As an aerial base station (BS), unmanned aerial vehicle (UAV) has been considered as a promising platform to provide wireless data service in future networks due to its flexible, swift and low cost features. However, ...
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As an aerial base station (BS), unmanned aerial vehicle (UAV) has been considered as a promising platform to provide wireless data service in future networks due to its flexible, swift and low cost features. However, since the suddenness and randomness of ground users’ (GUs’) data requirements, it is challenging for the UAV BSs to dynamically make decisions to provide real-time data services to GUs. In a multi-mode UAV-assisted wireless network, we formulate a multi-objective optimization problem to minimize the average peak age of information (APAoI) and energy consumption of UAVs, and to maximize the accumulated service data (ASD) for GUs. Therefore, this paper proposes the multi-agent hybrid twin delayed deep deterministic policy gradient (MAHTDDDPG) algorithm with hybrid action space design, which is empowered by centralized training and distributed execution (CTDE) framework. In the proposed algorithm, the UAVs can cooperatively make decisions by sharing the GU status information, in a result of jointly optimizing the UAV trajectory, mode selection and transmit power. Simulation results demonstrate that our proposed approach achieves 79.6% and 120.4% higher reward than MADDPG algorithm and HTD-DDPG algorithm respectively. IEEE
Solid rocket motors have important applications in the propulsion of trans-media vehicles and underwater launched *** this paper,the ignition start-up process of an underwater solid rocket motor across a wide depth ra...
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Solid rocket motors have important applications in the propulsion of trans-media vehicles and underwater launched *** this paper,the ignition start-up process of an underwater solid rocket motor across a wide depth range has been numerically studied.A novel multi-domain integrated model has been developed by combining the solid propellant ignition and combustion model with the volume of fluid multiphase *** integrated model enables the coupled simulation of the propellant combustion and gas flow inside the motor,along with the gas jet evolution in the external water *** detailed flow field developments in the combustion chamber,nozzle,and wake field are carefully *** variation rules of the internal ballistics and thrust performance are also *** effects of environmental medium and operating depth on the ignition start-up process are systematically *** results show that the influence of the operating environment on the internal ballistic characteristics is primarily reflected in the initial period after the nozzle closure *** development of the gas jet in water lags significantly compared with that in *** the water depth increases,the ignition delay time of the motor is shortened,and the morphology evolution of the gas jet is significantly compressed and ***,the necking and bulging of the jet boundary near the nozzle outlet and the consequent shock oscillations are intensified,resulting in stronger fluctuations in the wake pressure field and motor thrust.
In this study, we proposed an Android based smartphone application to support the formation of exercise habits for people who cannot secure sufficient time for exercise. In this application, users input their schedule...
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Higher-order modes of the neutron diffusion/transport equation can be used to study the temporal behavior of nuclear reactors and can be applied in modal analysis, transient analysis, and online monitoring of the reac...
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Higher-order modes of the neutron diffusion/transport equation can be used to study the temporal behavior of nuclear reactors and can be applied in modal analysis, transient analysis, and online monitoring of the reactor core. Both the deterministic method and the Monte Carlo(MC) method can be used to solve the higher-order modes. However, MC method, compared to the deterministic method, faces challenges in terms of computational efficiency and α mode calculation stability, whereas the deterministic method encounters issues arising from homogenization-related geometric and energy spectra *** on the higher-order mode diffusion calculation code HARMONY, we developed a new higher-order mode calculation code, HARMONY2.0, which retains the functionality of computing λ and α higher-order modes from HARMONY1.0, but enhances the ability to treat complex geometries and arbitrary energy spectra using the MC-deterministic hybrid two-step strategy. In HARMONY2.0, the mesh homogenized multigroup constants were obtained using OpenMC in the first step,and higher-order modes were then calculated with the mesh homogenized core diffusion model using the implicitly restarted Arnoldi method(IRAM), which was also adopted in the HARMONY1.0 code. In addition, to improve the calculation efficiency, particularly in large higher-order modes, event-driven parallelization/domain decomposition methods are embedded in the HARMONY2.0 code to accelerate the inner iteration of λ∕α mode using OpenMP. Furthermore, the higher-order modes of complex geometric models, such as Hoogenboom and ATR reactors for λ mode and the MUSE-4 experiment facility for the prompt α mode, were computed using diffusion theory.
In this tutorial paper, we explore the field of quantized feedback control, which has gained significant attention due to the growing prevalence of networked control systems. These systems require the transmission of ...
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In this tutorial paper, we explore the field of quantized feedback control, which has gained significant attention due to the growing prevalence of networked control systems. These systems require the transmission of feedback information, such as measurements and control signals, over digital networks, presenting novel challenges in estimation and control design. Our examination encompasses various topics, including the minimal information needed for effective feedback control, the design of quantizers, strategies for quantized control design and estimation,achieving consensus control with quantized data, and the pursuit of high-precision tracking using quantized measurements.
This paper mainly addresses control problems of strict-feedback systems(SFSs)with increasing *** with the commonly-considered SFSs where the subsystems have the same dimension,we aim to handle more complex cases,i.e.,...
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This paper mainly addresses control problems of strict-feedback systems(SFSs)with increasing *** with the commonly-considered SFSs where the subsystems have the same dimension,we aim to handle more complex cases,i.e.,the subsystems in the considered SFSs are assumed to have increasing *** transforming the systems into highorder fully-actuated system(HOFAS)models,the stabilizing controllers can be directly *** first-order SFSs,secondorder and high-order SFSs are also considered.
We proposed and compared three methods(filter burnup,single energy burnup,and burnup extremum analysis)to build a high-resolution neutronics model for 238Pu production in high-flux *** filter burnup and single energy ...
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We proposed and compared three methods(filter burnup,single energy burnup,and burnup extremum analysis)to build a high-resolution neutronics model for 238Pu production in high-flux *** filter burnup and single energy burnup methods have no theoretical approximation and can achieve a spectrum resolution of up to~1 eV,thereby constructing the importance curve and yield curve of the full energy *** burnup extreme analysis method combines the importance and yield curves to consider the influence of irradiation time on production efficiency,thereby constructing extreme *** three curves,which quantify the transmutation rate of the nuclei in each energy region,are of physical significance because they have similar distributions.A high-resolution neutronics model for ^(238)Pu production was established based on these three curves,and its universality and feasibility were *** neutronics model can guide the neutron spectrum optimization and improve the yield of ^(238)Pu by up to 18.81%.The neutronics model revealed the law of nuclei transmutation in all energy regions with high spectrum resolution,thus providing theoretical support for high-flux reactor design and irradiation production of ^(238)Pu.
To develop a method for estimating age-related decline using the analysis of daily conversation characteristics of elderly individuals, we compared the conversation traits of elderly people living in serviced housing ...
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This study presents a support system for rehabilitating patients with mental illnesses using data from wearable devices. Utilizing the Fitbit Sense 2 smartwatch, the system collects daily life data and displays it gra...
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designing indoor scenes to align with user preferences is expected to be utilized in virtual environments including the metaverse. A previous approach is to automatically adjust the color of an object's texture pl...
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