Hasil untuk "Mechanical engineering and machinery"

Menghui Cui, Gongxue Zhang, Shaoqiang Cao

Bohao Su, Junli Sun, Dafeng Long

Lamia Benahmed, Khaled Aliane, Brahim Rostane et al.

<p>This work focuses on geothermal energy recovery using a vertical geothermal heat exchanger coupled with a heat pump for heating applications. The primary objective of this study is to conduct a 3D numerical simulation to evaluate the effects of baffles on the thermal performance of a U-shaped heat exchanger. These baffles, designed to alter flow characteristics, were implemented to enhance heat transfer and optimize overall system efficiency. The mathematical model is based on the governing equations of fluid mechanics and thermodynamics, solved using the finite volume method in the Ansys CFX software. Various baffle configurations were investigated, focusing on their placement (on the inlet and outlet tube), geometry, and the use of perforations with decreasing diameters. Simulations were conducted for a Reynolds number of Re=3600, capturing the flow behavior under specific conditions. The analysis revealed that the optimal configuration, involving baffles strategically placed on the outlet tube with decreasing perforation diameters, significantly improved thermal performance. These findings highlight the potential for designing more efficient heat exchangers in geothermal systems, paving the way for advancements in sustainable energy solutions.</p>

Zhiqiang Dai, Rungroj Chanajaree, Chengwu Yang et al.

Traditional aqueous electrolyte systems in zinc-ion batteries (ZIBs) often face challenges such as sluggish ion transfer kinetics, dendrite formation, and sudden battery failures in harsh temperature environments. Herein, we introduce a pioneering approach by integrating a bifunctional additive composed of ethylene glycol (EG) and sodium gluconate (Ga) into ZnSO4 (ZSO) electrolyte to overcome these obstacles. The polyhydroxy structures of EG and Ga can reconstruct the hydrogen bond network of H2O to improve its liquid stability, and also adjust the coordination environment around hydrated Zn2+. Additionally, Ga in the H2O–EG mixture leads to the formation of a robust protective layer that promotes uniform deposition of Zn2+ ions and minimizes unwanted side reactions. Therefore, Zn anodes with 40% ZSO–Ga electrolyte can cycle for more than 3,000 h at 25 °C and 800 h at 50 °C. Furthermore, Zn||NH4V4O10 (NVO) full batteries demonstrate remarkable cycle stability, lasting up to 10,000 cycles at 1 A g−1 with a capacity retention of 79.1%. The multifunctional electrolyte additive employed in this study emerges as a promising candidate for enabling highly stable zinc anodes under diverse temperature conditions.

Mezulis Marcis, Arbidans Lauris, Nikolajeva Vizma et al.

Timber harvesting of coniferous trees (the most abundant species in the Northern Hemisphere) leaves significant greenery side streams – coniferous needles and branches (pine, spruce and other species). Coniferous needles have been widely used in ethnomedicine, and recent research characterizes them as rich sources of biologically active compounds with immunostimulatory and anti-inflammation activities, as well as they are traditionally used to treat inflammation of the respiratory tract, colds and flu. However, new sustainable extraction methods should be proposed to obtain coniferous needle extracts with biomedical application potential. Classical extraction methods (stirring and heating) were used in this study and compared with ultrasonic treatment, and process duration and temperature optimisation were performed. During extraction, glycerol and propylene glycol, solvents widely used in the food and pharmaceutical industries, were used to improve the extracts’ stability. Obtained coniferous needle and branch extracts were characterized by their antiradical activities (17–82 % Trolox eq.) and total polyphenol concentration (6–22 % gallic acid eq.) was analysed. The extracts were tested for antibacterial and antifungal activity, which demonstrates activities comparable to synthetic drugs with potentially lower side effects caused by drugs.

A. G. Magdin, A. D. Pripadchev, A. A. Gorbunov et al.

To process agricultural crops, unmanned aerial vehicles carrying tanks with liquid chemicals are used. The paper highlights that containers made of polypropylene and polyethylene exhibit inferior qualities compared to those made of fiberglass, specifically, in terms of strength, thermal stability, resistance to ultraviolet rays, and service life. (Research purpose) To design and manufacture a tank made of composite fiberglass material with a water hammer damper. (Materials and methods) S-glass and epoxy vinyl ester resin were selected for the tank, as they exhibit superior resistance to chemical influences. To construct the tank elements, spray application, impregnation of glass fiber filler in a closed form, and winding were used. (Results and discussion) A comparative analysis was conducted on tank models, assessing their performance with and without a water hammer damper. The effectiveness of the suggested solution has been substantiated through the utilization of KOMPAS-3D software in the KompasFlow application, Within this software, the hydraulic shock is simulated to propagate inside the tank, reflecting off the walls, and gradually diminishing. Load and strength calculations for the fiberglass tank were performed by considering fiberglass parameters using the APM FEM application. (Conclusions) A tank model designed for application of liquid chemical substances in crop spraying from unmanned aerial vehicles has been developed. Innovative methods were employed in the manufacturing of the tank components. Additionally, careful consideration was given to the feasibility of maintenance and reparability. The tank’s volume (experimental sample) measures 0.0158 cubic meters, with a length of 480 millimeters, a width of 216 millimeters, a thickness of 3.6 millimeters, and a weight of approximately 4 kilograms. The design for mounting the composite tank on the unmanned aerial vehicle ensures that the weight of the unmanned aerial vehicle does not impact the tank.

Yujie Zhang, Chao Mi

AbstractAddressing the current issues of low accuracy in container positioning and posture recognition, as well as long response times during the port automation loading and unloading process, this paper designs a rapid container target recognition and measurement device and method for automated loading and unloading, thereby optimizing the acquisition of key parameters in automated loading and unloading operations. This method combines advanced convolutional neural networks and traditional image processing algorithms to achieve precise detection and tracking of container corner fittings. Furthermore, this paper proposes a high-speed response method for small target measurement, which integrates minimized deep learning network technology and fuzzy image morphology matching algorithms to enhance the accuracy and stability of corner fitting detection. Through experimental verification, this method effectively improves the speed of single detection and reduces the localization error of small targets.

Chenyu Liu, Anlin Wang, Xiaotian Li

AbstractAiming at the durability problem of the proportional electromagnet used in the proportional valve of engineering machinery, in order to improve its thermal failure resistance under random load conditions, a parametric redesign model of the proportional electromagnet was proposed based on the multi-physics coupling theory and robust optimization theory. This article takes the proportional electromagnet with a basin-type suction structure as the research object. The parameter model was verified through steady-state proportional electromagnet tests and temperature distribution tests. On the premise of ensuring the accuracy of electromagnetic calculation force, the conductivity and heat transfer parameters with fuzzy magnitude in the system were calibrated. Taking the key structural parameters of the proportional electromagnet and coil as the control factors, and the enameled wire diameter of the coil caused by the uncertainty of the production process conditions as the noise factor, an orthogonal experiment was designed based on the Taguchi method, and the thermal robustness redesign evaluation function of the proportional electromagnet was defined. Multi-factor weighted form. The thermal load of the proportional electromagnet obtained from the excavator field test was used as the response to calculate the heat source. Under the constraint of allowable temperature rise that can not cause coil insulation failure, a redesign method for key structural parameters that minimizes changes in system response under noise interference is given. Studies have shown that coil length and number of turns are the main factors affecting the thermal robustness of proportional electromagnets. The window shape of the coil is determined by the winding process and determines the magnetic properties and heat transfer capabilities of the system. The thermal robustness redesign method of proportional electromagnets proposed in this article has engineering reference value for the customized design of electromechanical products under magnetothermal coupling conditions.

Zenghui Zhu, Qingqin Meng

AbstractIn order to meet lightweight design requirement of vehicle-borne electronic chassis, vibration and impact response of chassis was analyzed based on the theory of random vibration and transient impact dynamics. Considering the influence of heat dissipation, corrosion resistance, material strength and economy of processing, weight reduction design was carried out according to vibration and impact response stress nephogram of chassis. The computation results show that the weight of chassis frame decreased by 16.4% and the first-order modal frequency of chassis decreased by 14.2% after weight reduction. Impact response had a lag relative to input impact spectrum. The increase of vibration stress was obviously higher than that of impact stress in different directions, which was still less than the corresponding material yield strength. That is, the structural strength of chassis after weight reduction meets the requirements of vibration and impact resistant design. The research results can provide theoretical basis of electronic equipment lightweight design under vehicle vibration and impact environment.

Alfisutri Khaira, Nelvi Erizon, Ambiyar Ambiyar

Beside interaction,  attitude is another factor that cause the lack of understanding in learning process. Learning attitude is needed for success and smoothness of the learning processed. The purposed of the studied was to determines the correlation between attitudes and learning outcomes and how much influence the two variables had. Quantitative research with correlation analysis is applied to find out the relationships between two variable. Result from data analysis using a hypothesis test with products moment correlations analysis obtaineds a correlations coefficient values of 0.454 with a sig value of 0.0009. From the result concludes thats theres is a relationship betweens the two variables, this happens because the value of sig < 0.005 is strengthened by the calculated r value of 0.361 and the r table value of 0.2706 meaning Ha is accept and Ho is reject whiled the value of the magnitudde of the influences betweens the two variables is 13, 06%, which means that attitude is one of the determine factor in the student learnings outcomes in this studied. The conclusions is thats there’s a positived correlation between attitudes and learn outcome of student of class X Mechanical Engineering at SMK N 5 Padang and from the result it’s known thats one of the factor in improving learning outcomes is attitude in learning. Learning outcomes can increase with a good learning attitude and vice versa.

Zeguang Li, Laiping Li, Wei Huang

AbstractAt present, for the study of the dynamic characteristics of the hydro-pneumatic suspension of vehicles, the elastic force is mainly modeled by the variable gas equation of state, and the damping force is modeled by thin-walled orifice theory, which only considers the turbulent flow. Here, based on expressing the whole flow field including laminar flow, transition flow, and turbulence with piecewise function, the turbulence region is modeled by the Brasius formula and thin-walled orifice theory respectively. By applying vibration signals collected from real roads, the responses of two piecewise function damping force models and traditional thin-walled orifice model of 1/4 suspension system in the time domain and frequency domain respectively are calculated. The average absolute error MAE and root mean square error RSME are used to compare them with the real upper fulcrum data of the suspension cylinder. The results show that different models can simulate suspension vibration well in the low-frequency range, but there are obvious deficiencies in the middle and high-frequency range, while the short-hole flow theoretical model in the form of a piecewise function is closer to the real value in the frequency domain.

Zihao Ye, Yonghang Wang, Jiasheng Yao et al.

AbstractIn order to study the influence of roughness on the nanoindentation test, finite element method was used to simulate the nanoindentation test process, and secondary indentation method was further proposed to suppress the influence of roughness on the indentation. After optimizing the indentation parameters, the relative error between the results of nanoindentation simulation for rough surface samples and smooth surface samples is stable within 5%. The secondary indentation method can effectively reduce the influence of roughness on nanoindentation test results.

Yang Gao, Jiali Ma, Qingwei Chen et al.

Abstract This paper focuses on the global prespecifiable fixed‐time control problem of uncertain strict‐feedback nonlinear system with input quantization. In contrast to the existing fixed‐time control results, the signs of the control gains can be unknown in our paper. Unlike the traditional fixed‐time control schemes, some exponential functions are added into the virtual controllers to accelerate the convergence rate. Besides, some dynamic switching functions are also introduced to compensate the unknown control signs. Based on the novel regulate law, the switching functions can be regulated online to ensure the fixed‐time stability for the considered system. Furthermore, the settling time can be easily adjusted by selecting the controller parameters. Simulation results are provided to illustrate the effectiveness of the proposed control scheme.

Ebbe Kyhl Gøtske, Gorm Bruun Andresen, Marta Victoria

Future highly renewable energy systems might require substantial storage deployment. At the current stage, the technology portfolio of dominant storage options is limited to pumped-hydro storage and Li-ion batteries. It is uncertain which storage design will be able to compete with these options. Considering Europe as a case study, we derive the cost and efficiency requirements of a generic storage technology, which we refer to as storage-X, to be deployed in the cost-optimal system. This is performed while including existing pumped-hydro facilities and accounting for the competition from stationary Li-ion batteries, flexible generation technology, and flexible demand in a highly renewable sector-coupled energy system. Based on a sample space of 724 storage configurations, we show that energy capacity cost and discharge efficiency largely determine the optimal storage deployment, in agreement with previous studies. Here, we show that charge capacity cost is also important due to its impact on renewable curtailment. A significant deployment of storage-X in a cost-optimal system requires (a) discharge efficiency of at least 95%, (b) discharge efficiency of at least 50% together with low energy capacity cost (10 €/kWh), or (c) discharge efficiency of at least 25% with very low energy capacity cost (2 €/kWh). Comparing our findings with seven emerging technologies reveals that none of them fulfill these requirements. Thermal energy storage is, however, on the verge of qualifying due to its low energy capacity cost and concurrent low charge capacity cost. Exploring the space of storage designs reveals that system cost reduction from storage-X deployment can reach 9% at its best, but this requires high round-trip efficiency (RTE≥90%) and low charge capacity cost (35 €/kW).

Poplawski Mateusz, Silva François, Vanel Jean-Charles et al.

Modulated photoluminescence (MPL) is a powerful technique for determining the effective minority carrier lifetime (τeff) of semiconductor materials and devices. MPL is based on the measurement of phase shifts between two sinusoidal waves (minimal amplitude excitation; and PL signal). In particular, in situ τeff has been proven to be an effective measurement at showing changes within a plasma-enhanced chemical vapor deposition reactor during fabrication of c-Si solar cells. However, the required time for a single measurement, using the previous method, was 40 s. In this paper a new input signal is proposed, called Dolphin's Wave, providing a method for decreasing the required measurement period to under 2 s, using superposition, frequency sweeps, and wavelets.

Chunsheng Ma, Jianguo Liu, Jie Wen et al.

The Parasitic Motion and workspace of a new 2-PRU/PUU parallel mechanism are analyzed. Firstly， the degree of freedom of the mechanism is analyzed according to the spiral theory， and then the correctness of the results is judged by the modified Grübler-Kutzbach formula. Secondly， by establishing the kinematics mathematical model of 2-PRU/PUU parallel mechanism， the mathematical relationship between the Parasitic Motion and the position and pose of the moving platform is deduced. On this basis， the inverse position solution of the mechanism is calculated using the three-dimensional space coordinate vector method. Finally， the limit boundary search method is used to calculate the workspace in Matlab software， and Adams software is used to simulate the moving platform centroid motion parameters of 2-PRU/PUU parallel mechanism. The research provides theoretical and data support for scale synthesis， error analysis and practical engineering application of the mechanism.

Ning Li, Longpeng Ding, Xianfei Wang et al.

The objective of this study was to design and optimize the pruning and crushing machinery of jujube branches, and to provide the corresponding data reference, so as to improve the cutting and crushing efficiency of jujube branches. Take fresh jujube branches (31.7±5 % w.b) as the research object. The morphology and microstructure of jujube branches were detected by scanning electron microscope. Four kinds of cutting blades were selected and manufactured, and the cutting characteristics of four kinds of blades against branches were evaluated. The shear fracture process of jujube branches was analyzed according to the microstructure of branches. Covariance analysis was used to separate the influence of water content on shear strength, and the significance level of the influencing factors is evaluated. The analysis of the test results showed that: the significant effects on shearing strength of the branches are shearing angle, cutter shape and shear speed from large to small. The force-displacement curves of cutting tool branches with different shapes of edge lines are different, and the peak of the shear force generally appears in the II&IV stages (xylem) shearing process. Under the same shear mode and the same shear velocity, the shear strength of the cambered cutter is the smallest.

Livzeniece Lasma, Pubule Jelena, Blumberga Dagnija

Early 2020 Latvian government approved the National Energy and Climate Plan 2021 – 2030 (hereinafter - NECP2030) – a long-term energy and climate planning document setting the basic principles, goals and action lines of Latvia’s national energy and climate policy for the next ten years. Although a specific target of 800 MW for wind energy development has been set, there is limited information provided on the means of achieving the wind energy target. A roadmap on wind energy development would be helpful for the stakeholders, providing a clear plan on the wind energy development, including the assessment of the most suitable form of wind energy for Latvia. The goal of this study is to propose a flexible and adaptable tool to assess, compare and select the most advantageous wind energy development alternatives for policy makers. The research goal is met by applying sustainability SWOT analysis in combination with the Multi-Criteria Decision Analysis, using the Technique for Order of Preference by Similarity to Ideal Solution. The combination of two provides a) an evaluation of comparable criteria for onshore and offshore wind energy b) assessment of the wind energy sustainability within the selected scenarios c) selection of the best possible scenario. The proposed method can help structure and lessen the complexity around the wind energy dilemma while considering economic, environment, social and technological aspects.

Xiaomei Wang, Xiaomei Wang, Yingqi Li et al.

Soft continuum robots have been accepted as a promising category of biomedical robots, accredited to the robots’ inherent compliance that makes them safely interact with their surroundings. In its application of minimally invasive surgery, such a continuum concept shares the same view of robotization for conventional endoscopy/laparoscopy. Different from rigid-link robots with accurate analytical kinematics/dynamics, soft robots encounter modeling uncertainties due to intrinsic and extrinsic factors, which would deteriorate the model-based control performances. However, the trade-off between flexibility and controllability of soft manipulators may not be readily optimized but would be demanded for specific kinds of modeling approaches. To this end, data-driven modeling strategies making use of machine learning algorithms would be an encouraging way out for the control of soft continuum robots. In this article, we attempt to overview the current state of kinematic/dynamic model-free control schemes for continuum manipulators, particularly by learning-based means, and discuss their similarities and differences. Perspectives and trends in the development of new control methods are also investigated through the review of existing limitations and challenges.

Jingdong Zhang, Kuan Yang, S. Zhao et al.

Gear transmission is one of the most common mechanical transmissions in contemporary machinery. It is the main form of transmission of mechanical power and movement, and it is an important part of all kinds of machinery. For gear transmission, better hardness and wear resistance are required, which can be achieved by quenching process. But the spur gear in quenching process, its size and shape will appear different degree of deformation, this paper uses the Pro/Engineering software to establish solid parameterized model of the spur gears. Then, the simplified single tooth solid model of the spur gear imported to ANSYS software to obtain the finite element model. The temperature field of the single tooth spur gear during quenching were carried out. Thus, it is concluded that the relationship between the factors influencing the quenching. The results provide a certain reference basis for the establishment of the hot working processes of the spur gear.