El Qalabat and El Quresha (Qa-Qu) localities in the southern part of Gedaref State in eastern Sudan. The aquifers have been overworked intensively as the main source of indigenous water supply in the study area. The interpolation methods were used to demonstrate the facies pattern and Drinking Water Quality Index (DWQI) of the groundwater in the research area. The GIS interpolation tool was used to obtain the spatial distribution of groundwater quality parameters and DWQI in the area. Forty samples were assembled and investigated for the analysis of major cations and anions. The groundwater in this research is controlled by sodium and bicarbonate ions that defined the composition of the water type to be Na HCO3. However, from the plots of piper diagram; the samples result revealed (40%) Na-Mg-HCO3 and (35%) Na-HCO3 water types. The outcome of the analysis reveals that several groundwater samples have been found to be suitable for drinking purposes in Fa-Rh and Qa-Qu areas.
    Type of Medium: Online Resource
    ISSN: 1660-4601
    URL: Article
    DOI: 10.3390/ijerph16050731
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
    detail.hit.zdb_id: 2175195-X
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  • 6
    Online Resource
    Online Resource
    Event-Triggered Finite-Time Formation Control of Underactuated Multiple ASVs with Prescribed Performance and Collision Avoidance
    MDPI AG ; 2023
    In:  Sensors Vol. 23, No. 15 ( 2023-07-28), p. 6756-
    Details
    In: Sensors, MDPI AG, Vol. 23, No. 15 ( 2023-07-28), p. 6756-
    Abstract: In this paper, an event-triggered finite-time controller is proposed for solving the formation control problems of underactuated multiple autonomous surface vessels (ASVs), including asymmetric mass matrix, collision avoidance, maintaining communication distances and prescribed performance. First, to not only avoid collisions between the follower and leader but also maintain an effective communication distance, a desired tracking distance is designed to be maintained. Second, an improved barrier Lyapunov function (BLF) is proposed to implement the tracking error constraint. In addition, the relative threshold event-triggering strategy effectively solves the communication pressure problem and greatly saves communication resources. Finally, based on coordinate transformation, line of sight (LOS) and dynamic surface control (DSC), a comprehensive finite-time formation control method is proposed to avoid collisions and maintain communication distance. All the signals of the proposed control system can be stabilized in finite time (PFS). The numerical simulation results verify the effectiveness of the proposed control system.
    Type of Medium: Online Resource
    ISSN: 1424-8220
    URL: Article
    DOI: 10.3390/s23156756
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2052857-7
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  • 7
    Online Resource
    Online Resource
    Study on the Effects of the Wear-Rings Clearance on the Solid-Liquid Two-Phase Flow Characteristics of Centrifugal Pumps
    MDPI AG ; 2020
    In:  Symmetry Vol. 12, No. 12 ( 2020-12-04), p. 2003-
    Details
    In: Symmetry, MDPI AG, Vol. 12, No. 12 ( 2020-12-04), p. 2003-
    Abstract: In order to study the wear law of the centrifugal pump flowing surface under different wear-rings clearance, the McLaury wear model was used to conduct the full-passage numerical simulation of solid-liquid two-phase flow in a single-stage single-suction centrifugal pump. The reliability of the numerical calculation method is verified by comparing the experimental data and numerical simulation results. The clearance is 0.1, 0.15, 0.2, 0.3 and 0.5 mm, respectively. The results show that the wear of the centrifugal pump blades is mainly concentrated in the end part and the inlet part of the blade, and the wear of the pressure surface at the end of the suction surface and the front of the blade is more serious. As the clearance increases, the maximum wear value in the impeller increases first and then decreases, reaching a maximum at 0.15 mm. With the increase of the clearance, the wear degree and the wear rate of the volute wall surface first increase and then decrease, and reach the maximum at 0.2 mm. With the increase of the clearance and the concentration of the fluid medium, the wear at the clearance of the centrifugal pump is more serious, and the severe wear area exhibits a point-like circumferential distribution.
    Type of Medium: Online Resource
    ISSN: 2073-8994
    URL: Article
    DOI: 10.3390/sym12122003
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2518382-5
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  • 8
    Online Resource
    Online Resource
    Design and Experimental Study of Ball-Head Cone-Tail Injection Mixer Based on Computational Fluid Dynamics
    MDPI AG ; 2023
    In:  Agriculture Vol. 13, No. 7 ( 2023-07-11), p. 1377-
    Details
    In: Agriculture, MDPI AG, Vol. 13, No. 7 ( 2023-07-11), p. 1377-
    Abstract: The uniform and accurate mixing of pesticides in water is a necessary prerequisite for plant protection, especially for enabling precise variable spraying, and is also an important method to achieve a precise reduction in pesticide spraying. In order to ensure the uniform mixing of pesticides and water and solve the problems of traditional injection mixers, such as the limited range in the mixing ratio and unadjustable proportion, an active injection liquid mixer is designed in this paper. The mixer can be matched with an online mixing and spraying device to achieve accuracy in mixing and spraying. In this paper, a computational fluid dynamics (CFD) method is used to optimize the structure of the mixer. Through comparative analysis, the optimal structure of the mixer was found. It has a spherical head and conical tail, the number of guide plates is seven, and the shape is semicircular. By calculating the volume fraction of pesticide distribution under different cross-sections, the coefficient of variation in the process of mixing is obtained. The analysis shows that the maximum coefficient of variation of the ball-head cone-tail active injection mixer was 2.88% (lower than the allowable 5%) with a mixing ratio ranging from 300:1 to 3000:1. At the same time, image analysis methods of high-definition photography and ultraviolet spectrophotometry were used to analyze the mixing effect of the mixer. The test results show that, when the pressure of the pesticide injection is 1 MPa, the distribution of the pesticide and water in the ball-head cone-tail injection mixer is more uniform under different mixing ratios, and it has a better spatio-temporal distribution uniformity with the concentration changing a little at different times and different spatial locations. The mixer can provide a theoretical reference and technical support for the subsequent realization of an accurate online variable spray.
    Type of Medium: Online Resource
    ISSN: 2077-0472
    URL: Article
    DOI: 10.3390/agriculture13071377
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2651678-0
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  • 9
    Online Resource
    Online Resource
    Prediction and Experimental Study of Tire Slip Rate Based on Chassis Sinkage Amount
    MDPI AG ; 2023
    In:  Agriculture Vol. 13, No. 3 ( 2023-03-13), p. 665-
    Details
    In: Agriculture, MDPI AG, Vol. 13, No. 3 ( 2023-03-13), p. 665-
    Abstract: In view of the problems that the fuselage inclines and the driving straightness is difficult to guarantee due to the sinking and sliding of the wheels when the high-clearance plant protection machine is working in the paddy field, this paper takes high-clearance wheels as the research object, based on the paddy field driving environment, establishes a prediction model of the wheel subsidence through derivation, and explores the influence of different wheel parameters on the subsidence characteristics through experiments, so as to improve the chassis trafficability. At the same time, using the test data under different wheel parameters, the prediction model of the settlement of the working chassis with high clearance is correspondingly modified. Finally, the paddy field trafficability of the working chassis is compared and analyzed based on different tire parameters. The results show that when the wheel slip rate is 0.5, the traction force of the solid tire is 37% higher than that of the pneumatic tire; when the height of the wheel spike increases, the traction force increases, and the settlement decreases obviously; proper increase of the wheel diameter can improve the passing performance of the chassis; with the increase of the tire width, the angle of soil penetration decreases while the tire is driving, and the angle of the slope climbing increases; and when the load changes, the driving coefficient is proportional to the traction coefficient, and the tire resistance coefficient is inversely proportional to the traction coefficient. Through the research on the settlement mechanism of the high-clearance operation chassis and the analysis of the paddy field trafficability, the stability of the high-clearance plant protection machine in the paddy field has been improved, providing a platform and guarantee for subsequent precision operation.
    Type of Medium: Online Resource
    ISSN: 2077-0472
    URL: Article
    DOI: 10.3390/agriculture13030665
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2651678-0
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  • 10
    Online Resource
    Online Resource
    Biomedical Potential of Ultrafine Ag Nanoparticles Coated on Poly (Gamma-Glutamic Acid) Hydrogel with Special Reference to Wound Healing
    MDPI AG ; 2018
    In:  Nanomaterials Vol. 8, No. 5 ( 2018-05-14), p. 324-
    Details
    In: Nanomaterials, MDPI AG, Vol. 8, No. 5 ( 2018-05-14), p. 324-
    Type of Medium: Online Resource
    ISSN: 2079-4991
    URL: Article
    DOI: 10.3390/nano8050324
    Language: English
    Publisher: MDPI AG
    Publication Date: 2018
    detail.hit.zdb_id: 2662255-5
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