• Journal of Aerospace System Engineering
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• v.17 no.6
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• pp.149-153
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• 2023

In this study, structural design and analysis of a duct stand for blowers were performed. This structure was an axial fan and blower for wind tunnel of the vehicle environmental test chamber. The design of the blower duct stand support structure was performed by investigation on various loads. Additionally, self-weight of the motor and weight of the duct were investigated and applied. The duct stand structure was designed by analyzing the load. The safety of the structural design results was evaluated through finite element analysis. Finally, the safety of the design result was verified.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.8
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• pp.771-782
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• 2017

This paper describes the development of a wearable robot to assist ankle power for the elderly. Previously developed wearable robots have generally used motors and gears to assist muscle power during walking. However, the combination of motor and reduction gear is heavy and has limitations on the simultaneous control of stiffness and torque due to the friction of the gear reducer unlike human muscles. Therefore, in this study, Mckibben pneumatic muscle, which is lighter, safer, and more powerful than an electric motor with gear, was used to assist ankle joint. Antagonistic actuation using a pair of pneumatic muscles assisted the power of the soleus muscles and tibialis anterior muscles used for the pitching motion of the ankle joint, and the model parameters of the antagonistic actuator were experimentally derived using a muscle test platform. To recognize the wearer's walking intention, foot load and ankle torque were calculated by measuring the pressure and the center of pressure of the foot using force and linear displacement sensors, and the stiffness and the torque of the pneumatic muscle joint were then controlled by the calculated ankle torque and foot load. Finally, the performance of the developed ankle power assistive robot was experimentally verified by measuring EMG signals during walking experiments on a treadmill.

• The Journal of Korean Physical Therapy
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• v.22 no.4
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• pp.15-20
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• 2010

Purpose: The purpose of this study was to measure changes in the H-reflex and V wave under loading conditions (e.g. prone and standing position) and to investigate whether postural change would affect the H-reflex and V wave in post stroke hemiplegic patients. Methods: Thirty persons with hemiplegia resulting from stroke (20 males, 10 females) participated in this study. Electromyography (EMG) was used to electrically stimulate and record the soleus H-reflexes and V waves under various loading conditions. The normality of the distribution of each variable (H latency, $H_{max}/M_{max}$ ratio, $V_{max}/M_{max}$ ratio) was tested using the Kolmogorov-Smirnov test. The means of normally distributed continuous data were assessed by independent t-test (${\alpha}$=0.05). Results: There were statistically significant differences in $H_{max}/M_{max}$ ratio (p<0.01), $V_{max}/M_{max}$ ratio (p<0.01), H latency (p<0.01) among the prone and standing position. Conclusion: We found that the H-reflex and V wave in standing position was more active to weight bearing load than prone position.

• Bulletin of the Korean Chemical Society
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• v.35 no.12
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• pp.3475-3481
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• 2014

This paper describes how primary contaminants in ambient air affect the performance of the cathode in fuel cell electric vehicle applications. The effect of four atmospheric pollutants ($SO_2$, $NH_3$, $NO_2$, and CO) on cathode performance was investigated by air impurity injection and recovery test under load. Electrochemical analysis via polarization and electrochemical impedance spectroscopy was performed for various concentrations of contaminants during the impurity test in order to determine the origins of performance decay. The variation in cell voltage derived empirically in this study and data reported in the literature were normalized and juxtaposed to elucidate the relationship between impurity concentration and performance. Mechanisms of cathode degradation by air impurities were discussed in light of the findings.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.5
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• pp.529-536
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• 2019

In this paper, the signals of the sensor for extracting characteristic parameters of the rotor are collected and the performance of the extraction technique is analyzed. To this end, a vibration test league was developed for conducting model tests to analyze the signal characteristics under normal operation. As a result, it is judged that no change in the measured the raw data amplitude will occur in the acceleration sensor with the unbalanced mass measured from the acceleration sensor. Performing FFT showed a significant increase in amplitude of the rotational frequency of 20 Hz as the unbalanced mass increased. The analysis results according to the change in the unequal mass of the speed sensor also showed a significant increase in the 1X Harmonics component, such as the acceleration sensor. There was no change in the amplitude of the acceleration sensor data when the misalignment occurred, and for the Envelope data, the amplitude of 2X (40 Hz) was increased depending on the degree of misalignment. The velocity sensor at change of misalignment also showed similar results to the acceleration sensor, and the peak was reduced at 600 Hz as the load increased in the frequency spectrum.

• Journal of The Korean Society of Integrative Medicine
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• v.10 no.1
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• pp.129-136
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• 2022

Purpose : The purpose of this study was to investigate the effect of applying intensity on the muscle activity and muscle hardness of the upper trapezius muscle in adult males when TENS (transcutaneous electrical nerve stimulation) was applied. In addition, this study intends to prepare the scientific basic data of TENS for the purpose of relaxation based on the experimental results. Methods : Eighty-seven healthy adult males participated in the experiment, and they were randomly divided into an experimental group and a control group. All subjects in this study were healthy subjects without musculoskeletal or nervous system damage. All subjects were subjects who voluntarily consented to the purpose and method of the experiment. All subjects were provided with a load by typing for 20 minutes, and muscle activity and muscle hardness of the upper trapezius muscle were measured immediately. Afterwards, TENS was given to each groups for 15 minutes, and the experimental group received stimulation at the motor threshold level, and the control group received a placebo stimulation. After stimulation, muscle activity and muscle hardness of the upper trapezius muscle were measured in the same method. The measured data were compared between groups through an independent t-test and dependent t-test. The statistical significance level was set at .05. Results : The application of TENS statistically significantly decreased the muscle activity and muscle hardness of the trapezius muscle in the experimental group, and the results showed a significant difference from the control group. Conclusion : Application of TENS significantly decreased the muscle activity and muscle stiffness of the upper trapezius muscle. The application of TENS of applying intensity that induces muscle contraction may induce relaxation by reducing the muscle activity and muscle hardness of the trapezius muscle.

• The Journal of the Korea Contents Association
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• v.9 no.12
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• pp.391-399
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• 2009

The purposes of the present investigation was to evaluate the effects of loaded and unloaded swimming stimulation after central nerve system injury in the rats. SCI model rats were damaged in L1-L2 injected with 6-OHDA. The twenty one Sprague-Dawley adult male rats weights($200\pm10g$) were randomly divided into control group and 2 swimming groups and then swimming groups divided into 15 minute unloaded swimming group and 15 minute loaded swimming group by swimming intensity. Behavioral Change was evaluated by the BBB(Basso, Brestti, Brenahan) scales test and the maximal angles of the inclined board on which the rat could maintain its intial position for the progressive locomotor recovery. Using enzyme-linked immunosolbent assays(ELISA), we measured concentrations of brain-delived growth factor(BDNF) in serum after swimming. There was significant change of BBB scores in control group as compared to unloaded swimming group and loaded swimming group(p<.05), and unloaded swimming group were significantly higher than loaded swimming group(p<.05). The maximal angles of the inclined plane test were higher in the unloaded swimming group and loaded swimming group than the control group(p<.05), and loaded swimming group were significantly lower than unloaded swimming group(p<.05). There were singnificant difference of concentration of BDNF in serum change in each group(p<.05). The results suggest that swimming applied from the early phase after spinal cord injury may be beneficial in the early recovery of motor function.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.5
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• pp.471-478
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• 2010

Thin films play an important role in many technological applications including microelectronic devices, magnetic storage media, MEMS and surface coatings. It is well known that a thin film's material properties can be very different from the corresponding bulk properties and thus there has been a strong need for the development of a reliable test method to measure the mechanical properties of a thin film. We have developed an alternative and convenient test method to overcome the limitations of previous membrane deflection experiment and uniaxial tensile test by adopting a white light interferometer having sub-nanometer out-of-plane displacement resolution. The freestanding aluminium specimens are tested to verity the effectiveness of the test method developed and get the tensile properties. The specimens are 0.5 rum wide, $1{\mu}m$ thick and fabricated through MEMS processes including sputtering. 1 to 5 specimens are fabricated on Si dies. The membrane deflection experiments are carried out by using a homemade tester consisted of a motor-driven loading tip, a load cell, and 6 DOF alignment stages. The test system is compact enough to set it up beneath a commercial white light interferometric microscope. The white light fringes are utilized to align a specimen with the tester. The Young's modulus and yield point stress of the aluminium film are 62 GPa and 247 MPa, respectively.

• Journal of Advanced Marine Engineering and Technology
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• v.15 no.4
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• pp.29-45
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• 1991

Lip type stern tube sealing systems have used in almost all the middle or large ships which are being constructed in these days. It seems that the pressure fluctuation of the seal ring interspace, the cross-section profile and the materials quality of the seal rings have great effects on the sealing fuction of this sealing system. In this paper, the mechanical movement of lip seal ring which plays the most important role in stern tube sealing system and the possibility of leakage caused by pressure fluctuation are studied by theory and experiment. Using the finite element method for the axi-symetric object which receives the torsional load, the displacement and stress analysis of the seal rings, and also the possibility of crack occurance is checked by theoretical analysis. If the force which seal ring lip periphery receives is too small, there will be the possibility of leakage caused by the pressure fluctuation of the seal ring interspace, and if this force is too large, the frictional force between the seal ring and the liner will become problematical. The possibility of leakage caused by hardening of seal ring materials and creep phenomena of tested seal rings are also examined. The trial seal rings were designed and manufactured using the program of displacement and stress analysis developed in this study and the experimental apparatus to test the trial seal rings was also designed and manufactured. This trial seal rings were fitted in the experimental apparatus which was made in the same form as an actual stern tube. The one side of this apparatus was filled with sea water and the other side of it was filled with the lubricating oil. The leakage of oil and sea water was checked and the temperature was measured, rotating the propeller shaft at the constant velocity by D.C. motor. It was proved that the trial seal rings made in Viton rubber functioned excellenty but the trial seal rings made in N.B.R. rubber had problem in its durability.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.4
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• pp.328-341
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• 2017

In the control actuator system of a launch vehicle based on thrust vectoring, the interaction between electro-mechanical position servo and inertial load are combined with the dynamic characteristics of the flexible vehicle support to generate synthetic resonance. This occurred resonance is fed back to the attitude control system and can influence stability of launch vehicle. In this study, we proposed a simulation model to analyze synthetic resonance of electro-mechanical actuation system for thrust vector control and explained the results of simulation and test using dynamic force feedback control which improves dynamic characteristics of servo actuation system by reducing synthetic resonance.