• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.10
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• pp.19-26
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• 2021

In fine-particle injection processing, hard fine particles, such as silicon carbide or aluminum oxide, are injected - using high-pressure air, and a small amount of material is removed by applying an impact to the workpiece by spraying at high speeds. In this study, a two-axis stage device capable of sequence control was developed to spray various shapes, such as circles and squares, on the surface during the micro-particle jetting process to understand the surface-shape micro-particle-processing characteristics. In the experimental device, two stepper motors were used for the linear movement of the two degree-of-freedom mechanism. The signal output from the microcontroller is - converted into a signal with a current sufficient to drive the stepper motor. The stepper motor rotates precisely in synchronization with the pulse-signal input from the outside, eliminating the need for a separate rotation-angle sensor. The major factors of the processing conditions are fine particles (silicon carbide, aluminum oxide), injection pressure, nozzle diameter, feed rate, and number of injection cycles. They were identified using the ANOVA technique on the design of the experimental method. Based on this, the surface roughness of the spraying surface, surface depth of the spraying surface, and radius of the corner of the spraying surface were measured, and depending on the characteristics, the required spraying conditions were studied.

• Korean Journal of Optics and Photonics
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• v.30 no.6
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• pp.243-248
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• 2019

The respiratory tract is an essential part of the respiratory system involved in the process of respiration. However, if stenosis occurs, it interferes with breathing and can even lead to death. Asthma is a typical example of a reversible cause of airway narrowing, and the number of patients suffering from acute exacerbation is steadily increasing. Therefore, it is important to detect airway narrowing early and prevent the patient's condition from worsening. Optical coherence tomography (OCT), which has high resolution, is suitable for observing the microstructure of tissues. In this study we developed an endoscopic OCT system. We combined a 1300-nm OCT system with a servo motor, which can rotate at a high speed. A catheter was pulled back using a linear stage while imaging with 360° rotation by the motor. The motor was selected considering various requirements, such as torque, rotational speed, and gear ratio of pulleys. An ex vivo rabbit tracheal model was used as a sample, and the sample and catheter were immobilized by acrylic structures. The OCT images provided information about the structures of the mucosa and submucosa. The difference between normal and stenosed parts in the trachea was confirmed by OCT. Furthermore, through a three-dimensional (3-D) reconstruction process, it was possible to identify and diagnose the stenosis in the 3-D image of the airway, as well as the cross-sectional image. This study would be useful not only for diagnosing airway stenosis, but also for realizing 3-D imaging.

• Journal of Aerospace System Engineering
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• v.12 no.4
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• pp.75-80
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• 2018

The working principle of a satellite camera involves a focusing mechanism for controlling the focus of the optical system, which is essential for proper functioning. However, research on focusing mechanisms of satellite optical systems in Korea is in the beginning stage and developed technology is limited to a thermal control type. Therefore, in this paper, we propose a motor-driven focusing mechanism applicable to small satellite optical systems. The proposed mechanism is designed to generate z-axis displacement in the secondary mirror by a motor. In addition, three flexure hinges have been installed on the supporter for application of preload on the mechanism resulting in minimization of the alignment error arising due to manufacturing tolerance and assembly tolerance within the mechanism. After fabrication of the mechanism, the alignment errors (de-space, de-center, and tilt) were measured with LVDT sensors and laser displacement meters. Conclusively, the proposed focusing mechanism could achieve proper alignment degree, which can be applicable to small satellite optical system.

• Applied Microscopy
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• v.22 no.2
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• pp.30-45
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• 1992

An experimental study on the acute irradiation effects on the substantia nigra of head-irradiated rats were carried out. Rats anesthetized with sodium thiopental, were exposed only on their head areas with a single dose of 3,000 rads or 6,000 rads, respectively. Radiation was produced by Mitsubishi linear accelerator at the speed of 200 rads/min. Aminals were sacrificed on 6 hours, 2 days and 6 days following irradiations. By the perfusion fixation through the heart, rats were fixed with 1% glutaraldehyde-1% paraformaldehyde solution. Two hours later, brains were exposed and immersed in the same fixatives over night. Tissue blocks from subtantia nigra were punched out, and they were refixed in the 2% osmium tetroxide solution. Blocks were dehydrated through alcohol series, and embedded in the araldite mixture. Ultrathin sections were stained with uranyl acetate and lead citrate solutions, From the ultrastructural study, following results were made: 1. Six hours after irradiation, severe depletion of synaptic vesicles was occurred in the many axon terminals of the nigral neuropil. 2. Dramatical decrease of lysosomes and dense granules was observed. 3. Two days following irradiation, alterations of ribosomes, granular endoplasmic reticula, mitochondria, etc, were noticed. 4. Many of the malformations were seen to be repaired on the 6th day. 5. Above results were interpreted as follows. At the acute stage of heavy irradiation, neurotransmitters in the substantia nigra are released severely. But they are recovered within 6 days. It is concluded that acute head-irradiation may result severe disturbance of nigral motor control function during the first few days.

• Smart Structures and Systems
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• v.24 no.3
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• pp.303-317
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• 2019

Magneto-rheological fluid (MRF) rotatory dampers are normally used for controlling the constant rotation of machines and engines. In this research, such a device is proposed to act as variable stiffness device to alleviate the rotational oscillation existing in the many engineering applications, such as motor. Under such thought, the main purpose of this work is to characterize the nonlinear torque-angular displacement/angular velocity responses of an MRF based variable stiffness device in oscillatory motion. A rotational hysteresis model, consisting of a rotatory spring, a rotatory viscous damping element and an error function-based hysteresis element, is proposed, which is capable of describing the unique dynamical characteristics of this smart device. To estimate the optimal model parameters, a modified whale optimization algorithm (MWOA) is employed on the captured experimental data of torque, angular displacement and angular velocity under various excitation conditions. In MWOA, a nonlinear algorithm parameter updating mechanism is adopted to replace the traditional linear one, enhancing the global search ability initially and the local search ability at the later stage of the algorithm evolution. Additionally, the immune operation is introduced in the whale individual selection, improving the identification accuracy of solution. Finally, the dynamic testing results are used to validate the performance of the proposed model and the effectiveness of the proposed optimization algorithm.

• Applied Microscopy
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• v.24 no.2
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• pp.48-62
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• 1994

The acute irradiation effect on rat Purkinje cell was carried out. Anesthetized rats, weighing 200-250g each, were exposed their heads to the linear accelerator (ML-4MV) with the doses of 3,000 rads or 6,000 rads respectively. Irradiated rats were sacrificed by perfusion fixation under anesthesia, six hours, two days and six days following the irradiations. Rats were perfused with the fixative of 1% glutaraldehyde-1% paraformaldehyde solution (pH 7.4). Small pieces of cerebellar cortices were taken out. Tissue blocks were washed out, and were refixed in the 2% osmium tetroxide solution. After dehydration, tissues were embedded in the araldite mixture. Ultrathin sections stained with uranyl acetate-lead citrate solution, were examined with an electron microscope. The results observed were as follow; 1. Many dark Purkinje cells exhibited most severe cellular alterations on 6 hours. But after the 2 or 6 days, the cells exhibited only some alterations of cytoplasmic organelles. 2. Many granular and agranular endoplasmic reticula exhibited the fusion of cisterns. These reticular alterations were most severe on 6 hours following irradiation. But the alterations were hardly found on 6 days. 3. In the Golgi region, alterations including the adhesion of lamelliform cisterns, enlarged saccules, and increased number of vesicles, etc, were seen on 6 hours. But the Golgi complexes were almost recovered on 6 days. 4. Lysosomes were abundant on 6 hours or 2 days, but some residual bodies were found on 6 days. 5. Mitochondrial changes were also most severe at on hours, and they were recovered thereafter. From the results, it was concluded that the cerebellar Purkinje cells reacted to the high doses of irradiation by hyperactive protein synthesis, autolytic activities and energy metabolism. The reaction was most active in the early stage. It implies that motor-control function of Purkinje cells are severely disturbed in the early stage of irradiation.

• KIPS Transactions on Computer and Communication Systems
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• v.12 no.2
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• pp.85-92
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• 2023

Respiratory infections such as COVID-19 mainly occur within enclosed spaces. The presence or absence of abnormal symptoms of respiratory infectious diseases is judged through initial symptoms such as fever, cough, sneezing and difficulty breathing, and constant monitoring of these early symptoms is required. In this paper, image matching correction was performed for the RGB camera module and the thermal imaging camera module, and the temperature of the thermal imaging camera module for the measurement environment was calibrated using a blackbody. To detection the target recommended by the standard, a deep learning-based object recognition algorithm and the inner canthus recognition model were developed, and the model accuracy was derived by applying a dataset of 100 experimenters. Also, the error according to the measured distance was corrected through the object distance measurement using the Lidar module and the linear regression correction module. To measure the performance of the proposed model, an experimental environment consisting of a motor stage, an infrared thermography temperature screening system and a blackbody was established, and the error accuracy within 0.28℃ was shown as a result of temperature measurement according to a variable distance between 1m and 3.5 m.