Principle of 6G Wireless Networks: Vision, Challenges and Applications

The 5G mobile communication has now become commercially available. Furthermore, research across the globe has begun to improve the system beyond 5G and it is anticipated that 6G will deliver higher quality services and energy efficiency than 5G. The mobile network architecture needs to be redesigned to meet the requirements of the future. In the wake of the commercial rollout of the 5G model, both users and developers have realized the limitations of the system when compared to the system's original premise of being able to support the vast applications of connected devices. The article discusses the related technologies that can contribute to a robust and seamless network service. An upheaval in the use of vast mobile applications, especially those powered and managed by AI, has opened the doors to discussion on how mobile communication will evolve in the future. 6G is expected to go beyond being merely a mobile internet service provider to support the omnipresent AI services that will form the rock bed of end-to-end connected network-based devices. Moreover, the technologies that support 6G services and comprehensive research that enables this level of technical prowess have also been identified here. This paper presents a collective wide-angle vision that will facilitate a better understanding of the features of the 6G system.

Neural Identification of a Temperature Field in the Storing Phase of Thermal Energy in Rock Bed Thermal Storage

Thermal energy stored within a rock bed thermal storage system, which is mostly used in agriculture, can be identified during the storage phase using mathematical models based on heat transfer, which concerns batteries running in a vertical setting. However, this requires the conversion of differential equations into algebraic equations, as well as knowledge about the initial and boundary conditions. Furthermore, a lack of information or incomplete information about the initial conditions makes it difficult or impossible to evaluate the volume of stored energy, or can cause significant errors during evaluation. Such situations occur in systems equipped with a rock battery, in which solar collectors act as source of energy. Considering the above, as well as the lack of a model for batteries in a vertical setting, we identified the need for research into the storage phase of rock bed thermal storage systems, working in a horizontal setting, and generating MLP-type neural models. Among these models, MLP 4-7-1 turned out to be the best both in terms of the values of regression statistics and possibilities of generalization. According to the authors, artificial neural models depicting temperature changeability in storage phase will be helpful in the development of a new methodology that can predict the heat volume in rock bed thermal storage systems.

Numerical Simulation of Rock-bed Solar Thermal Storage Energy

Solar dryers are increasingly being applied to dry fruits and vegetables in order to increase their shelf-lives. In the sunny-belt countries, the availability of solar irradiance is taken for granted and the mean daily solar irradiation is often used as the design basis for a solar dryer. The predicted performance of the solar irradiance is therefore inherently inaccurate. Contemporary solar dryer designs incorporate thermal energy storage (TES) systems for application after sunset. The performance of such TES systems is often determined experimentally. In this study, mathematical models have been developed and by numerical simulation using the technique of Finite Differential Method (FDM) and MATLAB programming, the performances of solar irradiance as well as that of the TES system have been predicted. The simulation results were secured to inform the design of the solar dryer for fruits and vegetables in the sun-belt countries.

Simulation of Mosul Dam Break Using Finite Volume Method

Mosul dam is an earth-fill embankment located north of Iraq on the Tigris River forming a reservoir with 11.11 km3 water storage capacity which is the largest dam in the country. The dam is built on a rock bed foundation, in which the dissolution process is dynamic in the zone where gypsum and anhydrite layers present. During the construction development seepage locations were found in the dam foundation and the grouting process is in progress until now to control this problem. Therefore, the possibility of the Mosul dam break is highlighted by previous studies. In this research, a FORTRAN code based on the finite volume method is modified to solve the two-dimensional shallow water equations and simulating the Mosul dam break. The computational domain discretized using unstructured triangular mesh. The solver applied Harten lax van leer with contact (HLLC) wave approximate Riemann solver to calculate the cell interface fluxes, and the semi-implicit scheme employed to solve the friction source term. The numerical scheme applied to two benchmark test cases, and the results showed that the presented model was robust and accurate especially in handling wet/dry beds, mixed flow regimes, discontinuities, negative water depths, and complex topography. The results of this study demonstrate that flood waves may reach the center of Mosul city in < 6 h and water depth may rise to 34 m after 7 h of Mosul dam breaking. Finally, the simulation results of the Mosul dam break were used to prepare an emergency action plan.

Effects of the Rock-Bed Heat Storage System on the Solar Greenhouse Microclimate

The Mediterranean area is characterized by intense radiation generating high temperatures during the day in the greenhouse and low temperatures during the night. The temperature gap problem between the daytime and the nocturnal period which characterizes the region requires the use of greenhouses with a thermal storage system. A greenhouse equipped with a sensible heat storage system using a rock-bed, was compared to a witness one, under the same climatic conditions. Measurements were performed on the microclimate parameters of both greenhouses, such as temperature and relative humidity. Our work is based on an experimental analysis of greenhouse microclimate and evaluating the evolution of temperature and relative humidity prevailing inside the greenhouse. It has been found that the system efficiency is improved due to the storing of heat in excess during the daytime. This stored energy is used during night. The main obtained results showed that the heat storage system allowed an increase in the air temperature up to 0.9℃ and a decrease of the relative humidity about 3.4% during the night compared to the witness greenhouse. The improvement in the heated greenhouse microclimate during night has a very positive impact on the quality of fruit and yield.

The Influence of the Shape of Granite on the Heat Storage Process in a Rock Bed

Granite is one of those materials that due to its thermal parameters is used as a filling for storage beds, including high-temperature ones. The article analyzes local material that was extracted in Strzegom, Poland. The purpose of the paper is the assessment of storage material with regard to its cooperation with a heat source that is available for a short time, e.g., a solar installation. Three different shapes of granite material were tested: rock, cube and sphere. Each shape has its advantages and disadvantages, which are associated with economic and strength aspects. The article presents experimental tests of the material, which were conducted in order to determine the efficiency of the charging process. The results show that rock-shaped granite filling elements are characterized with the best parameters during the charging process, and that they obtained the highest first- and second-law efficiency in the entire tested range of inlet air temperature and flow rate. The efficiency of the cube-shaped granite was lower than the sphere-shaped granite. This means that the efficiency does not directly depend on the coefficient of sphericity of the elements that fill the storage bed. The determination of the second law efficiency showed that the highest use of energy supplied with hot air occurs after 1 h of charging the accumulator in the case of all the analyzed geometries. At the end of the paper, the influence of the obtained results on the process of modelling the charging of a storage bed filled with elements of non-spherical geometry is also discussed.