Research Paper
Dynamic Response
J. Akbari; S. Mirzaei
Abstract
Numerical techniques for solving dynamic structural problems often encounter significant challenges, including conditional stability, period elongation errors, amplitude decay errors, and the emergence of spurious frequencies. To address these issues, several first-order precise integration methods have ...
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Numerical techniques for solving dynamic structural problems often encounter significant challenges, including conditional stability, period elongation errors, amplitude decay errors, and the emergence of spurious frequencies. To address these issues, several first-order precise integration methods have been developed; however, these approaches still suffer from errors associated with the inversion of the state matrix. This study employs the singular value decomposition technique to enhance the efficiency of the precise integration method algorithm and eliminate the singularity of the state matrix. The robustness of the proposed method is evaluated across various transient dynamic problems. The results demonstrate that traditional approaches, such as the Newmark method, exhibit substantially larger errors—exceeding 150% in certain cases. Ultimately, the findings emphasize that accurately estimating the dynamic response of multi-degree-of-freedom systems under impact loading requires careful consideration. Conventional methods, including the Newmark average acceleration technique, should therefore not be applied indiscriminately.
Research Paper
Robotics
B. Sarikhani; M. A. Ahmadi-Pajouh; A. Kolivand; F. Bakhtiari-Nejad
Abstract
The hand plays a crucial role in daily activities; injury or paralysis significantly reduces independence. Therefore, robotic hand exoskeletons have been developed to restore motor function safely and effectively. Considering the major role of the hand in daily activities, many researchers have been ...
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The hand plays a crucial role in daily activities; injury or paralysis significantly reduces independence. Therefore, robotic hand exoskeletons have been developed to restore motor function safely and effectively. Considering the major role of the hand in daily activities, many researchers have been working on hand rehabilitation exoskeletons. This research presents the design and implementation of a tendon-driven exoskeleton for finger rehabilitation. Continuous passive motion devices are used to maintain and restore the range of motion of the joints. The exoskeleton has been designed to help patients easily perform functional tasks. To achieve this goal, an adjustable thimble mechanism with flexible filament and a finger guide was designed. Also, this design provides the necessary force to fully guide the fingers through the whole range of motion of the joints. The designed mechanism has been modeled and simulated in MATLAB software. It has also been tested on healthy human subjects. Recorded images from the index finger in a complete range of motion have been analyzed to find the finger trajectory during flexion. The metacarpophalangeal joint of the index finger in healthy subjects has a range of motion between 0 and 90 degrees, while the exoskeleton can provide a range of motion between 0 and 94 degrees. Results show that the designed exoskeleton can provide sufficient force and an acceptable range of motion for patients up to level 2 of the Ashworth scale, which is acceptable for most different and functional varieties of continuous passive motion exoskeletons.
Research Paper
Hydraulic and Pneumatic Systems
Tohid Jamali Rovesht; Mohammad Manafpour
Abstract
The occurrence of the cavitation phenomenon in hydraulic structures operating under high flow velocities remains a critical challenge. Efficient mitigation strategies may include increasing air concentration and optimizing the geometric design, such as minimizing sharp changes in flow direction and reducing ...
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The occurrence of the cavitation phenomenon in hydraulic structures operating under high flow velocities remains a critical challenge. Efficient mitigation strategies may include increasing air concentration and optimizing the geometric design, such as minimizing sharp changes in flow direction and reducing local vortices. The Seymareh dam bottom outlet, operating under high water heads, is prone to cavitation due to its velocity and pressure fields. This study numerically investigates the effects of geometric modifications on cavitation risk reduction. Results showed that removing lateral expansion increases cavitation indices on outlet walls, while designing a concave curved bed elevates pressure and cavitation indices on the bed surface. Nonetheless, implementing both modifications together completely suppresses cavitation risk. The numerical analysis was conducted under single-phase flow conditions, without considering air entrainment, which, in practice, could further improve outlet safety. These findings could provide useful insights for geometric design approaches to control cavitation in high-velocity hydraulic structures.
Research Paper
Machining
A. Mehrvar; AR. Mirak; M. Motamedi
Abstract
Electrochemical machining (ECM) is an effective method for machining CMSX-4 superalloy, a single-crystal nickel-based superalloy, due to its unique performance in metal machining. The microstructure of this superalloy consists of three phases: gamma (γ), gamma prime (γ'), and carbide. The ...
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Electrochemical machining (ECM) is an effective method for machining CMSX-4 superalloy, a single-crystal nickel-based superalloy, due to its unique performance in metal machining. The microstructure of this superalloy consists of three phases: gamma (γ), gamma prime (γ'), and carbide. The gamma prime phase is distributed cubically and homogeneously in the gamma field without any boundaries. It is essential to maintain this microstructure after the production process. In the present study, ECM was performed on a CMSX-4 superalloy workpiece. The microstructure of the workpiece was then investigated before and after ECM using scanning electron microscopy and energy-dispersive spectroscopy analysis from two sides. The results showed that no changes were observed in the CMSX-4 microstructure after ECM process. The single-crystal structure and the distribution of the gamma prime phase were maintained after this machining process, indicating that ECM is an effective machining method for CMSX-4 superalloy without compromising its critical microstructural features.
Research Paper
Optimization
A. Haitao Zhang; B. Li Guan; C. Long Chang
Abstract
Rolling bearings are critical components of rotating machinery, and their health status directly affects the operational reliability of equipment. This paper proposes an optimized wavelet-SVM fault diagnosis method based on multi-source vibration signal fusion: Three-channel inputs are constructed by ...
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Rolling bearings are critical components of rotating machinery, and their health status directly affects the operational reliability of equipment. This paper proposes an optimized wavelet-SVM fault diagnosis method based on multi-source vibration signal fusion: Three-channel inputs are constructed by synchronously collecting vibration signals from the drive end and fan end, along with their differential signals; Wavelet packet decomposition is utilized to extract frequency-domain features such as unit node energy entropy and wavelet coefficient standard deviation, while dimensionless indicators independent of rotational speed (kurtosis factor/waveform factor/impulse factor) are introduced to enhance time-domain characterization; The fused features are input into an RBF-SVM classifier after dimensionality reduction via PCA (retaining 99% variance, reducing dimensions from 102 to 4). Experiments indicate that on the CWRU dataset, this method achieves 97.0% precision, 96.9% recall, and an F1-score of 96.9% (representing a 2.9% improvement over single-source input methods); Although there is a 2.4% absolute accuracy gap compared to deep learning solutions, it possesses significant edge advantages—memory usage is only 12KB and inference latency is 0.6ms—providing a high-precision, low-cost embedded solution for rotating machinery fault diagnosis
Research Paper
Micro and Nano Systems
A. A. Naseri; N. Naserifar
Abstract
Cancer is a common and often devastating disease affecting many individuals. This condition is frequently perceived as incurable; however, scientific advancements have shown that most cancers are treatable if detected early. The first step in diagnosing cancer is often identifying circulating tumor cells ...
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Cancer is a common and often devastating disease affecting many individuals. This condition is frequently perceived as incurable; however, scientific advancements have shown that most cancers are treatable if detected early. The first step in diagnosing cancer is often identifying circulating tumor cells in the bloodstream. Separator devices are employed for the identification of cancer cells. Currently utilized devices are often bulky and marker-based and may come with a biohazard exposure risk. The advancement of micro elector mechanical systems (MEMS) has given rise to smaller devices capable of markerless separation; however, these devices have not yet attained the performance level of conventional devices. Designing a device that can reliably isolate these rare cells is a challenging task. Designing a device that can reliably isolate cancer cells with a high degree of confidence is crucial. In this study, we present a method for model preparation capable of simulating multiple physics. Subsequently, we introduce an optimization process for mesh size. We aim to investigate the design parameters for a novel cell separation device based on buoyancy and a chevron channel. This device has the potential to increase the purity of separators by 10% increase overall acoustic pressure and decrease shear drag. Chevron channel flow pattern if properly aligned can contribute to cell separation of acoustic radiation force or counteract it if necessary. Utilizing buoyancy force for cell separation based on cell density is a prominent feature of acoustic-chevron separator devices. Finally, chevron channel capabilities and design constraints are discussed.
Research Paper
Computational Fluid Dynamics (CFD)
I W. Y. Arta; A. Ghurri; I K. Warjaya
Abstract
The cooling system used in brushless direct current motors employs an air-cooling mechanism with fins on the motor heatsink. The optimal performance of brushless direct current motor cooling is not yet fully understood, necessitating an analysis of the cooling process. This study employs two methods, ...
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The cooling system used in brushless direct current motors employs an air-cooling mechanism with fins on the motor heatsink. The optimal performance of brushless direct current motor cooling is not yet fully understood, necessitating an analysis of the cooling process. This study employs two methods, experimental and simulation, to investigate cooling efficiency. The results indicate that the temperatures of the winding and heatsink increase with the electric motor's rotation speed. The highest temperature recorded with a thermocouple was 94℃ at 2000rpm. Validation of the simulation results against the experimental results showed a 2% deviation, indicating their validity. Based on these findings, three new heatsink designs, namely modif 1, modif 2, and modif 3, were developed. Simulation results revealed that modif 3, a combination of axial and radial heatsink shapes, exhibited the most effective temperature transfer. Therefore, it can be inferred that higher motor rotation speeds can lead to increased motor heat. The study concludes that a combination heatsink design is capable of reducing temperatures in brushless direct current motors, as demonstrated through CFD simulations on electric motor prototypes.
Research Paper
Machining
Mohammad Reza Shabgard; Reza Rostami Heshmatabad
Abstract
In this study, relationship between effect of machining parameters on machining characteristics and surface morphology was studied in electrochemical machining (ECM). The characteristics were Material Removal Rates (MRR), Over Cut (OC), Surface Roughness (SR) and surface morphology. The results show ...
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In this study, relationship between effect of machining parameters on machining characteristics and surface morphology was studied in electrochemical machining (ECM). The characteristics were Material Removal Rates (MRR), Over Cut (OC), Surface Roughness (SR) and surface morphology. The results show that MRR is increased by increasing current but OC is decreased. Increasing concentration causes to increase MRR, OC and SR. Also, the analysis of surface morphology shows that the electrolyte type affects the dissolution mechanism and surface layer formation in ECM. There are cavities in NaCl and KCl that their diameter, depth and distribution on the machined surface are changed by parameters and their diameters were 4μm to 9μm. Increasing ion concentration causes to enhance the diameter size and depth of created cavities on work piece but their uniform distribution decreases, while the current has a reverse effect on them. On the other hand, an oxide layer is formed on the machined surface in NaNO3 and by increasing current and concentration, breaking and the anion cavity effect are increased on this layer. So, increasing the MRR and SR is due to this phenomenon in NaNO3.
Research Paper
Damage Mechanics
V. Samadi; M. Mostafaei; A. N. Lorestani
Abstract
This study presents a non-invasive method for detecting mechanical faults in a single-phase AC electromotor using processed acoustic signals. Sound data were collected via a USB-connected microphone installed in the motor's electrical casing under diverse operating conditions. Ten statistical features ...
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This study presents a non-invasive method for detecting mechanical faults in a single-phase AC electromotor using processed acoustic signals. Sound data were collected via a USB-connected microphone installed in the motor's electrical casing under diverse operating conditions. Ten statistical features were extracted from the acoustic signals and used as input to three classification algorithms: Linear Discriminant Analysis (LDA), Quadratic Discriminant Analysis (QDA), and Support Vector Machine (SVM). Model performance was evaluated using confusion matrix metrics, including specificity, accuracy, precision, and sensitivity. Among the classifiers, SVM outperformed others, achieving average values of 99.54, 99.16, 97.15, and 96.17, respectively, with 10-fold cross-validation confirming its superior consistency (99.88% specificity, 99.17% accuracy). The findings confirm that acoustic signal analysis is a reliable and cost-effective tool for real-time fault diagnosis in electromotors. Defects may be accurately found in the electromotor by using acoustic analysis to monitor its status. The proposed framework is adaptable to other rotating machinery through retraining, offering a valuable solution for predictive maintenance in industrial applications.
Research Paper
Fuel Cells
Mehdi Borji
Abstract
A comprehensive investigation has been conducted into the direct internal reforming planar type solid oxide fuel cell (DIR-PSOFC) through numerical analysis. The mathematical modeling of DIR-PSOFC is achieved through the implementation of conservation equations and a comprehensive electrochemical model. ...
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A comprehensive investigation has been conducted into the direct internal reforming planar type solid oxide fuel cell (DIR-PSOFC) through numerical analysis. The mathematical modeling of DIR-PSOFC is achieved through the implementation of conservation equations and a comprehensive electrochemical model. The synthesis gas fuel is introduced into the fuel channel, where both carbon monoxide (CO) and hydrogen (H2) undergo electrochemical oxidation. Gas flows are treated as plug flows with a co-flow configuration. Results of the simulation are then compared with and without the inclusion of carbon monoxide electrochemical oxidation. This comparison encompasses temperature fluctuations along the cell's longitudinal axis and the mole fraction variations of all gaseous species along the cel length, in addition to the electrical performance of the SOFC. It has been demonstrated that CO accounts for only 20% of the total current density. The contribution of CO to the generation of electric current at the inlet is 15%. At the point of maximum current density, the value is 16.17%. The cell operating voltage, power density, and fuel efficiency have been demonstrated to exhibit an enhancement, with an augmentation observed from 0.68 to 0.75 V, 3411.396 to 3739.130 W/m2, and 45.83% to 50.23%, respectively, when CO is used as a reactant in the anode side TPB. It has been determined that the electrochemical reaction of CO results in elevated heat generation within the cell, which in turn enhances the operating temperature. Consequently, the activation and ohmic losses are diminished, thereby improving the local current density and cell operating voltage.
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