Characterizing Evaporation Ducts Within the Marine Atmospheric Boundary Layer Using Artificial Neural Networks

We apply a multilayer perceptron machine learning (ML) regression approach to infer electromagnetic (EM) duct heights within the marine atmospheric boundary layer (MABL) using sparsely sampled EM propagation data obtained within a bistatic context. This paper explains the rationale behind the selection of the ML network architecture, along with other model hyperparameters, in an effort to demystify the process of arriving at a useful ML model. The resulting speed of our ML predictions of EM duct heights, using sparse data measurements within MABL, indicates the suitability of the proposed method for real-time applications.Comment: 13 pages, 7 figure

Hybrid Satellite-Terrestrial Communication Networks for the Maritime Internet of Things: Key Technologies, Opportunities, and Challenges

With the rapid development of marine activities, there has been an increasing number of maritime mobile terminals, as well as a growing demand for high-speed and ultra-reliable maritime communications to keep them connected. Traditionally, the maritime Internet of Things (IoT) is enabled by maritime satellites. However, satellites are seriously restricted by their high latency and relatively low data rate. As an alternative, shore & island-based base stations (BSs) can be built to extend the coverage of terrestrial networks using fourth-generation (4G), fifth-generation (5G), and beyond 5G services. Unmanned aerial vehicles can also be exploited to serve as aerial maritime BSs. Despite of all these approaches, there are still open issues for an efficient maritime communication network (MCN). For example, due to the complicated electromagnetic propagation environment, the limited geometrically available BS sites, and rigorous service demands from mission-critical applications, conventional communication and networking theories and methods should be tailored for maritime scenarios. Towards this end, we provide a survey on the demand for maritime communications, the state-of-the-art MCNs, and key technologies for enhancing transmission efficiency, extending network coverage, and provisioning maritime-specific services. Future challenges in developing an environment-aware, service-driven, and integrated satellite-air-ground MCN to be smart enough to utilize external auxiliary information, e.g., sea state and atmosphere conditions, are also discussed

An artificial neural network predictor for tropospheric surface duct phenomena

International audienceIn this work, an artificial neural network (ANN) model is developed and used to predict the presence of ducting phenomena for a specific time, taking into account ground values of atmospheric pressure, relative humidity and temperature. A feed forward backpropagation ANN is implemented, which is trained, validated and tested using atmospheric radiosonde data from the Helliniko airport, for the period from 1991 to 2004. The network's quality and generality is assessed using the Area Under the Receiver Operating Characteristics (ROC) Curves (AUC), which resulted to a mean value of about 0.86 to 0.90, depending on the observation time. In order to validate the ANN results and to evaluate any further improvement options of the proposed method, the problem was additionally treated using Least Squares Support Vector Machine (LS-SVM) classifiers, trained and tested with identical data sets for direct performance comparison with the ANN. Furthermore, time series prediction and the effect of surface wind to the presence of tropospheric ducts appearance are discussed. The results show that the ANN model presented here performs efficiently and gives successful tropospheric ducts predictions

Optimization of Natural Ventilation Design in Hot and Humid Climates Using Building Energy Simulation

This research aims to propose and explore natural ventilation schemes for the design of high-performance, non-residential buildings in hot and humid climates. Three such schemes were applied toward retrofitting the existing Hawai‘i Institute of Geophysics buildings on University of Hawai‘i at Mānoa (UHM) campus in Honolulu. The results were investigated by using parametric study and Airflow Network (AN) model, coupled with thermal model in EnergyPlus. Meanwhile, the number of discomfort hours, during the time the buildings are occupied and based on the adaptive thermal comfort, was used as a quantitative index for the performance of the natural ventilation design schemes. The results revealed that pure cross-ventilation is not a feasible mode to deliver adequate thermal comfort to the occupants, per an acceptable number of discomfort hours. However, with the supplementation of vertical ventilation ducts (shafts), the performance of natural ventilation design schemes significantly improved. In these cases, it was found that either ventilation ducts or ventilation windows can be completely closed, thus eliminating the need of one or the other in natural ventilation designs and therefore mitigating the potential for outdoor noise traveling into spaces through ventilation ducts and/or ventilation windows’ openings. This research presents my preliminary investigation toward finding the optimal scheme for natural ventilation design. After the scheme is chosen, the actual geometry of the ventilation ducts and ventilation windows, appropriate louvers and duct fittings, as well as their optimal aspect ratios, should be taken into consideration. For future research to be able to extend to incorporate a wider range of climate conditions, a hybrid ventilation approach integrating both mechanical and natural ventilation should be carried out. Moreover, further study of ventilation effectiveness, as per Computational Fluid Dynamics (CFD), is also recommended.This research aims to propose and explore natural ventilation schemes for the design of high-performance, non-residential buildings in hot and humid climates. Three such schemes were applied toward retrofitting the existing Hawai‘i Institute of Geophysics buildings on University of Hawai‘i at Mānoa (UHM) campus in Honolulu. The results were investigated by using parametric study and Airflow Network (AN) model, coupled with thermal model in EnergyPlus. Meanwhile, the number of discomfort hours, during the time the buildings are occupied and based on the adaptive thermal comfort, was used as a quantitative index for the performance of the natural ventilation design schemes. The results revealed that pure cross-ventilation is not a feasible mode to deliver adequate thermal comfort to the occupants, per an acceptable number of discomfort hours. However, with the supplementation of vertical ventilation ducts (shafts), the performance of natural ventilation design schemes significantly improved. In these cases, it was found that either ventilation ducts or ventilation windows can be completely closed, thus eliminating the need of one or the other in natural ventilation designs and therefore mitigating the potential for outdoor noise traveling into spaces through ventilation ducts and/or ventilation windows’ openings. This research presents my preliminary investigation toward finding the optimal scheme for natural ventilation design. After the scheme is chosen, the actual geometry of the ventilation ducts and ventilation windows, appropriate louvers and duct fittings, as well as their optimal aspect ratios, should be taken into consideration. For future research to be able to extend to incorporate a wider range of climate conditions, a hybrid ventilation approach integrating both mechanical and natural ventilation should be carried out. Moreover, further study of ventilation effectiveness, as per Computational Fluid Dynamics (CFD), is also recommended.This research aims to propose and explore natural ventilation schemes for the design of high-performance, non-residential buildings in hot and humid climates. Three such schemes were applied toward retrofitting the existing Hawai‘i Institute of Geophysics buildings on University of Hawai‘i at Mānoa (UHM) campus in Honolulu. The results were investigated by using parametric study and Airflow Network (AN) model, coupled with thermal model in EnergyPlus. Meanwhile, the number of discomfort hours, during the time the buildings are occupied and based on the adaptive thermal comfort, was used as a quantitative index for the performance of the natural ventilation design schemes. The results revealed that pure cross-ventilation is not a feasible mode to deliver adequate thermal comfort to the occupants, per an acceptable number of discomfort hours. However, with the supplementation of vertical ventilation ducts (shafts), the performance of natural ventilation design schemes significantly improved. In these cases, it was found that either ventilation ducts or ventilation windows can be completely closed, thus eliminating the need of one or the other in natural ventilation designs and therefore mitigating the potential for outdoor noise traveling into spaces through ventilation ducts and/or ventilation windows’ openings. This research presents my preliminary investigation toward finding the optimal scheme for natural ventilation design. After the scheme is chosen, the actual geometry of the ventilation ducts and ventilation windows, appropriate louvers and duct fittings, as well as their optimal aspect ratios, should be taken into consideration. For future research to be able to extend to incorporate a wider range of climate conditions, a hybrid ventilation approach integrating both mechanical and natural ventilation should be carried out. Moreover, further study of ventilation effectiveness, as per Computational Fluid Dynamics (CFD), is also recommended.This research aims to propose and explore natural ventilation schemes for the design of high-performance, non-residential buildings in hot and humid climates. Three such schemes were applied toward retrofitting the existing Hawai‘i Institute of Geophysics buildings on University of Hawai‘i at Mānoa (UHM) campus in Honolulu. The results were investigated by using parametric study and Airflow Network (AN) model, coupled with thermal model in EnergyPlus. Meanwhile, the number of discomfort hours, during the time the buildings are occupied and based on the adaptive thermal comfort, was used as a quantitative index for the performance of the natural ventilation design schemes. The results revealed that pure cross-ventilation is not a feasible mode to deliver adequate thermal comfort to the occupants, per an acceptable number of discomfort hours. However, with the supplementation of vertical ventilation ducts (shafts), the performance of natural ventilation design schemes significantly improved. In these cases, it was found that either ventilation ducts or ventilation windows can be completely closed, thus eliminating the need of one or the other in natural ventilation designs and therefore mitigating the potential for outdoor noise traveling into spaces through ventilation ducts and/or ventilation windows’ openings. This research presents my preliminary investigation toward finding the optimal scheme for natural ventilation design. After the scheme is chosen, the actual geometry of the ventilation ducts and ventilation windows, appropriate louvers and duct fittings, as well as their optimal aspect ratios, should be taken into consideration. For future research to be able to extend to incorporate a wider range of climate conditions, a hybrid ventilation approach integrating both mechanical and natural ventilation should be carried out. Moreover, further study of ventilation effectiveness, as per Computational Fluid Dynamics (CFD), is also recommended.This research aims to propose and explore natural ventilation schemes for the design of high-performance, non-residential buildings in hot and humid climates. Three such schemes were applied toward retrofitting the existing Hawai‘i Institute of Geophysics buildings on University of Hawai‘i at Mānoa (UHM) campus in Honolulu. The results were investigated by using parametric study and Airflow Network (AN) model, coupled with thermal model in EnergyPlus. Meanwhile, the number of discomfort hours, during the time the buildings are occupied and based on the adaptive thermal comfort, was used as a quantitative index for the performance of the natural ventilation design schemes. The results revealed that pure cross-ventilation is not a feasible mode to deliver adequate thermal comfort to the occupants, per an acceptable number of discomfort hours. However, with the supplementation of vertical ventilation ducts (shafts), the performance of natural ventilation design schemes significantly improved. In these cases, it was found that either ventilation ducts or ventilation windows can be completely closed, thus eliminating the need of one or the other in natural ventilation designs and therefore mitigating the potential for outdoor noise traveling into spaces through ventilation ducts and/or ventilation windows’ openings. This research presents my preliminary investigation toward finding the optimal scheme for natural ventilation design. After the scheme is chosen, the actual geometry of the ventilation ducts and ventilation windows, appropriate louvers and duct fittings, as well as their optimal aspect ratios, should be taken into consideration. For future research to be able to extend to incorporate a wider range of climate conditions, a hybrid ventilation approach integrating both mechanical and natural ventilation should be carried out. Moreover, further study of ventilation effectiveness, as per Computational Fluid Dynamics (CFD), is also recommended.This research aims to propose and explore natural ventilation schemes for the design of high-performance, non-residential buildings in hot and humid climates. Three such schemes were applied toward retrofitting the existing Hawai‘i Institute of Geophysics buildings on University of Hawai‘i at Mānoa (UHM) campus in Honolulu. The results were investigated by using parametric study and Airflow Network (AN) model, coupled with thermal model in EnergyPlus. Meanwhile, the number of discomfort hours, during the time the buildings are occupied and based on the adaptive thermal comfort, was used as a quantitative index for the performance of the natural ventilation design schemes. The results revealed that pure cross-ventilation is not a feasible mode to deliver adequate thermal comfort to the occupants, per an acceptable number of discomfort hours. However, with the supplementation of vertical ventilation ducts (shafts), the performance of natural ventilation design schemes significantly improved. In these cases, it was found that either ventilation ducts or ventilation windows can be completely closed, thus eliminating the need of one or the other in natural ventilation designs and therefore mitigating the potential for outdoor noise traveling into spaces through ventilation ducts and/or ventilation windows’ openings. This research presents my preliminary investigation toward finding the optimal scheme for natural ventilation design. After the scheme is chosen, the actual geometry of the ventilation ducts and ventilation windows, appropriate louvers and duct fittings, as well as their optimal aspect ratios, should be taken into consideration. For future research to be able to extend to incorporate a wider range of climate conditions, a hybrid ventilation approach integrating both mechanical and natural ventilation should be carried out. Moreover, further study of ventilation effectiveness, as per Computational Fluid Dynamics (CFD), is also recommended.This research aims to propose and explore natural ventilation schemes for the design of high-performance, non-residential buildings in hot and humid climates. Three such schemes were applied toward retrofitting the existing Hawai‘i Institute of Geophysics buildings on University of Hawai‘i at Mānoa (UHM) campus in Honolulu. The results were investigated by using parametric study and Airflow Network (AN) model, coupled with thermal model in EnergyPlus. Meanwhile, the number of discomfort hours, during the time the buildings are occupied and based on the adaptive thermal comfort, was used as a quantitative index for the performance of the natural ventilation design schemes. The results revealed that pure cross-ventilation is not a feasible mode to deliver adequate thermal comfort to the occupants, per an acceptable number of discomfort hours. However, with the supplementation of vertical ventilation ducts (shafts), the performance of natural ventilation design schemes significantly improved. In these cases, it was found that either ventilation ducts or ventilation windows can be completely closed, thus eliminating the need of one or the other in natural ventilation designs and therefore mitigating the potential for outdoor noise traveling into spaces through ventilation ducts and/or ventilation windows’ openings. This research presents my preliminary investigation toward finding the optimal scheme for natural ventilation design. After the scheme is chosen, the actual geometry of the ventilation ducts and ventilation windows, appropriate louvers and duct fittings, as well as their optimal aspect ratios, should be taken into consideration. For future research to be able to extend to incorporate a wider range of climate conditions, a hybrid ventilation approach integrating both mechanical and natural ventilation should be carried out. Moreover, further study of ventilation effectiveness, as per Computational Fluid Dynamics (CFD), is also recommended.This research aims to propose and explore natural ventilation schemes for the design of high-performance, non-residential buildings in hot and humid climates. Three such schemes were applied toward retrofitting the existing Hawai‘i Institute of Geophysics buildings on University of Hawai‘i at Mānoa (UHM) campus in Honolulu. The results were investigated by using parametric study and Airflow Network (AN) model, coupled with thermal model in EnergyPlus. Meanwhile, the number of discomfort hours, during the time the buildings are occupied and based on the adaptive thermal comfort, was used as a quantitative index for the performance of the natural ventilation design schemes. The results revealed that pure cross-ventilation is not a feasible mode to deliver adequate thermal comfort to the occupants, per an acceptable number of discomfort hours. However, with the supplementation of vertical ventilation ducts (shafts), the performance of natural ventilation design schemes significantly improved. In these cases, it was found that either ventilation ducts or ventilation windows can be completely closed, thus eliminating the need of one or the other in natural ventilation designs and therefore mitigating the potential for outdoor noise traveling into spaces through ventilation ducts and/or ventilation windows’ openings. This research presents my preliminary investigation toward finding the optimal scheme for natural ventilation design. After the scheme is chosen, the actual geometry of the ventilation ducts and ventilation windows, appropriate louvers and duct fittings, as well as their optimal aspect ratios, should be taken into consideration. For future research to be able to extend to incorporate a wider range of climate conditions, a hybrid ventilation approach integrating both mechanical and natural ventilation should be carried out. Moreover, further study of ventilation effectiveness, as per Computational Fluid Dynamics (CFD), is also recommended.This research aims to propose and explore natural ventilation schemes for the design of high-performance, non-residential buildings in hot and humid climates. Three such schemes were applied toward retrofitting the existing Hawai‘i Institute of Geophysics buildings on University of Hawai‘i at Mānoa (UHM) campus in Honolulu. The results were investigated by using parametric study and Airflow Network (AN) model, coupled with thermal model in EnergyPlus. Meanwhile, the number of discomfort hours, during the time the buildings are occupied and based on the adaptive thermal comfort, was used as a quantitative index for the performance of the natural ventilation design schemes. The results revealed that pure cross-ventilation is not a feasible mode to deliver adequate thermal comfort to the occupants, per an acceptable number of discomfort hours. However, with the supplementation of vertical ventilation ducts (shafts), the performance of natural ventilation design schemes significantly improved. In these cases, it was found that either ventilation ducts or ventilation windows can be completely closed, thus eliminating the need of one or the other in natural ventilation designs and therefore mitigating the potential for outdoor noise traveling into spaces through ventilation ducts and/or ventilation windows’ openings. This research presents my preliminary investigation toward finding the optimal scheme for natural ventilation design. After the scheme is chosen, the actual geometry of the ventilation ducts and ventilation windows, appropriate louvers and duct fittings, as well as their optimal aspect ratios, should be taken into consideration. For future research to be able to extend to incorporate a wider range of climate conditions, a hybrid ventilation approach integrating both mechanical and natural ventilation should be carried out. Moreover, further study of ventilation effectiveness, as per Computational Fluid Dynamics (CFD), is also recommended.This research aims to propose and explore natural ventilation schemes for the design of high-performance, non-residential buildings in hot and humid climates. Three such schemes were applied toward retrofitting the existing Hawai‘i Institute of Geophysics buildings on University of Hawai‘i at Mānoa (UHM) campus in Honolulu. The results were investigated by using parametric study and Airflow Network (AN) model, coupled with thermal model in EnergyPlus. Meanwhile, the number of discomfort hours, during the time the buildings are occupied and based on the adaptive thermal comfort, was used as a quantitative index for the performance of the natural ventilation design schemes. The results revealed that pure cross-ventilation is not a feasible mode to deliver adequate thermal comfort to the occupants, per an acceptable number of discomfort hours. However, with the supplementation of vertical ventilation ducts (shafts), the performance of natural ventilation design schemes significantly improved. In these cases, it was found that either ventilation ducts or ventilation windows can be completely closed, thus eliminating the need of one or the other in natural ventilation designs and therefore mitigating the potential for outdoor noise traveling into spaces through ventilation ducts and/or ventilation windows’ openings. This research presents my preliminary investigation toward finding the optimal scheme for natural ventilation design. After the scheme is chosen, the actual geometry of the ventilation ducts and ventilation windows, appropriate louvers and duct fittings, as well as their optimal aspect ratios, should be taken into consideration. For future research to be able to extend to incorporate a wider range of climate conditions, a hybrid ventilation approach integrating both mechanical and natural ventilation should be carried out. Moreover, further study of ventilation effectiveness, as per Computational Fluid Dynamics (CFD), is also recommended.This research aims to propose and explore natural ventilation schemes for the design of high-performance, non-residential buildings in hot and humid climates. Three such schemes were applied toward retrofitting the existing Hawai‘i Institute of Geophysics buildings on University of Hawai‘i at Mānoa (UHM) campus in Honolulu. The results were investigated by using parametric study and Airflow Network (AN) model, coupled with thermal model in EnergyPlus. Meanwhile, the number of discomfort hours, during the time the buildings are occupied and based on the adaptive thermal comfort, was used as a quantitative index for the performance of the natural ventilation design schemes. The results revealed that pure cross-ventilation is not a feasible mode to deliver adequate thermal comfort to the occupants, per an acceptable number of discomfort hours. However, with the supplementation of vertical ventilation ducts (shafts), the performance of natural ventilation design schemes significantly improved. In these cases, it was found that either ventilation ducts or ventilation windows can be completely closed, thus eliminating the need of one or the other in natural ventilation designs and therefore mitigating the potential for outdoor noise traveling into spaces through ventilation ducts and/or ventilation windows’ openings. This research presents my preliminary investigation toward finding the optimal scheme for natural ventilation design. After the scheme is chosen, the actual geometry of the ventilation ducts and ventilation windows, appropriate louvers and duct fittings, as well as their optimal aspect ratios, should be taken into consideration. For future research to be able to extend to incorporate a wider range of climate conditions, a hybrid ventilation approach integrating both mechanical and natural ventilation should be carried out. Moreover, further study of ventilation effectiveness, as per Computational Fluid Dynamics (CFD), is also recommended

Gas-Liquid Two-Phase Flow in the Pipe or Channel

The main goal of this Special Issue was to contribute to, highlight and discuss topics related to various aspects of two-phase gas–liquid flows, which can be used both in fundamental sciences and practical applications, and we believe that this main goal was successfully achieved. This Special Issue received studies from Russia, China, Thailand, ROC-Taiwan, Saudi Arabia, and Pakistan. We were very grateful to see that all the papers presented findings characterized as unconventional, innovative, and methodologically new. We hope that the readers of the journal Water can enjoy and learn about the experimental and numerical study of two-phase flows from the published material, and share these results with the scientific community, policymakers and stakeholders. Last but not least, we would like to thank Ms. Aroa Wang, Assistant Editor at MDPI, for her dedication and willingness to publish this Special Issue. She is a major supporter of the Special Issues, and we are indebted to her

Effect of curing conditions and harvesting stage of maturity on Ethiopian onion bulb drying properties

The study was conducted to investigate the impact of curing conditions and harvesting stageson the drying quality of onion bulbs. The onion bulbs (Bombay Red cultivar) were harvested at three harvesting stages (early, optimum, and late maturity) and cured at three different temperatures (30, 40 and 50 oC) and relative humidity (30, 50 and 70%). The results revealed that curing temperature, RH, and maturity stage had significant effects on all measuredattributesexcept total soluble solids