• The Journal of Advanced Prosthodontics
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• v.13 no.3
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• pp.172-179
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• 2021

Purpose. This intra-patient retrospective study of up to 10 years evaluated the clinical success and risk factors of 6- and 8-mm long implants and their respective prostheses. Materials and Methods. The sample consisted of patients treated at a Military Polyclinic dental service, who received both 6- and 8-mm long tissue level implants in the posterior region of the same arch. Data were collected from the dental charts, clinical and radiographic exams, self-report of sleep bruxism, measurement of maximum occlusal force, and clinical crown-to-implant (C/I) ratio. Data were analyzed by descriptive and inferential statistics with univariate and hierarchical multivariate models, at the 0.05 significance level. Results. The 30 patients (27 women) had 85 implants and 83 prostheses. Two implants were lost before prosthesis installation (implant survival: 97.6%). Ten events of prosthetic complication (screw tightening loss) occurred in five patients (success rate: 87.9%) in a single moment. Only the variable C/I ratio had a significant effect for repairable prosthesis complication (P<.05). Conclusion. The results suggest that 6- and 8-mm long implants have similar long-term clinical success for implants and prostheses.

• Journal of the Korean Society of Physical Medicine
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• v.16 no.1
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• pp.17-22
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• 2021

PURPOSE: This study examined the correlations between gait, static balance, and pelvic inclination in patients with chronic stroke. METHODS: Twenty-two chronic stroke patients were included in this study. The subjects participated in gait, static balance, and pelvic inclination tests. In the gait measurement, the cadence and gait velocity were measured, and the average of three trials was calculated and recorded. The static balance was measured using a force platform. The data was captured for ten seconds, and five successful trials were recorded. Pelvic inclination in the sagittal plane was measured using a palpation meter. For data processing, a KolmogorovSmirnov test was used to determine the type of distribution for all variables. Pearson's correlation coefficient was used for correlation analysis. The correlations among the gait, static balance, and pelvic inclination was calculated. The level of significance was .05. RESULTS: Significant negative correlations were observed between the gait variables (cadence, velocity) and static balance variables (COP path length, COP average velocity, and 95% confidence ellipse area) (p < .05). On the other hand, there was no significant correlation between pelvic inclination and gait or between the pelvic inclination and static balance variables. CONCLUSION: Significant correlations were observed between the gait function and static balance. On the other hand, there were no significant correlations between the pelvic inclination and gait and static balance. These results suggest that the pelvic inclination is not an important consideration for increasing the gait function and static balance.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.1
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• pp.25-30
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• 2021

The differential gear system is a device designed to distribute the driving force of both vehicle wheels and control the rotational speed when the vehicle turns on a curve. The differential device consists of a differential gear case, a ring gear, and a pressure ring. A differential pinion gear and side gear are mounted on the differential pinion shaft inside the differential gear case. In this study, a pin press-fitting device that mounts the pinier gear and side gear to the differential pinion shaft in the differential gear case was designed, and a jig device for pin press-fitting using servo press was developed. In addition, by precisely measuring the pin press-in load and press-in distance according to the pin hole diameter of the differential gear shaft, the optimization of the pin pressin process was established.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.6
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• pp.345-352
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• 2020

This study aims to investigate the crabbing motion of the research vessel "NARA" by full-scale maneuvering trials. The crabbing test method refers to ITTC recommended procedures and guidelines. In order to minimize the fluctuation of the heading angle due to the external force acting on the hull during the pure lateral motion, the tests are conducted using the dynamic positioning system applied to the ship. The test results are analyzed by applying a low-pass filter to remove the noise included in the measurement data. Three conditions are set to define the steady state of crabbing motion. The index to be derived from the crabbing test is quantitatively presented. The ship is confirmed to be capable of the lateral motion of up to 0.844m/s in Beaufort 3.

• Journal of the Korean Society of Visualization
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• v.19 no.3
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• pp.106-114
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• 2021

In the present study, we investigate the flow characteristics of a paraglider canopy with leading-edge tubercles by performing force measurement and surface flow visualizations. The experiment is conducted at Re = 3.3×10⁵ in a wind tunnel, where Re is the Reynolds number based on the mean chord length and the free-stream velocity. The canopy model with leading-edge tubercles has flow characteristics of a two-step stall, showing an earlier onset of the first stall than the canopy model without leading-edge tubercles. However, the main stall angle of the tubercled model is much larger than that of the canopy model without tubercles, resulting in a higher aerodynamic performance at high angles of attack. The delay in the main stall is ascribed to the suppression of separation bubble collapse around the wingtip at high angles of attack.

• IEMEK Journal of Embedded Systems and Applications
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• v.17 no.3
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• pp.149-155
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• 2022

This paper proposes a method for estimating the road surface condition and tilt angle using an inertial measurement unit (IMU) to improve the safety in the use of mobility aids for the elderly. The measurements of the accelerometers of the IMU usually include the accelerations caused by not only the gravitational force but also linear and rotational motions. Thus, the gravitational accelerations are first extracted using several physical constraints and then incorporated into the Kalman filter to estimate the tilt angle. In addition, because the magnitudes of the accelerations produced by the rotational motions (roll and pitch motions) vary with the road surface condition, a criterion based on such accelerations is presented to classify the condition of the road surface. The obtained road surface condition and tilt angle are finally combined to provide the safety information (e.g., safe, warning, and danger) for the user to improve the walking safety. Experiments were carried out and the results showed that the proposed method can provide the condition of the road surface, the tilt of the road surface, and the safety information correctly.

• Molecules and Cells
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• v.45 no.1
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• pp.26-32
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• 2022

Living cells generate, sense, and respond to mechanical forces through their interaction with neighboring cells or extracellular matrix, thereby regulating diverse cellular processes such as growth, motility, differentiation, and immune responses. Dysregulation of mechanosensitive signaling pathways is found associated with the development and progression of various diseases such as cancer. Yet, little is known about the mechanisms behind mechano-regulation, largely due to the limited availability of tools to study it at the molecular level. The recent development of molecular tension probes allows measurement of cellular forces exerted by single ligand-receptor interaction, which has helped in revealing the hitherto unknown mechanistic details of various mechanosensitive processes in living cells. Here, we provide an introductory overview of two methods based on molecular tension probes, tension gauge tether (TGT), and molecular tension fluorescence microscopy (MTFM). TGT utilizes the irreversible rupture of double-stranded DNA tether upon application of force in the piconewton (pN) range, whereas MTFM utilizes the reversible extension of molecular springs such as polymer or single-stranded DNA hairpin under applied pN forces. Specifically, the underlying principle of how molecular tension probes measure cell-generated mechanical forces and their applications to mechanosensitive biological processes are described.

• Smart Structures and Systems
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• v.30 no.4
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• pp.397-410
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• 2022

It is essential to monitor the working conditions of bolt-connected joints, which are widely used in various kinds of steel structures. The looseness of bolts may directly affect the stability and safety of the entire structure. In this study, a guided wave-based method for bolt looseness detection and localization is presented for a joint structure with multiple bolts. SH waves generated and received by a small number (two pairs) of magnetostrictive transducers were used. The bolt looseness index was proposed based on the changes in the reconstructed responses excited by the time reversal signals of the measured unit impulse responses. The damage locations and local damage severities were estimated using the damage indices from several wave propagation paths. The back propagation neural network (BPNN) technique was employed to identify the local damages. Numerical and experimental studies were conducted on a lap joint with eight bolts. The results show that the total damage severity can be successfully detected under the effect of external force and measurement noise. The local damage severity can be estimated reasonably for the experimental data using the BPNN constructed by the training patterns generated from the finite element simulations.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2003.10a
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• pp.54-54
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• 2003

DLC films were deposited on Si(100) substrates by inductively coupled plasma (ICP) assisted chemical vapor deposition (CVD). A mixture of acetylene (C$_2$H$_2$) and argon (Ar) gases was used as the precursor and plasma source, respectively. The structure of the films was characterized by the Raman spectroscopy. Results from the Raman spectroscopy analysis indicated that the property change of the DLC films is due to the sp$^3$ and sp$^2$ ratio in the films under various conditions such as ICP power, working pressure and RF substrate bias. The hydrogen content in the DLC films was determined by an electron recoil detector (ERB). The roughness of the films was measured by atomic force microscope (Am). A microhardness tester was used for the hardness and elastic modulus measurement. The DLC film showed a maximum hardness of 37㎬. In this work, the relationship between deposition parameters and mechanical properties were discussed.

• PNF and Movement
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• v.20 no.1
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• pp.125-134
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• 2022

Purpose: The aim of this study was to establish an association between grip strength and gait variability in the elderly. Methods: The participants in this experiment (n = 20) were aged 65 or older. Power grip and lateral pinch forces were obtained in grip strength tests, and spatiotemporal gait parameters were collected from IMU sensors during 6 min actual walking to test the gait of participants. The collected gait parameters were converted to coefficient of variation (CV) values. To confirm the association between grip strength and gait variability, a partial correlation analysis was conducted in which height, weight, and gait speed were input as controlling variables. Results: Grip power showed a significant negative correlation with the stride length CV (r = -0.52), and the lateral pinch force showed a significant negative correlation with the stance CV (r = -0.65) and swing CV (r = -0.63). Conclusion: This study reveals that gait variability decreases as grip strength increases, although height, weight, and gait speed were controlled. Thus, grip strength testing, a simple aging evaluation method, can help identify unstable gait in older adults at risk of falling, and grip strength can be utilized as a non-invasive measurement method for frailty management and prevention.