A lamb wave propagation behavior on a freestanding nanoscale membrane was investigated using a laser ultrasonic technique in the present study. A 110-nm thick aluminum (Al) layer was deposited on a rectangular 200-nm thick silicon nitride (SiN) membrane and the Lamb wave was launched using a pulsed laser. The transfer matrix technique was employed to obtain a theoretical dispersion curve so that material properties of the SiN membrane could be estimated through curve-fitting. In addition, picosecond ultrasonic measurement was used to characterize the Al film. Results showed that the dispersive behavior of Lamb wave in the fundamental antisymmetric mode could be clearly observed on the membrane. However, comparison of dispersion curves indicated that the effect of residual stress of the film became more influential at a low dimensional scale.
In this study, the Inertial Measurement Unit (IMU) signals and clinical evaluation scales for Parkinson"s disease were correlated. The study included 16 patients diagnosed with Parkinson"s disease. Each subject was evaluated based on Korean Mini-Mental State Examination (KMMSE), Unified Parkinson"s Disease Rating Scale (UPDRS) part 3, New Freezing of Gait Questionnaire (NFOGQ) parts 2 & 3, and Hoehn & Yahr Scale (H&Y). All subjects performed the Time Up and Go test by attaching IMU sensors to both ankles and torso. Based on the tilting angle of torso and the time of first step, the freezing and non-freezing windows were determined. Seven IMU features involving the ankle signals were calculated in the specific window. Spearman’s correlation analysis of clinical evaluation scales was performed. As a result, the freezing index and power of locomotion band (0.3-3 Hz) were recommended to determine UPDRS part 3. Also, the intensity of the locomotion band facilitated evaluation of NFOGQ part 3 regardless of freezing of gait.
Shape memory alloy (SMA) has been widely used for many engineering and scientific applications, because it is largely deformable with high power density, and can be actuated easily by resistive heating. It is possible to reduce the size of the actuators by integrating or embedding SMA into the structures. While many applications have been reported regarding linear or bending actuators using the SMA wire, the development of a rotary actuator remains important and challenging for the engineering applications. Here, a new type of millimeter-scale rotary actuator is proposed based on the twisted SMA wires. SMA wires are twisted, folded, and integrated into the rotary actuator, and simple change of the twist direction enables the rotary actuator to rotate in the opposite direction. By integrating the oppositely twisted SMA wires into one rotary actuator unit, bidirectional rotary motions are possible. The actuation mechanism, design, and fabrication processes of the proposed rotary actuator are presented and demonstrated with its actuation performance. The fabricated actuators had average rotary working ranges from -38.68±4.92 deg to +45.37±8.79 deg in counterclockwise (CCW) and clockwise (CW) directions. This study will leverage the practical advances in the relevant engineering and scientific applications.
Citations
Citations to this article as recorded by
A Novel Force-Couple SMA Rotary Actuator for MEMS Safety and Arming Device Yun Cao, Zeyi Chai, Yikang Huang, Mo Yang, Hengbo Zhu, Weirong Nie, Zhanwen Xi IEEE Sensors Journal.2025; 25(19): 35879. CrossRef
Multi-field coupled dynamics for a movable tooth drive system integrated with shape memory alloys Lizhong Xu, Zhenglong Fu Heliyon.2023; 9(7): e17531. CrossRef
Design, Fabrication, and Control of a Rotary Manipulator driven by Twisted Shape Memory Alloy (SMA) Wires Gil-Yong Lee, Su-Yeon Lee Journal of the Korean Society for Precision Engineering.2023; 40(8): 665. CrossRef
Largely deformable torsional soft morphing actuator created by twisted shape memory alloy wire and its application to a soft morphing wing Su-Yeon Lee, Gil-Yong Lee Scientific Reports.2023;[Epub] CrossRef
Nature-inspired architected materials have been widely used to achieve efficient structural materials by harnessing their cellular and hierarchical structures. For example, biological materials observed in bone, shell, nacre, and wood contain constituents, ranging from nanometers to centimeters, arranged in an ordered hierarchy. Because of their composited structures that contain micro and nanoscale building blocks arranged in an ordered hierarchy and the material size effect in the mechanical strength of nano-sized solids, bioceramic materials are mechanically robust and lightweight. The design principles offered by hard biological materials of multiscale composite structures can assist in the creation of advanced ceramic architectures. In addition, the evolution of additive manufacturing technologies has enabled the fabrication of materials with intricate cellular architected materials. In this review, we discussed advanced additive manufacturing for the fabrication of nature-inspired multiscale ceramic structures by combining conformal thin-film coating technique with conventional additive manufacturing methods.
Citations
Citations to this article as recorded by
SEM Image Quality Improvement and MTF Measurement Technique for Image Quality Evaluation Using Convolutional Neural Network Chan Ki Kim, Eung Chang Lee, Joong Bae Kim, Jinsung Rho Journal of the Korean Society for Precision Engineering.2023; 40(4): 275. CrossRef
In this study, both mechanical power and the wind speed distribution in the wake of a wind turbine scaled model were analyzed using a commercial CFD program (Ansys CFX) along with experimental validation. For the simulation, two different turbulence models including the SST model and the k-ε model were used. The scaled model was originally designed and manufactured by the researchers at the Technical University of Munich and was slightly modified for this research. To experimentally verify the CFD results, tests were performed with the scaled model under the turbulent wind in a wind tunnel. From the experimental validation, it was found that the k-ε turbulence model gives a better prediction than the SST model in the wake results. However, the SST turbulence model showed better prediction than the k-ε turbulence model in the power prediction. The discrepancy between the CFD results and the experimental validation is partially due to the fact that the blades are deformed at all times and control of pitch in the rated power region but these aspects are not considered in the simulation. If a transient analysis is performed using LES models, it will more accurately predict the change of wake with high turbulence intensity.
Citations
Citations to this article as recorded by
Design and Performance Analysis for 3 MW Waste Pressure Steam Turbine Using 2D and 3D Numerical Simulation Hwabhin Kwon, Jong Yun Jung, Joon Seob Kim, Ye Lim Jung, Heesung Park Journal of the Korean Society for Precision Engineering.2021; 38(6): 455. CrossRef
This paper deals with the development of a passive modular hip exoskeleton system aimed at preventing musculoskeletal low back pain, which commonly occurs in heavy weight transport workers, by improving back muscle strength. The passive exoskeleton system has the advantage of being lightweight, making it suitable for modular exoskeleton systems. The cam and spring actuator designed in this study was applied to the passive modular exoskeleton system to build human hip and lumbar muscle strength. In order to evaluate the effectiveness of the passive modular exoskeleton system, a test was performed in which a subject lifted a 15 kg weight three times in a stoop posture, using heart rate measurement and Borg scale recording. According to the results, all subjects showed 26.83% lower maximum heart rate and 34.73% lower average heart rate than those who did not wear the system, and Borg scale evaluation result was lower. All subjects wore this system and did not experience back pain during the experiment. Through this study, we validated the effectiveness of the passive modular exoskeleton system and proved that this system can build the strength of industrial workers and be a solution to prevent musculoskeletal lumbar disease.
In this study, blades manufactured by 3D printing technology were experimentally tested to be used for a scaled wind turbine in a wind tunnel. The scaled model was originally designed and manufactured by researchers at the Technical University of Munich. The model has been slightly modified to adopt the 3D printed blades for this study. Also, control algorithms for the power maximization in the low wind speed regions were constructed and applied to a commercial programmable logic controller for wind tunnel tests of the scaled model. For comparison, the scaled model was also modeled in MATLAB/Simulink and dynamic simulations were performed with the measured wind speed as an input. The simulation results seemed to overpredict the experimental results initially, but by considering the unexpected extra generator torque due to friction of the shaft, the errors were reduced to be less than 5%. Based on this study, the application of 3D printed blades to the wind turbine scaled models of a similar rotor diameter was found to be an efficient and effective way of blade manufacturing and scaled model testing.
Citations
Citations to this article as recorded by
Performance Validation of Control Algorithm Considering Independent Generator Torque Control in PCS Dongmyoung Kim, Min-Woo Ham, Insu Paek, Wirachai Roynarin, Amphol Aphathanakorn Applied Sciences.2024; 14(24): 11598. CrossRef
The Suitability of Substructures of the Offshore Wind Power Complex Dae Kyung Kim, Dong Soon Kang, Jong Hak Lim, Young Il Byun, Chul Ki Song Journal of the Korean Society for Precision Engineering.2022; 39(4): 299. CrossRef
CFD Analysis of the Mechanical Power and the Wake of a Scaled Wind Turbine and Its Experimental Validation Yechan Hwang, Insu Paek Journal of the Korean Society for Precision Engineering.2021; 38(3): 223. CrossRef
Design and Validation of Demanded Power Point Tracking Control Algorithm for MIMO Controllers in Wind Turbines Taesu Jeon, Dongmyoung Kim, Yuan Song, Insu Paek Energies.2021; 14(18): 5818. CrossRef
To study the geometrical scale dependency of thin film solid oxide fuel cells (SOFCs), we fabricated three thin films SOFCs with the same cross-sectional structure but with different electrode areas of 1, 4 and 9 ㎟. Since the activation and ohmic losses of SOFCs depend on their active region, we examined the variations of the power density of the cells with a Pt (anode)/sputtered YSZ/Pt (cathode) structure. We found that a cathode electrode with a low aspect ratio may suffer from high ohmic and activation losses because of the geometrical scale dependency.
First
Prev
