Ideal Working Conditions Research Articles

Investigation of hot deformation behavior and microstructure evolution of TC18 alloy and establishment of constitutive equation under friction-temperature correction

The effects of deformation temperature and strain rate on the microstructure evolution of TC18 alloy are studied by hot compression experiment and EBSD test, based on the double correction of friction and temperature rise in hot compression, a more accurate constitutive equation and thermal processing diagram are established. Recrystallization grain is the main microstructure of TC18 alloy during deformation from 810 °C to 930 °C. Higher deformation temperature and lower strain rate are beneficial to the occurrence of dynamic recrystallization and grain size growth. The strain rate has no significant effect on volume fraction of large and small angle boundary. After double correction of temperature rise and friction, it is found the activation energy of TC18 titanium alloy in β region and α/β region are 485.895 kJ/mol and 355.337 kJ/mol, respectively. The ideal hot working conditions of TC18 titanium alloy are 812 °C ∼ 840 °C, 0.01 s−1 ∼ 0.018 s−1 and 878 °C ∼ 915 °C, 0.178 s−1 ∼ 1.0 s−1, respectively. The unevenness of microstructure, the large size difference among grains and the large orientation difference among grains lead to the instability of hot working process. The conclusions of this paper can provide more accurate guidance for the determination of hot working parameters and the prediction of microstructure evolution during hot working of TC18 alloy.

A novel stepwise microwave hydrodistillation and extraction process for separating seed oil and essential oil simultaneously from perilla seeds

Stepwise microwave hydrodistillation and extraction (SMHDE) was utilized to separate perilla essential oil as a byproduct while boosting perilla seed oil yield and quality. The optimal process for producing perilla seed oil was determined by Plackett–Burman and Box–Behnken design experiments based on a factor screening experiment. Under ideal working conditions, the yield of seed oil was 36.49% ± 0.07%. The content of α-linolenic acid in perilla seed oil obtained by SMHDE was 69.90%, which was significantly greater than that obtained by Microwave-assisted method (MAE) (66.59%) and that obtained by Soxhlet extraction (SE) (66.51%). The yield of perilla seed essential oil obtained by SMHDE was 0.55 ± 0.14 mL/kg, and the main component was perillaldehyde, which was present at a concentration of 20.50%. GC‒MS analysis revealed that the content of volatile compounds in seed oil obtained by SMHDE (9.20%) was significantly lower than that obtained by MAE (10.94%) and SE (15.23%). Compared with traditional methods, SMHDE can effectively increase seed oil yield and quality without negatively influencing its fatty acid composition or physicochemical properties. These findings support the use of SMHDE to increase the production and quality of seed oil and prevent the waste of perilla essential oil resources.

Experimental analysis of slewing energy recovery potential of large hydraulic excavator

Large hydraulic excavators, characterized by large inertia of slewing movement, frequent accelerating and braking, have ideal working conditions for energy recovery and reuse. This paper investigates the slewing energy-saving potential of large hydraulic excavators via experiments conducted under different working conditions. Firstly, the working principle and energy flow of the slewing system of the hydraulic excavator are analyzed, and the evaluation indexes for energy-saving potential are proposed. Additionally, a 50 ton slewing experimental prototype is established, and comparative experiments are conducted. The energy flow analysis demonstrates that the energy loss due to slewing overflow is the primary factor for the low energy utilization rate of the slewing system. Finally, the influence of engine speed, slewing angle, and load on the potential of slewing energy recovery are analyzed. The experiential results reveal that the energy-saving contribution rates of accelerating and braking range from 42% to 45.36% while the energy regeneration rate is 56% under the single-action condition. And the comprehensive contribution rate of accelerating and braking energy is about 9.2% under the compound-action working condition, which has a significant energy-saving potential.

The employing of pure calcium sulfate extracted from phosphogypsum for composing highly pure ammonium sulfate and calcium carbonate

ABSTRACT The phosphoric acid wet process waste stream provided the phosphogypsum (PG). Phosphogypsum waste is environmentally harmful and economically valuable. However, processing phosphogypsum to produce (NH4)2SO4 and CaCO3 can solve these environmental and economic issues. ICP-OES, XRD, SEM-EDS, FTIR, and TGA were used to characterize PG, purified CaSO4, (NH4)2SO4, and CaCO3. Herein, PG is treated with different HNO3 concentrations and 0.5M NH4NO3 to eliminate most impurities for gaining a highly purified CaSO4. The factors affecting CaSO4 purification were studied. These aspects include HNO3 and NH4NO3 concentration, the S/L ratio, time spent on treatment, temperature, and grain size. According to the findings, the ideal working conditions for extracting 98.71% of CaSO4 from PG are as follows: 149 µm grain size, 0.5M NH4NO3, 2M HNO3, 1/4 S/L, 30 minutes reaction time, 300 rpm, and 80°C. Using a pure CaSO4 suspension as the raw material, CO2, and a mechanical stirring method, the (NH4)2SO4 solutions crystallized by heating and CaCO3 precipitate were investigated through several trials. The preparation method was investigated by changing variables such as the NH4 +/Ca2+ molar ratio, reaction time, CO2 flow rate, and temperature. Finally, (NH4)2SO4 (98.25%) and CaCO3 (98.5%) are produced from the slurry of pure CaSO4.

Improved Performance of the Integrated Power Supplies Based on Cu2ZnSn(S,Se)4 Solar Cells

Solar energy is an environmental friendly and sustainable energy source to solve the energy shortage and environmental pollution problems nowadays. Integrated power supply shows great potential in utilizing solar energy which converts solar energy into electrical energy. Integrated power supplies with optimized structures are constructed with Cu2ZnSn(S,Se)4 solar cells and LiFePO4 (LFP) lithium‐ion batteries for the first time. The matching of integrated power supply is investigated in detail for a better understanding and design of highly efficient integrated power supply. In the results, it is shown that the open‐circuit voltage of solar cells has a significant influence on the efficiencies of integrated power supply. Apart from that, the calculation of average power coupling factor is proved to be an effective method to evaluate the difference between the actual and ideal working condition of the integrated power supply. As to current matching of integrated power supply, it is emphasized that the capacities of LFP coin cells should be designed within a normal range where the photo‐charging time and the characteristic of energy‐storage batteries need to be considered simultaneously.

Role Identities in Colombian Music Education Graduates

The tension between performer and teacher identities in music education is a widely recognized phenomenon within the profession. However, in Colombia, previous research has mainly focused on curricular evaluations, profile, and labor market conditions, leaving a significant gap in our understanding of identity. This study aimed to investigate the role identities among graduates of the Adventist University Corporation. Two focus groups were conducted to explore the existing condition of teacher and performer identities and the impact of government-mandated curricular modifications on recent graduates’ teacher identity. The results revealed a persistent dichotomy among participants in their working lives despite institutional efforts. The major causes of identity imbalance were less than ideal working conditions in public schools, hidden curricula, and career breadth. To address these issues, future governmental and institutional endeavors should focus on improving working conditions, adapting curricula to the labor market, and providing active support for teacher identity based on experiences.

Characteristic research of regeneration process of particulate filter medium in vibrated fluidized bed

Abstract The vibrational fluidized bed is innovatively adopted to regenerate the particulate filter medium for the purification of crude synthesis gas from the coal gasification process. Characteristic research of vibrated fluidized beds during dust-containing particulate filter medium regeneration has been carried out. The ideal transport model of particulate filter medium on the distributor is established and verified by using experiments. The mean residence time of the particulate filter medium can be reduced by 72% from 5.5 to 1.5 min with an increase in the working frequency from 50 to 60 Hz. The thickness of the bed layer is linearly increased with the feeding rate of the particulate filter medium under ideal working conditions. The resistance models of the fluidizing air are built up and validated, and they can be used to calculate the pressure drop of the static bed layer of the particulate filter medium on the fluidizing air distributor, which is the maximum value of the dynamic bed layer with the same thickness. The fluidizing air makes the mean residence time of the particulate filter medium decrease by 50% and reduces the difference in the particulate mean residence time under different feeding-rate conditions. The regeneration effect of dust-containing filter medium particles in a vibrated fluidized bed is evaluated. Fluidizing air with superficial velocity ranging from 0 to 0.6~0.9 m·s–1 makes the regeneration efficiency increase from 29.41% to 70.59~88.24%. This article provides a reference for the industrial application of a vibrated fluidized bed for the particulate filter medium recycling system.

Operational optimization of copper flotation process based on the weighted Gaussian process regression and index-oriented adaptive differential evolution algorithm

Concentrate copper grade (CCG) is one of the important production indicators of copper flotation processes, and keeping the CCG at the set value is of great significance to the economic benefit of copper flotation industrial processes. This paper addresses the fluctuation problem of CCG through an operational optimization method. Firstly, a density-based affinity propagationalgorithm is proposed so that more ideal working condition categories can be obtained for the complex raw ore properties. Next, a Bayesian network (BN) is applied to explore the relationship between the operational variables and the CCG. Based on the analysis results of BN, a weighted Gaussian process regression model is constructed to predict the CCG that a higher prediction accuracy can be obtained. To ensure the predicted CCG is close to the set value with a smaller magnitude of the operation adjustments and a smaller uncertainty of the prediction results, an index-oriented adaptive differential evolution (IOADE) algorithm is proposed, and the convergence performance of IOADE is superior to the traditional differential evolution and adaptive differential evolution methods. Finally, the effectiveness and feasibility of the proposed methods are verified by the experiments on a copper flotation industrial process.

Uber structure's managerial algorithmic communication and drivers' health issues: sensemaking of work strategic resistance

This article focuses on the role that algorithms play as a communicative infrastructure that contributes to poorer occupational health in the gig economy by interviewing 50 Uber drivers based on the life-story methodological approach. Specifically, the paper draws attention to Uber structure's managerial algorithmic communication and its effects on drivers' occupational health by engaging with Giddens's theoretical framework of structure-agency and Weick's theory of sensemaking. Furthermore, the study also explores the different factors contributing to the construction of individual and collective resistance of drivers to Uber's monopoly. The findings reveal that Uber's structure imprisons the users' freedom of negotiation and action, which creates a stressful work environment as managerial algorithmic communication only functions effectively in ideal working conditions, while abnormality is very frequent in a profession like transportation. Driver agency consists of organizing individual and collective resistance to change Uber's work decisions and weaken them. On an outside platform, resistance strategies are deployed by drivers to pressure Uber, with the goal of protecting their occupational health.

Study on human-SRL synchronized walking based on coupled impedance.

Supernumerary robotic limbs (SRL) is a novel category of wearable robotics. Unlike prostheses (compensation for human limbs) and exoskeletons (augmentation of human limbs), SRL focuses on expanding human limbs and enhancing human activities, perception, and operation through the mutual collaboration of mechanical limbs and human limbs. The SRL of lower limbs are attached to the human waist, synchronized with the human walking in the forward direction, and can carry weight independently in the vertical direction. In order to enhance the synchronization performance of the human-machine system during walking and minimize interference with human gait, it is essential to investigate the coupling dynamics within the human-SRL system. To facilitate our research, this paper focuses on relatively ideal working conditions: level road surfaces, no additional weight-bearing on the SRL, and humans walking in a straight line without any turns. We build upon the passive dynamic walking theory and utilize the human-SRL system model established by MIT to develop a coupling system model. Through numerical simulations, we identify the optimal values for the stiffness and damping coefficients of the human-machine connection. Additionally, we have designed the wheel-legged SRL structure and constructed the SRL control system for experimental validation. It is found that a better synchronization of the human-machine walking process can be achieved by configuring suitable spring and damping units in the human-machine connection part. In this study, we explored the concept of SRL and its potential benefits for enhancing human motion, conducting simulations and experiments based on the coupled dynamics of human-SRL systems. The results indicate that by equipping the human-machine connection component with suitable spring and damping units, synchronization during the walking process can be improved.

Nitrate-mediated kinetic leaching for rare earth elements recovery from phosphogypsum

Phosphogypsum (PG) is a byproduct of the decomposition of phosphate rock with sulfuric acid during phosphoric acid synthesis. Various techniques such as X-ray diffraction (XRD), Scan electron microscope with electron dispersive spectroscopy (SEM-EDS), Fourier-transform infrared spectroscopy (FTIR), and Thermal gravimetric analysis (TGA) are utilized to characterize PG and rare earth concentrate. Heir, both nitric acid (HNO3) and ammonium nitrate (NH4NO3), are used as leaching agents for rare earth elements (REEs) from Egyptian PG. The ideal working conditions for leaching about 85% of REEs from PG are 350 mg/kg REEs in PG, 149 μm grain size, 0.5M NH4NO3, 2M HNO3, 1/4 S/L, 30 minutes leaching time, 300 rpm, and 80°C. The data on the kinetic REEs leaching are matched to the diffusion control model. The kinetics of the applicable leaching activity and the reaction mechanism between the mixture of nitric acid and ammonium nitrate with REEs have been explored in detail. After concentration by vaporization to one liter, a final concentration of REEs reached ≈ 300 mg/L with a leachability of 85%. The REEs were precipitated using 20% oxalic acid at pH 2.5 as oxalate, and then the precipitate was calcined at 900°C in an electric oven, given a mixture of REEs oxides and CaO.

Design of three-roll bending machine tool and research on compensation algorithm

With the rapid development of profile processing industry, the processing shape, efficiency, and consistency of profiles are more and more demanding. In this case, the progress of bending machine tools was very important. In this study, the disadvantages and shortcomings of traditional three-roll bending machine are investigated, and a new design of three-roll bending machine is proposed, including a new mechanical structure, hydraulic pressure, and control system. ABAQUS was used to analyze the constrained mode of the table, and the first six order natural frequencies and natural vibration modes were obtained. A mathematical model was established to analyze the relationship between the pressure displacement and the forming radius under ideal working conditions, and the limit position of the downward movement of the lower press roll and the speed relationship between the lower press roll and the support roll are discussed. Based on the experimental data, the nonlinear curve fitting was carried out on the rebound compensation algorithm of asymmetric rolling bending forming. The fitting rebound compensation algorithm was carried out on the symmetric rolling bending forming experiment. The experimental results show that this algorithm can be applied to both symmetric rolling bending and asymmetric rolling bending.

Pyrolysis of Mixed Date Stones and Pistachio Shells: Identification of Bio-Oil and Utilization of Bio-Char as Activated Carbon Precursor.

Thermal pyrolysis of mixed date stones and pistachio shells in a semi-batch reactor was addressed in this study. The highest yield of liquids (51.20 %) was produced at 500 °C, 90 min, 20 °C/min heating rate, and 50 mesh particle size. Under these conditions, yield of liquid from date stones and pistachio shells separately was 49.12 % and 47.67 %, respectively. The FT-IR results confirmed the presence of multiple oxygen-containing compounds in the bio-oil. Results from GC-MS declared that it was predominately composed of acids (57.57 %), esters (21.35 %), phenols (4.63 5), and alcohols (3.49 5). The obtained biochar was transformed into activated carbon (AC) by the optimized ZnCl2 activation method. The ideal AC was synthesized at 600 °C for 60 min using a 2 : 1 ZnCl2 : biochar impregnation ratio. FESEM and XRD measurements showed that the AC was amorphous. The prepared AC was effective in eliminating dibenzothiophene (DBT) from model fuel (200 ppm DBT/hexane) with a maximum performance 95.26 % at 40 °C for 1h using 0.35 g of the AC. The exhausted AC was regenerated and reutilized 4 times, and removal efficiency reached 88.23 % in the 4th cycle under ideal working conditions.

An artificial neural network-particle swarm optimization (ANN-PSO) approach to predict the aeration efficiency of venturi aeration system

In the present study, the artificial neural network-particle swarm optimization (ANN-PSO) approach was adopted for optimizing the standard aeration efficiency (SAE) of the venturi aeration system. Standard aeration efficiency (SAE) is the main parameter which is used to evaluate the effectiveness of an aerator. Aeration test were carried out in a 220 litre capacity tank to find out the impacts of operating variables on SAE using venturi aeration system. The operating variable includes throat length (L), hole diameter (d), and flow rate (Q), however, the output variable was selected as SAE to determine the model response. A 3-6-1 ANN model was developed for predicting the SAE of venturi aeration system, and the PSO algorithm was applied to obtain the optimum values of the operating variables of venturi aeration system. The effectiveness of the ANN modelling was evaluated using the coefficient of determination (R2), root mean square error (RMSE), and mean absolute error (MAE) from the test data and forecasted data. The most appropriate optimal values of the operating variables i.e., L, d, and Q were found to be 1.82 mm, 2.00 mm, and 0.31 l/s, respectively. The optimal SAE under ideal working conditions was optimized to be 0.8333 kg O2/kWh. The applied ANN-PSO approaches can predict the optimal values satisfactorily with a maximum of 7.73% difference with the experimental values. Therefore, the suitability of the ANN-PSO approach can be useful to predict the aeration efficiency of venturi aeration system.

Analyzing the pressure and thermal efficiency of chemically synthesized nanofluids for computer cooling methods

To maintain ideal working conditions by removing heat, a particular technique must be applied. This research examines how nanofluids affect computer cooling microchannel heating devices. The experiment's working fluids are 25% Therminol-55 and 75% sprinkling water. The mixture contains silicon carbide (SiC), titanium oxide (TiO2), and zinc oxide (ZnO) nanoparticles. It includes 0.25% to 1.5% nanoparticles and flows at 0.025 to 0.080 kg/s at 25°C to 40°C. Central processing unit temperature, heat transfer rate, pressure losses, and pumping power have been examined. SiC-THERMINOL/SPRINKLING WATER at 1.5% concentration and 0.080 kg/s had a 9% lower temperature and 31% larger heat transfer coefficient than the base fluid. SiC-TL/SW has the highest pressure decrease and pumping force power compared to TiO2-TL/SW. Because nanofluid beats basic fluid in computer cooling, a little increase in pumping force power and pressure reduction may be tolerated.

Study on current sharing characteristics of multi-column parallel arresters

The ideal working conditions of a multi-column parallel arrester is to share the energy generated when it is impacted, otherwise it will lead to a breakdown of the arrester and the forced shutdown of the HVDC system, resulting in significant economic losses. This paper analyzes the current sharing characteristics of multi-column parallel arresters under different current waveforms, different current amplitudes, different temperatures, and different cumulative impulse times. The results show that the current waveform, current amplitude, and temperature difference between the columns all affect the current sharing characteristics. The current deviation coefficient is positively correlated with the current wave head time. The closer the current value is to the balancing point, the smaller the deviation coefficient. The temperature difference between the columns has the greatest influence on the current deviation coefficient. As the temperature difference increases, the current deviation coefficient may exceed 10%. Finally, based on experimental conclusions, some suggestions are put forward to modify the operation rules of large-capacity multi-column parallel arresters, which provides an important reference for subsequent projects.

Research on Multi-objective Optimization of Freight Train Operation Process Based on Improved Bald Eagle Search Algorithm

<p>To study the optimization problem of freight train operation process under complex line conditions, this paper adopts the freight train multi-particle model to establish the multi-objective optimization model of the freight train. Aiming at the problem of difficult optimization caused by complex line conditions, a two-step method is used to find the optimal operation strategy of the freight train. Firstly, the greedy algorithm is used to select the optimal working condition sequence. Secondly, the multi-objective optimization algorithm is used to obtain the position of the ideal working condition transition point. By introducing the idea of non-dominated sorting, an improved multi-objective bald eagle search algorithm is proposed to optimize the operation process of freight trains. This algorithm adopts the evolution method of combining bald eagle population renewal with adaptive Gaussian mutation, and introduces preference information to increase the rationality of population evolution. The simulation results show that the optimal operation strategy of freight train selected by two-step method is in line with the actual operation situation, and the proposed multi-objective bald eagle search algorithm considers both convergence and distribution. The results can satisfy the preference of decision-makers, which can provide a reference target speed curve for railway workers.</p> <p> </p>

Study on Optimization of Pump Shaft Transmission System of Plastic Centrifugal Pump

At present, the design of the pump shaft transmission system mostly refers to the design method of the metal pump transmission system. The dynamic and static characteristics of the plastic centrifugal pump are not related to the structural parameters of the pump shaft. Aiming at the influence of the structural parameters of the pump shaft transmission system on the dynamic and static performance of the plastic centrifugal pump, the three-dimensional model of the impeller and volute chamber was drawn by Creo5.0. The CFD calculation of the load of the plastic centrifugal pump was carried out. The flow field of the plastic centrifugal pump under ideal working conditions was simulated by ANSYS FLUENT. Combined with the application principle of singular function in mechanics, the mathematical model of a deflection of the pump shaft transmission system was constructed. Considering the minimum deflection and the maximum critical speed of the first order as the objective function, an optimization model of the structural parameters of the pump transmission system was established. The NSGA-II multiobjective optimization method was used to solve the optimal structural parameters of the optimization model, and the optimization design of the pump shaft span, cantilever, front, and rear bearing clearance was completed. The optimal span cantilever ratio of the rotor model of the single span cantilever structure was 1:0.75. Compared with the traditional design model, the optimized pump shaft deflection is reduced by 52.35%, and the first-order critical speed is increased by 42.77%. Simultaneously, using polynomial fitting as a mathematical tool, the experimental data were analyzed, and the mathematical expression of the rotation speed deflection relationship of the pump shaft at the first critical rotation speed and the corresponding function curve was obtained.

Health Condition Monitoring and Control of Vibrations of a Rotating System through Vibration Analysis

This paper presents condition monitoring, fault detection, and control of vibration of a rotating system using vibration analysis. The system includes ball bearings, pulleys, impellers, shafts, and an electric motor. The experimental approach generated different levels and forms of vibration that were measured using a vibration analyzer (CSI 2140). A vibration analyzer is used for determining the characteristics and nature of vibration of the experimental system. System vibrations were measured in terms of amplitude, phase angle, and frequency during the experimental operating conditions. After that, the experimental results were compared with the ideal working conditions mentioned in the ISO standard for the determination of machine health and condition monitoring. This paper also presents a passive control technique to enhance the machine’s health condition. The generated faults of the system have been detected and solved by using an exact measurement of polar plot analysis. This approach of condition monitoring, fault detection, and improving operating conditions can be used to visualize and analyze vibration data in any rotating system. Furthermore, this technique would be a feasible and effective way of finding strategies for the maintenance of rotary machines.

Work Engagement, Work Environment, and Psychological Distress during the COVID-19 Pandemic: A Cross-Sectional Study in Ecuador.

Work environments can interfere with the mental health of workers as generators or reducers of psychological distress. Work engagement is a concept related to quality of life and efficiency at work. The aim of this study was to find the relationship between work environment factors and work engagement among the Ecuadorian general population during the first phase of the COVID-19 pandemic to assess their levels of psychological distress. For this purpose, a cross-sectional, descriptive study using a set of questionnaires was performed. Sociodemographic and work environment data, work engagement (UWES-9 scale) scores, and General Health Questionnaire (GHQ-12) scores were collected. The variables that predicted 70.2% of psychological distress during the first phase of the pandemic were being female, with a low level of vigour (work engagement dimension), being stressed at work, and low job satisfaction. The sample showed an intermediate level of engagement in both the global assessment and the three dimensions, being higher in those without psychological distress. With effective actions on work environment factors, mental health effects may be efficiently prevented, and work engagement may be benefited. Companies can reduce workers’ psychological distress by providing safe and effective means to prevent the risk of contagion; reducing the levels of work conflict, work stress, or workload; and supporting their employees with psychological measures in order to maintain ideal working conditions.