Hasil untuk "Mechanical engineering and machinery"

Tejaswini Gautam, Anirbid Sircar, Kriti Yadav et al.

Bhimband, located in Bihar in eastern India hosts a well-known geothermal system that appears to be strongly influenced by fault-controlled circulation, and the surface springs there routinely reach temperatures of about 60-65 °C. In this research, the geothermal environment was analyzed using a combination of geological observations and a number of geophysical surveys, including gravity, magnetic, and electrical resistivity surveys to gain a better understanding of the subsurface environment and heat flow characteristics. Using these data, a probabilistic volumetric assessment was carried out through Monte Carlo simulations and the results indicate that the region may store on the order of ∼6.50 × 1014J of thermal energy out of which roughly ∼9.76 × 1013 J could realistically be recovered. Based on these findings, a preliminary field development strategy was outlined for a small-scale binary power plant (∼3.1 MW) operating on an Organic Rankine Cycle and designed for a 20-year life. The plan suggests a phased drilling program of 24 wells which includes exploration, appraisal, production and reinjection wells, arranged in a manner that would allow long-term and balanced extraction of heat. The revised economic analysis estimates a CAPEX of ₹86.5 crore and OPEX of ₹45 crore over 20 years, resulting in a simple payback period of ∼20 years and an IRR of ∼8%, reflecting the high upfront investment and modest project scale. The environmental factors were incorporated into the design with a focus on reinjecting the cooled fluid to maintain the reservoir pressure and minimize surface emissions. On the whole, the assessment tends towards the technical feasibility of geothermal power production at Bhimband and provides a useful initial framework for sustainable geothermal development in India, in the wake of the country's increasing interest in clean energy alternative.

Hajime Miyashita, Yuya Ito, Kenta Shinha et al.

Traditional pre-clinical drug evaluation methods, including animal experiments and static cell cultures using human-derived cells, face critical limitations such as interspecies differences, ethical concerns, and poor physiological relevance. More recently, microphysiological systems (MPSs) that use microfluidic devices to mimic in vivo conditions have emerged as promising platforms. By enabling perfusion cell culture and incorporating human-derived cells, MPSs can evaluate drug efficacy and toxicity in a more human-relevant manner. However, standard MPS protocols rely on discrete medium changes, causing abrupt changes in drug concentrations that do not reflect the continuous pharmacokinetics seen in vivo. To overcome this limitation, we developed a Dialysis Membrane-integrated Microfluidic Device (DMiMD) which maintains continuous drug concentrations through selective medium change via a dialysis membrane. The membrane’s molecular weight cut-off (MWCO) enables the retention of high-molecular-weight drugs while facilitating the passage of essential low-molecular-weight nutrients such as glucose. We validated the membrane’s molecular selectivity and confirmed effective nutrient supply using cells. Additionally, anticancer drug efficacy was evaluated under continuously changing drug concentrations, demonstrating that the DMiMD successfully mimics in vivo drug exposure dynamics. These results indicate that the DMiMD offers a robust in vitro platform for accurate assessment of drug efficacy and toxicity, bridging the gap between conventional static assays and the physiological complexities of the human body.

Emanuel Marquez-Acosta, Victor De-León-Gómez, Victor Santibañez et al.

In this paper, for the first time, experimental tests of complete offline walking gaits generated by the essential model are performed. This model does not make simplifications in the dynamics of the robot, and its main advantage is the definition of desired Zero Moment Point trajectories. The designed gaits are implemented in the NAO robot, where starting and stopping stages are also included. Simulations in MATLAB and Webots, and experiments with the real robot are shown. Also, important remarks about the implementation of walking trajectories in the NAO robot are included, such as dealing with the hip joint shared by both legs. A comparison between the linear inverted pendulum (LIP) model and the essential model is also addressed in the experiments. As expected, the robot fails following the offline gait generated by the LIP model, but it does not with the essential model. Moreover, in order to push the boundaries of the essential model, a complex gait is designed with a vertical motion of the center of mass and an abrupt movement of the arms. As shown in experiments, no external balance controller is required to perform this complex gait. Thus, the efficiency of the essential model to design stable open-loop complex gaits is verified.

Sassi Rekik, Souheil El Alimi

Renewable energy systems have emerged as a viable option to mitigate the environmental impacts of traditional fossil fuels. However, the intermittent nature of these renewables, such as solar and wind, makes it challenging to ensure a stable energy supply using only one type. Therefore, combining more than a single technology offers significant advantages in addressing the limitations associated with each individual system. Nevertheless, developing these systems requires substantial financial investments, making it crucial to identify the most suitable locations prior to installing them. In this article, the prime objective was to propose a preliminary evaluation of land suitability for constructing solar and wind hybrid facilities (PV–wind, PV–CSP, and CS–wind) in Tataouine, southern Tunisia. To this end, a GIS-based MCDA methodology was developed based on an extensive literature review and experts’ feedback while considering climate, topography, accessibility, and environmental factors. The results obtained revealed that the optimal area for a CSP–PV hybrid system is about 793 km 2 , indicating that this combination has the highest potential in terms of available resources and compatibility. On the other hand, well-suited locations for hosting CSP–wind and PV–wind systems covered areas of 412 and 333 km 2 , respectively. Such specific locations are capable of generating an annual technical potential of 316.169, 91.252, and 62.970 TWh for CSP–PV, CSP–wind, and PV–wind, respectively. Interestingly, comprising almost all of the most appropriate sites, Remada and Dhiba stand as the ideal locations for accommodating such hybrid systems. Considering this outcome, Tataouine can position itself as a model for renewable energy adoption in Tunisia. Therefore, it is imperative for policymakers, investors, and local communities to collaborate and embrace these hybrid systems to capitalize on this immense potential and pave the way for a greener and more prosperous future.

Hayat Abdulla Yusuf, Abeer Faisal Abdulla, Fatema Aqeel Radhi et al.

Biodiesel as a renewable and environmentally friendly fuel can be considered an alternative to fossil fuel in industries, and one of the promising approaches to developing biodiesel yield is its production in microreactors. However, the produced quantity from microreactors is limited which necessitates higher throughput microreactors to be produced, maintaining the high yield of biodiesel. Therefore, this study investigated the transesterification of waste cooking oil (WCO) with methanol in the presence of sodium hydroxide as the catalyst using a novel branched microreactor, used for higher throughput applications. Thus, a novel four-micro serpentine-based microreactor was designed and fabricated with no external tubing. Biodiesel is produced in the fabricated microreactor and the Box-Behnken Design method (BBD) in Minitab software was used to design the experiments with different operating conditions: methanol to oil molar ratio (6:1–12:1), catalyst concentration (0.5–1.5 wt%), and reaction temperature (55–65 °C) to optimize the biodiesel volume yield in the designed microreactor. The optimum biodiesel yield using GC–MS analysis was found to be 82.8 % at a methanol to oil molar ratio of 12:1, 1.5 wt% catalyst concentration, and reaction temperature of 59.4 °C while maintaining the reactants’ inlet flow rate of 20 µL/s. Production of up to 35 mL biodiesel was collected in 30 min only. In addition, the microreactor achieved up to 97 % conversion at inlet flow rates of 8.5 µL/s.

Songfei Su, Yang Wang, Lukai Zheng et al.

In this work, a focused ultrasonic radiator is proposed for cooling the electrical heating elements in the focal region, and its working characteristics are investigated. The analyses of the FEM computational and flow field visualization test results indicate that focused ultrasound can generate forced convective heat transfer by the acoustic streaming in the focal region, which can cool the heating elements effectively. Experiments show that when the input voltage is 30Vp-p and the ambient temperature is 25 °C, the focused ultrasonic radiator can cause the surface temperature of the heating element (high-temperature alumina ceramic heating plate with a diameter of 5 mm) in the focal region to drop from 100 °C to about 55 °C. When the diameter of the electrical heating element is changed from 5 mm to 30 mm, the cooling effect is similar in the focal region. Compared with a fan, the focused ultrasound radiator has a shorter cooling time and a more concentrated cooling area. The focused ultrasonic radiator proposed in this work is suitable for some special environments.

Taylan Atakuru, Fatih Kocabaş, Niccolò Pagliarani et al.

There has been a notable focus on the adoption of jamming-based technologies, which involve increasing the friction between grains, layers, or fibers to achieve variable stiffness capability in soft robots. Additionally, magnetorheological elastomers (MREs) that show magnetic-field-dependent viscoelasticity have great potential as a material for varying stiffness. This study proposes a hybrid method (magnetic jamming of MRE fibers) for enhancing the stiffness of soft robots, combining a jamming-based with a viscosity-based method. First, a fiber jamming structure is developed and integrated into a soft robot, the STIFF-FLOP manipulator, to prove the concept of the magnetic jamming of MRE fibers. Then, based on the proposed method, a variable stiffness device actuated by electro-permanent magnets is developed. The device is integrated into the same manipulator and the electronically controlled magnetic jamming and stiffening of the manipulator is demonstrated. The experimental results show that stiffness gain in bending and compression is achieved with the proposed method. The outcomes of this investigation demonstrate that the proposed hybrid stiffening technique presents a promising avenue for realizing variable and controllable stiffness in soft robots.

Tao Wang, Jinchun Song

The electro-hydraulic servo system has advantages such as high pressure, large flow, and high power, etc., which can also realize stepless regulation, so it is widely used in many engineering machineries. A linear model is sometimes only a simple approximation of an idealized model, but in an actual system, there may be nonlinear and transient variation characteristics in the systems. Coupling is reflected in the fact that the components or functional structures implemented by each system used for the design of hydraulic systems are not completely or independently related to each other, but affect each other. The nonlinear clearance between the actuator and the load reduces the control accuracy of the system and increases the impact, thus losing stable working conditions. In the paper, based on the nonlinear clearance problem of the electro-hydraulic servo system, a mathematical transfer model with clearance is established, and on this basis, a clearance compensation method based on the Hopfield neural network is proposed. In this way, clearance compensation can be realized by adjusting the parameters of neural network nodes, through simple and convenient operation. Finally, by setting different clearance values, the results of the step response and sine response curve before and after clearance compensation of the hydraulic system are compared, and the effectiveness of Hopfield neural network compensation clearance control is verified based on the comparison simulation results.

Yue Yu, Yao Luo, Jan Cilliers et al.

Electrostatic traveling wave (ETW) methods have shown promising performance in dust mitigation of solar panels, particle transport and separation in in situ space resource utilization, cell manipulation, and separation in biology. The ETW field distribution is required to analyze the forces applied to particles and to evaluate ETW design parameters. This study presents the numerical results of the ETW field distribution generated by a parallel electrode array using both the charge simulation method (CSM) and the boundary element method (BEM). A low accumulated error of the CSM is achieved by properly arranging the positions and numbers of contour points and fictitious charges. The BEM can avoid the inconvenience of the charge position required in the CSM. The numerical results show extremely close agreement between the CSM and BEM. For simplification, the method of images is introduced in the implementation of the CSM and BEM. Moreover, analytical formulas are obtained for the integral of Green’s function along boundary elements. For further validation, the results are cross-checked using the finite element method (FEM). It is found that discrepancies occur at the ends of the electrode array. Finally, analyses are provided of the electric field and dielectrophoretic (DEP) components. Emphasis is given to the regions close to the electrode surfaces. These results provide guidance for the fabrication of ETW systems for various applications.

Jingke Song, Jun Wei, Bin Yu et al.

Abstract Aiming at the problem that the existing ankle rehabilitation robot is difficult to fully fit the complex motion of human ankle joint and has poor human-machine motion compatibility, an equivalent series mechanism model that is highly matched with the actual bone structure of the human ankle joint is proposed and mapped into a parallel rehabilitation mechanism. The parallel rehabilitation mechanism has two virtual motion centers (VMCs), which can simulate the complex motion of the ankle joint, adapt to the individual differences of various patients, and can meet the rehabilitation needs of both left and right feet of patients. Firstly, based on the motion properties and physiological structure of the human ankle joint, the mapping relationship between the rehabilitation mechanism and ankle joint is determined, and the series equivalent model of the ankle joint is established. According to the kinematic and constraint properties of the ankle equivalent model, the configuration design of the parallel ankle rehabilitation robot is carried out. Secondly, according to the intersecting motion planes theory, the full-cycle mobility of the mechanism is proved, and the continuous axis of the mechanism is judged based on the constraint power and its derivative. Then, the kinematics of the parallel ankle rehabilitation robot is analyzed. Finally, based on the OpenSim biomechanical software, a human-machine coupling rehabilitation simulation model is established to evaluate the rehabilitation effect, which lays the foundation for the formulation of a rehabilitation strategy for the later prototype.

Maxime Berger, Ilhan Kocar, Evangelos Farantatos et al.

Battery energy storage systems (BESSs) need to comply with grid code and fault ride through (FRT) requirements during disturbances whether they are in charging or discharging mode. Previous literature has shown that constant charging current control of BESSs in charging mode can prevent BESSs from complying with emerging grid codes such as the German grid code under stringent unbalanced fault conditions. To address this challenge, this paper proposes a new FRT-activated dual control strategy that consists of switching from constant battery current control to constant DC-link voltage control through a positive droop structure. The results show that the strategy ensures proper DC-link voltage and current management as well as adequate control of the positive- and negative-sequence active and reactive currents according to the grid code priority. It is also shown that the proposed FRT control strategy is tolerant to initial operating conditions of BESS plant, grid code requirements, and fault severity.

Nourhan A. Maged, Hany M. Hasanien, Essamudin A. Ebrahim et al.

Abstract The present work develops a novel gorilla troops optimization algorithm (GTO) for optimal control of an autonomous microgrid. The proposed proportional‐integral controller parameters are properly designed by the GTO algorithm. It is based on the integral squared error to minimize the system objective function. The suggested islanded microgrid system operates with several decentralized, electronically interfaced energy resources and their local loads. The new optimal controller is applied to regulate its voltage at the different points of common coupling and its frequency despite the load variation. The performance of the new proposal is compared with the PI controller that was designed by a particle swarm optimization algorithm. It is observed that the microgrid functioning operation is improved even more by applying a GTO‐based than the other. The control strategy is thoroughly tested using a Matlab/Simulink simpower‐system environment under various microgrid operating situations. It is also implemented with OPAL 4510 real‐time hardware in the loop and a rapid control prototyping module. The different benchmark experiments serve to show the superiority of the new optimizer.

Zhike Xia, Pei-Yong Feng, Xin Jing et al.

Reciprocating motion is a widely existing form of mechanical motion in the natural environment. Triboelectric nanogenerators (TENGs) that work in sliding mode are ideal for harnessing large-distance reciprocating motion, and their energy conversion efficiency could be greatly enhanced by adding springs to them. Herein, we focused on investigating the design and optimization principles of sliding mode TENGs by analyzing the effects of spring parameters and vibration frequency on the triboelectric output performance of typical cylindrical sliding TENGs (CS-TENGs). Experimental study and finite elemental analysis were carried out based on a CS-TENG model assembled using a polytetrafluoroethylene (PTFE) film as the negative layer and an aluminum film as the positive layer. The energy output was found to be mainly affected by the change of relative displacement between the two friction layers, rather than the reactive force applied by the springs or the velocity of the sliding motion. However, the frequency of the output signals could be improved when the stiffness coefficient of the springs and the CS-TENG vibration frequency were increased. This study provides valuable directions for the design and optimization of sliding mode TENGs containing springs, and will motivate in-depth research on the fundamental principles of TENG operation.

Abu Saleh Ahmed, Nur Adibah Abdul Rahim, Md Rezaur Rahman et al.

Fossil fuels are widely recognized as non-renewable energy resources. They play an important role in our daily life because they can be used in various applications such as the production of soap and cosmetics, as an energy source and for transportation. However, the use of these fossil fuels causes negative impacts on humans, animals and the environment. These happen due to the emission of harmful gases into the atmosphere. Not only that, the available fossil fuels are decreasing due to continuous usage by humans. As a result, researchers investigated finding alternative ways to overcome this issue by replacing diesel fuel with biodiesel. Biodiesel is more environmentally friendly relative to diesel fuel. A research study was conducted involving biodiesel. The purpose of this study was to produce Jatropha Biodiesel, as well as evaluate the properties of Jatropha biodiesel and diesel Jatropha biodiesel blended with propanol. The production of Jatropha Biodiesel was done by using two-step transesterification which was an acid-catalyzed transesterification and base-catalyzed transesterification. Different methanol to oil ratios had been used to identify the best ratio to reduce the FFA content in the CJO. 9:1 was the best methanol to oil ratio and then tested with different catalyst weights. It was found that an increase in the weight of catalyst might reduce the amount of biodiesel yield. In addition, this study also investigated and predicted the engine performance and characteristics of diesel Jatropha biodiesel blended with propanol at different blending ratios. The properties of these test fuels were studied. Bomb calorimeter, Fourier Transform Infrared Spectroscopy (FT-IR) analysis and Diesel Engine test were done. Thus, the calorific value and functional group of the test fuels were identified and determined. The calorific value of biodiesel was much higher than conventional diesel due to the existence of oxygen. This could be proven as the analysis of FT-IR also showed a (C=O) bond which reflected the presence of oxygen. The oxygen helped in combustion besides reducing the hydrocarbon released into the air. These findings were then reflected and related to the performance of diesel engines.

Hajime NAKAMURA

In surface temperature measurement by thermocouple, measurement error was quantitatively investigated when the temperature measuring junction was adhered to the surface and a part of the lead wire was placed on the isothermal surface. First, heat paths of a thermocouple were modeled by thermal-resistance-network. Unknown parameters related to the contact between the thermocouple and the surface were estimated based on the measured data. The error ratio calculated by the thermal-resistance-network model agreed well to the experimental data both quantitatively and qualitatively, which indicates the validity of this model. Then, an analytic solution was derived with only main heat paths of the thermal-resistance-network. As a result, it was confirmed that even with only main heat paths, a reasonable error-ratio corresponding to the measurement can be obtained. Using the analytic solution, the error-ratio was calculated against various parameters, such as type and diameter of metal wire, gap between the junction and the surface, thermal conductivity of adhesive, lead-length placed on the isothermal surface, and so forth. Based on the analytic results, the effective method was presented to reduce the measurement error.

M. Fligiel, R. Patyk

The present study analyzes the operation length of internal forces (DDSW) understood as the length of the flow of internal forces along the shortest possible internal routes. The operation length of internal forces is determined on the basis of stresses and the given volume in the constructional space. The minimum DDSW of the structure satisfies the criterial conditions of the most rigid structure, where the potential energy of deformation and the deformation energy potential is the same in the whole volume and thus the potential gradient is zero.

Kai Zhang, W. Li, Jian Li et al.

You Zhangping

Hao Ruican

Christopher A. Lemmon, L. Romer