Maximum Operation Time Research Articles

Efficient Operation Algorithm of UAVs for Tourist Safety: Case of the Hallasan Mountain Trail in Jeju Island

Tourist safety is one of the most important factors for tourists when choosing a tourism destination. Jeju Island’s Hallasan Mountain Trail is a trail that connects the mid-slope of Hallasan, the main mountain on Jeju volcanic island, and boasts very beautiful scenery. However, tourist safety has become an issue as accidents continue to occur every year. In this study, an efficient operation algorithm that can minimize the total cost with a mixed-integer linear programming (MILP) model is developed, considering the introduction of a UAV patrol system on the Hallasan Mountain Trail, which is difficult to access by vehicles. The application of different speeds for patrol and nonpatrol routes, the selection of candidate sites for UAV stations with easy vehicle access, and the sensitivity analysis of patrol speed and maximum operation time considering the performance improvement of UAVs are the contributions of this study. The results show that stations are installed as close as possible to the trail courses and that lower-performance UAVs are utilized that can patrol the trail courses at a given time. The sensitivity analysis also confirmed that the total cost can be minimized by reducing the number of stations and UAVs or replacing higher-performance UAVs with lower-performance UAVs.

Fouling and energy consumption impede electrochemical disinfection of constructed wetland effluents

Electrochemical disinfection (ECD) of constructed wetlands (CWs) effluents via in situ chlorine electrogeneration has been proposed for decentralised water treatment and reclamation. Studies demonstrating the feasibility of continuous ECD of CW effluents in field conditions for several weeks are scarce. Here, a pilot-scale CW was operated for 28 weeks to treat a calcium-rich wastewater stream (131 ± 42 mg L−1) for reclamation. Five electrochemical cell configurations were designed to continuously disinfect the effluent from the pilot-scale CW, differing in the water route, membrane type and catholyte. All configurations inactivated pathogens to levels considered safe for water reclamation. For four configurations, the maximum operating times without maintenance were short (< 1 week) due to calcium-based precipitates inducing membrane and cathode scaling. An additional configuration used rainwater as a cathodic influent for producing an alkaline stream to precipitate mostly calcium carbonate upstream from the ECD system. This avoided premature reactor failure, allowing 21 weeks of operation without apparent scaling. However, the alkaline stream demanded higher charge densities to be neutralised at the anode via water oxidation before a sufficient chlorine evolution. Thus, the flow rate of water treated (1.8 L h−1) was 4.6 times lower than for the other configurations. The resulting energy consumption (5.9 kWh m−3) was considered high for water reclamation. This work illustrates the practical aspects impeding stability and efficiency for ECD of hard waters and highlights possible strategies to deal with adverse scaling.

Stability analysis of a multilayer diffusion-reaction heat transfer problem with a very large number of layers

The stability of thermal conduction problems is of much practical interest in the context of Li-ion batteries, power electronic devices, chemical reactors and other engineering systems. While past work in predicting the thermal stability of a multilayer diffusion-reaction problem has been carried out using pole analysis or by determining imaginary eigenvalues of the problem, such techniques are impractical when the number of layers in the problem is very large. This work presents an exact analysis of the stability of a multilayer diffusion-reaction problem, in which the number of layers may be very large. Using homogenization and Heaviside functions based representation of thermophysical properties and parameters, it is shown that the stability of such a system may be easily predicted by computing the determinant of a matrix containing contributions from each layer/interface. Results from the present work are shown to correctly reduce to results from past work for pure-diffusion and single-layer special cases, as well as agree well with numerical simulations. Threshold for thermal stability of a representative Li-ion battery pack containing 1000 Li-ion cells is determined. It is shown that stability of the system is governed by a balance between temperature-dependent heat generation, diffusion and heat removal from the boundary. A key result of practical interest is that even small improvement in thermal diffusivity of Li-ion cells may greatly help reduce the risk of thermal instability. Additionally, practical guidelines for the maximum permissible operating time of a battery pack to avoid thermal runaway are discussed. This work advances the theoretical understanding of multilayer diffusion-reaction problems, and helps understand the thermal stability of Li-ion battery packs containing a very large number of cells, which is very difficult to analyze using traditional techniques.

Gradient projection-based trajectory tracking control for automatic guided vehicle

In order to solve the problems of long operation time for solving the trajectory tracking controller and low real-time tracking. This paper proposes an improved model predictive control algorithm. By introducing the gradient projection method (GPM), the projection direction is used as the fastest descent direction of the objective function, which is used to reduce the number of iterations of the operation. Meanwhile, this paper adds constraints and relaxation factors to improve the trajectory tracking accuracy and prevent the controller operations from falling into local optimal solutions. Simulation by Simulink, the improved model predictive control algorithm reduces the average operation time by 24.74% and the single maximum operation time by 36.04%, effectively improving the real-time trajectory tracking performance. Finally, the verification experiment of trajectory tracking control is carried out by actual vehicle, proving the method’s effectiveness.

Collaborative orchard pesticide spraying routing problem with multi-vehicles supported multi-UAVs

The application of UAVs in orchard management presents a substantial opportunity to enhance efficiency and promote environmentally friendly agricultural production. While individual UAVs encounter limitations, such as endurance constraints, these challenges can be mitigated through collaborative efforts involving multiple vehicles and UAVs. This study addresses the issue of multi-UAV cooperative orchard path planning with multiple vehicles by formulating a mathematical optimization model aimed at minimizing the maximum UAV operation time. In the proposed model, the vehicle solely provides batteries and supplies to the UAV. To efficiently solve this model, we propose an improved Simulated Annealing-Lin Kernighan Helsgaun (SA-LKH) algorithm. The proposed algorithm utilizes the K-means and convex hull algorithm to generate the initial solution. Subsequently, the paths of each group of UAVs and vehicles are optimized based on the LKH algorithm. Additionally, we construct a directed perturbation operator that perturbs the maximum and minimum time-consuming paths to achieve fast convergence of the algorithm. The results from four different cases demonstrate that, compared to the general variable neighborhood search algorithm, the improved Ant Colony Algorithm and Improved Genetic Algorithm, the proposed algorithm has demonstrated an average improvement in solution quality of 3.41%, 5.72% and 9.67%, respectively. The proposed method effectively enhances the solution quality, which can provide valuable insights into green cleaning management of orchards.

Maximum Operating Time of Steel 25X1M1FA Metal Rotors During Prolonged Operation of 60 MW Turbines

Maximum Operating Time of Steel 25X1M1FA Metal Rotors During Prolonged Operation of 60 MW Turbines

Robust predictive minmax fault‐tolerant control for multi‐phase batch processes under partial actuator faults and asynchronous switching

AbstractIn view of the uncertainties, partial actuator faults, asynchronous switching as well as unknown external interference in multi‐phase batch processes, a robust predictive minmax fault‐tolerant control approach is presented. First, considering that a controller and a system state cannot switch synchronously during switching, a match‐and‐mismatch switching model is constructed. Then, an output tracking error is introduced to establish an equivalent extended switching model. In this extended model, the robust control issue is transformed into the minmax optimization issue by establishing the minmax performance index. On this basis, the control laws with control input and interference input are designed. Second, sufficient conditions are given to assure the system separately has asymptotic and exponential stabilities in each phase and batch. By calculating the given sufficient conditions online, the gains of the control laws, and the minimum and maximum operating time under match and mismatch cases are obtained. With the maximum operating time, the controller receives the switching signal beforehand to eliminate the mismatch case of switching. Additionally, a robust criterion is supplied to confirm the system's robustness. Finally, a simulation study of an injection molding process shows that the approach is valid and feasible.

Numerical investigation and optimisation of solid–solid phase change material composite-based plate-fin heat sink for thermal management of electronic package

Phase Change Material based Thermal Management Systems show promise in electronic packaging systems for safe operation, acting as a thermal storage element to prevent sudden temperature surges, enhancing operational time and mitigating electronic system failures. Therefore, the meticulous design of a solid–solid phase change material (SSPCM) based heat sink with fins is imperative for effective electronic thermal management by improving its safe operational time. This study performs a numerical analysis of two-dimensional transient heat transfer for the SSPCM-based plate-fin heat sink using the modified enthalpy porosity method, where the plate fins serve as Thermal Conductivity Enhancers (TCEs). Neopentyl glycol with 6% (w/w) Copper oxide nanoparticle is used as the SSPCM composite. Enhancement ratio based on safe operational time at different power levels (2–6 W) with different percentages of TCE and fin count recorded variation from 1.32 to 13.7. The TCE integration is more effective at higher power levels. The optimisation of SSPCM-based heat sink design for maximum safe operational time is accomplished through Response Surface Methodology. The significance of the TCE fraction, number of fins, heat generation rate, and interaction effects over the safe operational time are observed. The correlation for safe operational time as a function of TCE volume fraction, fin count and heat generation rate is developed. TCE volume fraction possesses the highest influencing factor over safe operational time at lower and higher power levels compared to fin count. At 2 W and 6 W, a maximum change in safe operational time is observed from 72.7% at 2 W to 83.45% at 6 W. The heat sink with 0.262 volume fraction of TCE and 11 fins is the optimised design that can provide the desirable safe operational time for the tested range of power levels.

Coordination of Directional Overcurrent Relays using Growth Optimizer

The protection system plays a crucial role in the generation, transmission, and distribution systems of a power network. Among various protection relay types, Directional Overcurrent Relays (DOCRs) are the most used. When abnormal conditions are detected, these relays trigger the tripping of protection devices by detecting the direction and magnitude of current flow and isolating faulty parts of the system. The present article proposes a novel approach for the coordination and settings of DOCRs using the Growth Optimizer (GO) algorithm; the main objective is to minimize the sum of operation time of the relays while ensuring the minimal time gap between primary and backup relays. This optimization problem is subject to different constraints including maximum allowable operating times, relay coordination margins, and discrete values for pickup current settings. The technique is applied to the IEEE 4-bus, 8-bus, and 15-bus test systems, and its performance is compared with that of other optimization algorithms. Results show that the proposed approach provides the proper coordination of protection systems with a high, robust, and computationally acceptable speed of convergence.

An improved gray wolf optimization to solve the multi-objective tugboat scheduling problem.

With the continuous prosperity of maritime transportation on a global scale and the resulting escalation in port trade volume, tugboats assume a pivotal role as essential auxiliary tools influencing the ingress and egress of vessels into and out of ports. As a result, the optimization of port tug scheduling becomes of paramount importance, as it contributes to the heightened efficiency of ship movements, cost savings in port operations, and the promotion of sustainable development within the realm of maritime transportation. However, a majority of current tugboat scheduling models tend to focus solely on the maximum operational time. Alternatively, the formulated objective functions often deviate from real-world scenarios. Furthermore, prevailing scheduling methods exhibit shortcomings, including inadequate solution accuracy and incompatibility with integer programming. Consequently, this paper introduces a novel multi-objective tugboat scheduling model to align more effectively with practical considerations. We propose a novel optimization algorithm, the Improved Grey Wolf Optimization (IGWO), for solving the tugboat scheduling model. The algorithm enhances convergence performance by optimizing convergence parameters and individual updates, making it particularly suited for solving integer programming problems. The experimental session designs several scale instances according to the reality of the port, carries out simulation experiments comparing several groups of intelligent algorithms, verifies the effectiveness of IGWO, and verifies it in the comprehensive port area of Huanghua Port to get the optimal scheduling scheme of this port area, and finally gives management suggestions to reduce the cost of tugboat operation through sensitivity analysis.

Ultrafast spin dynamics in magnetic trimer and tetramer clusters: a step towards prototypic spin-SHIFT registers

Ultrafast magnetic dynamics is a necessary ingredient for magnetic recording and ultrafast information processing. The shift functionality, although not mandatory for Boolean logic, is always implemented in CMOS CPUs and therefore must be also present in magnetic logic. In this respect, using ab initio calculations we show ultrafast spin dynamics in molecular clusters such as Co3 +CO and Ni4. In this work, we establish that clusters with magnetic atoms can provide a theoretical toolbox for efficient spin charge dynamics whose operation time can range up to a few picoseconds. The prime underlying mechanism for all spin manipulation scenarios in the above mentioned clusters are laser-induced Λ processes where the laser parameters are fully optimized using a genetic algorithm. In general, a structural asymmetry enforces substantial spin localization on the active centers of both magnetic clusters. Keeping in mind the shift functionality, we theoretically suggest a series of spin-transfer scenarios between the Co and Ni atoms in each of these two clusters independently to construct a 3-bit and a 4-bit cyclic spin-SHIFT register, respectively. The maximum operational time for both logic devices is 2 ps, which is much faster than the response time of conventional spintronic devices. Additionally, for a better understanding of the transfer cycles, their feasibility and reversibility are also investigated through the analysis of the optical spectra of the related states. Our results provide important theoretical guidance for ultrafast spin manipulation in molecular structures as well as their potential spin functionality, and thus step closer to the realization of future spin-based logic devices and quantum computation. This effectively motivates the investigation and precise establishment of the shift functionality in magnetic trimers and tetramers.

Parameters collaborative optimization design and innovation verification approach for fuel cell distributed drive electric tractor

Fuel cell distributed drive electric tractors (FCDET) are one of the necessary means to achieve truly green agriculture. However, low traction efficiency, poor control coordination, and excessive energy consumption are the main reasons hindering the industrialization of FCDET. This paper proposed a parametric collaborative optimization design method and innovative verification system that considers the drive system and energy system. Based on the tractor plowing operating conditions, a 7-DOF coupled dynamics model of the distributed drive system and a tire-soil interaction model were established, and the key component selection and parameter matching were completed. On the drive system optimization level, the front and rear wheelside transmission ratios are optimized based on a multi-island genetic algorithm (MIGA). On the energy system optimization level, the globally optimal power distribution ratio is found based on the dynamic programming algorithm (DP). A complete experimental prototype verification system is constructed based on the MATLAB/Simulink-NI PXI joint simulation platform, physical prototype test bench, and real vehicle multi-index test platform. The results show that the average efficiencies of the optimized drive and energy system are increased by 0.38 % and 3.82 %, the total energy consumption (total hydrogen consumption) is reduced by 25.40 % and 15.39 %, respectively. The maximum fault-free operating time is 5.5h, the average traction power is 21.07 kW, and the average traction force is 10610 N in the all-wheel drive mode. The experimental results fully demonstrate that the electric tractor with the fuel cell distributed drive system as the core can meet the verification of multiple indicators. This study can provide a new theoretical basis and technical verification method for the optimal design and system control of fuel cell distributed drive electric tractors.

The quantum Carnot-like heat engine: The level degenerate case

The two-level quantum heat engines have been studied extensively. Before that, the optimization of most heat engines was mainly concentrated in non-degenerate cases. We consider the level degeneracy, then calculate the maximum operation time and the irreversible dissipation coefficient of the two-level system under the scheme of linear tuned levels. In the high-temperature limit, we find that the level degeneracy affects the maximum power of the two-level heat engine. Especially in the case of the same degeneracy of the ground state and the excited state, the influence is the greatest. In addition, we also show that the degeneracy does not affect the efficiency at maximum power and the consistent relation of the two-level Carnot-like heat engine.

МОДЕЛЬ ПРОГНОЗИРОВАНИЯ РЕСУРСА УПРОЧНЕННЫХ МОЛОТКОВ КОРМОДРОБИЛЬНЫХ МАШИН

During operation, the working parts (hammers) of hammertype feed-crushing machines are subjected to intense wear. The maximum wear of the working edge of the hammer is considered to be wear up to the main axis of symmetry. To reduce wear and increase the service life of the hammer, a technology of combined hardening of the working edge of the hammer with a hard alloy plate using iron-carbon solder is proposed. This work is based on theoretical substantiations and experimental processing of production tests of hardened hammers. (Research purpose) The research purpose is searching for the regularities of the wear process of hardened hammers from operating time during the operation of the feed crushing machine. (Materials and methods) The design and technological parameters and mechanical properties of the materials of the hardened hammer were substantiated. Methods of processing the results of production tests based on mathematical statistics and reliability theory, comparative methods of analysis of hardened and serial hammers were presented. (Results and discussion) The results of studies of experimental hardened hammers were presented, in which the mechanical strength and the magnitude of the diffusion zone of the soldered connection of a hard alloy with the material of the hammer and the iron-carbon solder used in this case were determined. We carried out a theoretical analysis of the dependence of hammer wear on operating time and constructed a mathematical model for predicting the life of a hardened hammer. It was determined as a result of theoretical studies that with the combined hardening of the working edge of the hammer of the feed-crushing machine with a hard alloy VK8 using iron-carbon solder, the maximum operating time increases by 2.76 times. (Conclusions) The results of theoretical studies and production tests prove that the resource of hardened hammers has increased 3.5 times compared to serial ones. The constructed mathematical model for predicting the life of hardened hammers accurately reflects the results of experimental values of the dependence of hammer wear on operating time.

Optimal time separation modeling and simulation for stable neon isotopes in a transient square cascade: a comprehensive study

This study simulates the separation of stable Neon isotopes in a transient square cascade using the Crank–Nicolson method and the q-iteration method. The simulations show that each isotope has an optimal value in either the product or waste streams at a specific time, which affects the cost of separation. The results demonstrate that the optimal separation time for Ne-20 increases with the feed concentration and is influenced by the unit separation factor. Depending on the feed concentration and separation parameter, Ne-21 may be enriched in either the product or waste stream. The optimal separation time for Ne-22 is the maximum operation time and is not affected by changes in feed concentration or unit separation factor. Calculating the optimal separation time is crucial for obtaining target isotopes with specific purity at a designated time, depending on their intended applications.

Electro-Thermal Analysis of a Pouch–Type Lithium–Ion Battery with a High Discharge Rate for Urban Air Mobility

The dynamic behavior and thermal performance of a high-power, high-energy-density lithium-ion battery for urban air mobility (UAM) applications were analyzed by using an electro-thermal model. To simulate the behavior of pouch-type nickel-cobalt-manganese (NCM) lithium–ion batteries, a battery equivalent circuit with a second order of resistance–capacitance (RC) elements was employed. The values of the RC models were determined by using curve fitting based on experimental data for the lithium-ion battery. A three–dimensional model of the lithium-ion battery was created, and a thermal analysis was performed while considering the external temperature and flight time under a 20 min load condition. At an external temperature of 20 °C, the heat generation increased proportionally to the square of the current as the C–rate increased. For 3C, the reaction heat source was 45.5 W, and the average internal temperature of the cell was 36 °C. Even at the same 3C, as the external temperature decreased to 0 °C, the increase in internal resistance led to a greater reaction heat source of 58.27 W, which was 36.9% higher than that at 20 °C. At 5C, the maximum operating time was 685.6 s. At this point, the average internal temperature of the cell was 59.8 °C, which allowed for normal operation. When the C–rate of the battery cell reached 8, which was the momentary maximum high-discharge condition, the temperature sharply rose before the state of charge (SoC) reached 0. With an average internal cell temperature of 80 °C, the maximum operating time became 111.9 s. This met the design requirements for urban air mobility (UAM) in this study.

Experimental Investigation of a Uniaxial Dielectric Elastomer Generator

Abstract The widespread use of battery-powered electronic devices creates the need to develop methods to extend their maximum operating time. This can be achieved by using ambient energy, which would otherwise be dissipated. The conversion of energy, usually mechanical energy, into electric energy takes place in energy harvesters. Energy harvester systems based on a dielectric elastomer (DE) are a relatively new field that is being constantly developed. Due to their features, dielectric elastomer generators (DEGs) may complement the currently dominant piezoelectric harvesters. The major feature of employing a hyperelastic material is that it allows relatively large displacements to be utilised for generating energy, which is impossible in the case of piezoceramics. This article presents a DEG designed to operate under uniaxial tensile loads and which has a multilayer structure, describes the general operating principles of a DEG, explains the construction and assembly process of the investigated design and shows the electric circuit necessary to properly direct current flow during the DEG operation. The experimental part consists of two series of tests based on a central composite design (CCD). The objective of the first part was to map a capacitance response surface of the DEG in the selected range of the cyclic mechanical load. The second part concerned the amount of generated energy for the specific load case as a function of operating voltages. The result of the work is the formulation of regression models that allow the characteristics of the presented DEG design to be identified.

Analytical solution, optimization and design of a phase change cooling pack for cylindrical lithium-ion batteries

Due to the world’s transition to clean energy, the utilization of energy and power storage systems such as lithium-ion batteries has been widely welcomed. The most crucial problem of using these batteries is the large amount of heat production during their operation, which can affect their correct function. Many methods have been investigated to manage and control the temperature of these batteries. One of these methods is to employ phase change materials (PCMs). Despite numerous experimental and numerical studies about cylindrical lithium-ion batteries, there is still a gap in an analytical solution for PCM-based thermal management of them. In the present study, the cooling process of 18650 cylindrical lithium-ion batteries through PCM has been analytically investigated in cylindrical coordinates. For this purpose, the exact solution of the phase transition in cylindrical coordinates is generalized and coupled with the thermal resistance method for the cooling process of this type of battery. In this solution, the temperature distribution in both solid and liquid phases has been considered. Also, the effect of two different types of PCM, namely calcium chloride hexahydrate (PCM1) and paraffin wax (PCM2), and parameters such as ambient temperature, rate of charge/discharge, and thermophysical properties of the PCM on the battery cooling process have been investigated. Moreover, the effect of considering cell internal temperature field and natural convection of the liquid PCM has been evaluated. The results show that for PCM1 in discharge rates of 2C, 4C, and 6C the corresponding required PCM thicknesses are 1.5, 3.1, and 3.8 mm, respectively. In addition, their temperature rises are 2.4, 3.7, and 4.6 °C, in their maximum operation times, respectively. Also, since the thermal conductivity of PCM1 (ks=1.008, kl=0.561W/(m.K)) is higher than that of the PCM2 (ks=0.21, kl=0.18W/(m.K)), the temperature rise in the cell is about 6 °C lower when the former is applied for a single cell. Eventually, the obtained results are generalized for the design of the optimal battery pack which contains 18650 cells surrounded with PCM.

Thermal analysis and optimization of metal foam PCM-based heat sink for thermal management of electronic devices

Efficient thermal management in electric devices is highly essential for ensuring the reliability and durability of electronics. This study aims to investigate the thermal performance and optimization of metal foam PCM-based heat sink for thermal management units. Different design parameters, such as PCM types (RT31, RT42, and RT55), metal foam porosities (85%, 90%, and 95%), and metal foam materials, are studied to determine heat sink optimal parameters, considering various critical temperatures: 40 °C, 50 °C, 60 °C and 70 °C. The volume-averaged method is used to simulate the heat transfer, phase change, and fluid flow within the heat sink unit. Heat transfer between PCM and metal foam is established using a thermal non-equilibrium model. The results show that the usage of metal foam is conducive to the thermal performance enhancement of heat sinks. Among the three parameters, PCM types show a considerable effect on thermal performance of heat sinks, e.g., the maximum operation time of heat sinks with RT31 is about 5 times that of heat sinks with RT55 for the critical temperature of 40 °C. Among all the cases, heat sinks using RT31 and aluminum foam perform optimally, which can achieve the optimal design of heat sinks.

Multi-robot task assignment for serving people quarantined in multiple hotels during COVID-19 pandemic.

Efficiently combating with the coronavirus disease 2019 (COVID-19) has been challenging for medics, police and other service providers. To reduce human interaction, multi-robot systems are promising for performing various missions such as disinfection, monitoring, temperature measurement and delivering goods to people quarantined in prescribed homes and hotels. This paper studies the task assignment problem for multiple dispersed homogeneous robots to visit a set of prescribed hotels to perform tasks such as body temperature assessment or oropharyngeal swabs for people quarantined in the hotels while trying to minimize the robots' total operation time. Each robot can move to multiple hotels sequentially within its limited maximum operation time to provide the service. The task assignment problem generalizes the multiple traveling salesman problem, which is an NP-hard problem. The main contributions of the paper are twofold: (I) a lower bound on the robots' total operation time to serve all the people has been found based on graph theory, which can be used to approximately evaluate the optimality of an assignment solution; (II) several efficient marginal-cost-based task assignment algorithms are designed to assign the hotel-serving tasks to the robots. In the Monte Carlo simulations where different numbers of robots need to serve the people quarantined in 30 and 90 hotels, the designed task assignment algorithms can quickly (around 30 ms) calculate near-optimal assignment solutions (within 1.15 times of the optimal value). Numerical simulations show that the algorithms can lead to solutions that are close to the optimal compared with the competitive genetic algorithm and greedy algorithm.