Multi-Objective Optimization in Air-to-Air Communication System Based on Multi-Agent Deep Reinforcement Learning.

With the advantages of real-time data processing and flexible deployment, unmanned aerial vehicle (UAV)-assisted mobile edge computing systems are widely used in both civil and military fields. However, due to limited energy, it is usually difficult for UAVs to stay in the air for long periods and to perform computational tasks. In this paper, we propose a full-duplex air-to-air communication system (A2ACS) model combining mobile edge computing and wireless power transfer technologies, aiming to effectively reduce the computational latency and energy consumption of UAVs, while ensuring that the UAVs do not interrupt the mission or leave the work area due to insufficient energy. In this system, UAVs collect energy from external air-edge energy servers (AEESs) to power onboard batteries and offload computational tasks to AEESs to reduce latency. To optimize the system's performance and balance the four objectives, including the system throughput, the number of low-power alarms of UAVs, the total energy received by UAVs and the energy consumption of AEESs, we develop a multi-objective optimization framework. Considering that AEESs require rapid decision-making in a dynamic environment, an algorithm based on multi-agent deep deterministic policy gradient (MADDPG) is proposed, to optimize the AEESs' service location and to control the power of energy transfer. While training, the agents learn the optimal policy given the optimization weight conditions. Furthermore, we adopt the K-means algorithm to determine the association between AEESs and UAVs to ensure fairness. Simulated experiment results show that the proposed MODDPG (multi-objective DDPG) algorithm has better performance than the baseline algorithms, such as the genetic algorithm and other deep reinforcement learning algorithms.

Study on the thermal release characteristics and the correlation transformation mechanism of microscopic active groups of oxidized coal combustion in a deep mined-out area.

With the normalization of deep mining, the risk of residual coal spontaneous combustion (CSC) in deeply mined areas has gradually increased. To investigate the thermal characteristics and microgroup transformation mechanisms during the secondary oxidation of deep-well oxidized coal, a deep-well oxidation process was simulated in a synchronous thermal analyzer, and the thermal parameters of the oxidized coal were tested. The correlated transformation pathways of microscopic active groups was studied by electron paramagnetic resonance (EPR) and in situ diffuse reflectance (in situ FTIR) experiments during the reoxidation of oxidized coal. The results showed that with increasing deep-well ambient temperature and oxidation temperature, the characteristic temperature of coal gradually decreased, exothermic heat release gradually increased, and active aliphatic structures and -OH, -CHO and other active functional groups gradually accumulated and became distributed more uniformly. When the thermal conditions and oxidation temperature were very high (> 160 °C), the active free radicals in the oxidized coal were rapidly consumed, resulting in a gradual decrease in the characteristic temperature and heat release during the secondary oxidation process, while the contents of peroxy and carboxyl groups continued to increase. In the slow oxidation stage of oxidized coal, methyl groups were mainly transformed with hydroxyl and peroxide groups (r > 0.96), and the associated oxidative consumption of -CHO and -COOH mainly occurred in the rapid oxidation stage (r > 0.99). Geminal diols and peroxy groups are important intermediates in the coal-oxygen composite reaction process. With an increase in the deep-well temperature and initial oxidation temperature, the reoxidation tendency and heat release capacity of residual coal in the goaf gradually increased, and the risk of CSC intensified. The research results provide a theoretical reference for the prevention and control of coal fires in deep mines and play an important role in guiding environmental management and gas emissions reduction measures in mining areas.

Investigation of the thermal behaviour of pre-oxidation coal in deep mines.

As mining continues to increase in depth, the problem of pre-oxidation coal (POC) spontaneous combustion (PCSC) in deep mines is coming to the fore. The effects of thermal ambient temperature and pre-oxidation temperature (POT) on the thermal mass loss (TG) and heat release (DSC) characteristics of POC were studied. The results show that the oxidation reaction process is found to be similar among the coal samples. The majority of mass loss and heat release from the oxidation of the POC is in the stage III and decreases with increasing thermal ambient temperature, while the combustion properties change in the same way, indicating a consequent reduction in the risk of spontaneous combustion. The higher the POT, the more the critical POT tends to be at a lower POT at a higher thermal ambient temperature. It can be demonstrated that higher thermal ambient temperatures and higher POT lower the risk of spontaneous combustion of POC.

Delivery of miR-224-5p by Exosomes from Cancer-Associated Fibroblasts Potentiates Progression of Clear Cell Renal Cell Carcinoma.

OBJECTIVES: Clear cell renal cell carcinoma (ccRCC) is the most common subtype of renal cell carcinoma. Cancer-associated fibroblasts (CAFs) as the primary components of cancer stroma can affect tumor progression by secreting exosomes, while exosomes are carriers for proteins, nucleic acids, and other agents that responsible for delivery of biological information. Given this, exosomes derived from CAFs are emerging as promising biomarkers in clinical cancer diagnosis. Nevertheless, their role in clear cell renal cell carcinoma (ccRCC) remains poorly understood. METHODS: Here, we separated fibroblasts from ccRCC tissue, extracted exosomes, observed their morphology, and detected the expression of exosome marker proteins including Hsp70, CD9, and CD63. In the meantime, we labeled exosomes and performed coculture experiment to verify the delivery of miR-224-5p from CAFs to 769-P cells with exosomes as a carrier, so as to clarify the effect of CAF-derived exosomes on ccRCC cell malignant behaviors, as well as to discuss how miR-224-5p involves in above regulation. RESULTS: Transmission electron microscopy was firstly applied, and it was noted that the exosomes we isolated were in normal range. Besides, Western blot also confirmed the presence of exosome marker proteins Hsp70, CD9, and CD63. Furthermore, coculture experiments were performed and the CAF-derived exosomes were observed to be able to facilitate the malignant behaviors of ccRCC cells, and the exosomal miR-224-5p could be internalized by ccRCC cells to participate in regulation of cell proliferation, migration, invasion, and apoptosis. CONCLUSION: To sum up, miR-224-5p can enter ccRCC cells via CAF-derived exosomes, in turn, promoting the malignant behaviors of ccRCC cells, which indicates that miR-224-5p has the potential severing as a therapeutic target for ccRCC.