• Earthquakes and Structures
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• v.24 no.3
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• pp.205-215
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• 2023

Currently, many studies are underway at home and abroad on the seismic performance evaluation and dry construction method of the masonry structure. In this study, a dry stack masonry wall system without mortar using concrete blocks is proposed, and investigate the seismic performance of dry filling wall frames through experimental studies. First, two types of standard blocks and key blocks were designed to assemble dry walls of concrete blocks. And then, three types of experiments were manufactured, including pure frame, 1/2 height filling wall frame, and full height filling wall frame, and cyclic load experiments in horizontal direction were performed to analyze crack patterns, load displacement history, rebar deformation yield, effective stiffness change, displacement ductility, and energy dissipation capacity. According to the experimental results, the full height filling wall frame had the largest horizontal resistance against the earthquake load and showed a high energy dissipation capacity. However, the 1/2 height filling wall frame requires attention because the filling wall constrains the effective span of the column, limiting the horizontal displacement of the frame. In addition, the concrete block was firmly assembled in the vertical direction of the wall as the horizontal movement between the concrete blocks was allowed within installation margin, and there was no dropping of the assembled concrete block.

• Steel and Composite Structures
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• v.42 no.5
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• pp.699-710
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• 2022

This work presents a comprehensive study on the surface energy effect on the axial frequency analyses of AFGM nanorods in cylindrical coordinates. The AFGM nanorods are considered to be thin, relatively thick, and thick. In thin nanorods, effects of the inertia of lateral motions and the shear stiffness are ignored; in relatively thick nanorods, only the first one is considered; and in thick nanorods, both of them are considered in the kinetic energy and the strain energy of the nanorod, respectively. The surface elasticity theory which includes three surface parameters called surface density, surface stress, and surface Lame constants, is implemented to consider the size effect. The power-law form is considered for variation of the material properties through the axial direction. Hamilton's principle is used to derive the governing equations and boundary conditions. Due to considering the surface stress, the governing equation and boundary condition become inhomogeneous. After homogenization of them using an appropriate change of variable, axial natural frequencies are calculated implementing harmonic differential quadrature (HDQ) method. Comprehensive results including effects of geometric parameters and various material properties are presented for a wide range of boundary condition types. It is believed that this study is a comprehensive one that can help posterities for design and manufacturing of nano-electro-mechanical systems.

• Tribology and Lubricants
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• v.38 no.2
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• pp.63-69
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• 2022

In this research, the rotordynamic characteristics of the labyrinth seal with and without swirl brake were predicted using the computational fluid dynamic (CFD) model. Based on previous studies, a simple swirl brake consisting of square vanes without stagger angle is designed and placed in front of the seal inlet. The rotating frame of reference is utilized to consider the whirling motion of the rotor in the steady-state analysis since the whirling motion is transient behavior in nature. CFD analysis was performed in the range of -1 to 1 pre-swirl ratio for a given seal and swirl brake design and operating conditions. The CFD analysis result shows that the swirl brake effectively reduces the pre-swirl since the circumferential fluid velocity of labyrinth seal with swirl brake was lower than that without swirl brake. The cross-coupled stiffness coefficient, which is greatly affected by the circumferential fluid velocity, increased with an increasing pre-swirl ratio in a seal without a swirl brake but showed a low value in a seal with a swirl brake. The change in the damping coefficient was relatively small. The effective damping coefficient of the labyrinth seal with swirl brake was generally constant and showed a higher value than the labyrinth seal without swirl brake.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2A
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• pp.273-284
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• 2006

In this study, After considering the general characteristic of Near Fault Ground Motion, the inelastic response spectrum is made to evaluate using the change of ductility and yield stiffness coefficient according to the inelastic behavior of structures which couldn't be examined through the elastic response spectrum. It is conducted to the elastic and inelastic time history analysis about the long period structure which could reflect the characteristic of Near Fault Ground Motion with the best and it is also examined the aspect of response distribution about the input data. Moreover, the response characteristic of structure is analyzed by investigating the plastic hinge for the purpose of grasp about the inelastic behavior of structure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.5A
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• pp.417-424
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• 2010

The dynamic properties of laminated rubber bearings used as isolators in structures could be significantly deteriorated because of the change of microstructure in rubber caused by thermal aging. As a result, a catastrophic failure of bridges and buildings unexpectedly occurs when they are subjected to earthquake attack. Here, the dynamic properties of laminated rubber bearings before and after different of compression-shear loading and repeated cycles loadings, ultimated failure test with thermal aging were first measured and compared to each other. The experimental results, the effects of thermal aging on the shear stiffness, energy absorption, and equivalent damping coefficient of laminated rubber bearings are investigated. It is found that the deterioration of dynamic properties of laminated rubber bearings caused by thermal aging is significant and should be taken into account in designing rubber bearings.

• Korean Journal of Applied Biomechanics
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• v.33 no.2
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• pp.52-61
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• 2023

Objective: This study aimed to investigate the effect of a combined functional intervention program on the pain-related questionnaire, the erector spinae contractile properties, and trunk extensor strength of prime-aged females with non-specific chronic low back pain. Method: 16 (female: 16) prime-aged subjects (age: 60.88 ± 6.09 years, height: 158.16 ± 5.58 cm, weight: 59.05 ± 9.44 kg) participated in this study. Results: Except for Tampa Scale of Kinesiophobia all pain-related questionnaires revealed a significant decrease after the intervention program (p<.001). Tensiomyography of the erector spinae revealed a significant post-intervention program increase in the maximum radial displacement (p<.05) and velocity of contraction (p<.05), however, there wasn't a significant post-intervention program change in the contraction time. Additionally, Trunk extensor strength showed a significant increase post-intervention program (p<.001). Conclusion: Our results indicated that the combined functional intervention program positively changed pain-related questionnaires and reduced erector spinae muscle stiffness, increasing the velocity of erector spinae contraction. Additionally, improved the trunk extensor strength.

• Structural Engineering and Mechanics
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• v.88 no.6
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• pp.599-608
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• 2023

The present study is focused on instigation of the nonlinear mechanical behavior of reinforced concrete beams considering different types of FRP bars through nonlinear finite element simulations. To explore the impact of the FRP reinforcement type and geometry on the nonlinear mechanical behavior of reinforced beam, intensive parametric studies are carried out and discussed. Twenty models were carried out based on the finite element software (ABAQUS). The concrete damage plasticity model was considered. Four types of fiber polymer bars, CFRP, GFRP, AFRP and BFRP as longitudinal reinforcement for concrete beam were used. The validation of numerical results was confirmed by experimental as well as numerical results, then the parametric study was conducted to evaluate the effect of change in different parameters, such as bar diameter size, type of FRP bars and shear span length. All results were analyzed and discussed through, load-deflection diagram. The results showed that the use of FRP bars in rebar concrete beam improves the beam stiffness and enhance the ultimate load capacity. The load capacity enhanced in the range of (20.44-244.47%) when using different types of FRP bars. The load-carrying capacity of beams reinforced with CFRP is the highest one, beams reinforced with AFRP is higher than that reinforced with BFRP but beams reinforced with GFRP recorded the lowest load of capacity compered with other beams reinforced with FRP Bars.

• Journal of the Semiconductor & Display Technology
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• v.22 no.4
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• pp.87-92
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• 2023

As the elderly population increases, the number of patients with various joint diseases, including degenerative arthritis, is steadily increasing. CPM medical devices are needed to effectively treat degenerative arthritis that is common in the elderly population. Domestic CPM medical devices have limited functions and are highly dependent on imports for expensive imported medical devices. To solve this problem, we designed a ROM measurement function using a current sensor that is not present in existing composite joint CPM medical devices. The algorithm was designed using the fact that the force caused by joint stiffness greatly increases the current flowing through the DC motor. In addition, the need for digital healthcare in the medical field is gradually expanding as the proportion of chronically ill patients increases due to the spread of the non-face-to-face economy due to COVID-19 and the aging population. Therefore, this paper aims to improve the performance of CPM medical devices by allowing real-time confirmation of rehabilitation exercise information and operation range measurement results in accordance with digital healthcare trends through a Bluetooth application developed as an Android studio.

• Physical Therapy Korea
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• v.30 no.4
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• pp.275-280
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• 2023

Background: Although warm-ups before exercise are widely accepted, research on sex differences in improving hamstring flexibility is limited. Differences in the physical and physiological characteristics between males and females may result in different responses to warm-ups. Objects: This study aimed to examine sex differences in the effects of specific warm-up on hamstring flexibility. Methods: This study included 24 young adults with hamstring tightness. The participants performed five maximal knee extensions and flexions at 90° flexion of the hip, and the maximal knee extension angle was measured in real-time using a smartphone clinometer application. Results: The groups did not significantly affect the maximal knee extension angle but showed a significant effect for repetition (p = 0.002) and group-repetition interaction (p = 0.002). Males had no significant change in hamstring flexibility; however, females showed a significant increase in flexibility in the 5^th trial compared with the 1^st trial (p = 0.041). These results demonstrated sex-specific differences in flexibility improvement over time. Conclusion: The findings of this study suggest that specific warm-up can successfully improve hamstring flexibility in females. This may be due to various factors, such as muscle stiffness of the lower extremity, estrogen levels, and temperature sensitivity. In clinical settings, specific warm-up might be helpful for females who participate in sports or activities, such as running or jumping, which require a full range of motion in the hip and knee joints.

• Journal of Acupuncture Research
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• v.41 no.2
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• pp.129-134
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• 2024

Knee osteoarthritis (KOA) is a prevalent degenerative joint disease causing significant pain and dysfunction. This case report presents the use of electromagnetic acupuncture utilizing a Whata 153 device generating a magnetic field to enhance acupuncture stimulation for the treatment of KOA. A 69-year-old female diagnosed with KOA experienced a reduction in pain (numerical rating scale score from 7 to 4), improved gait, and decreased stiffness and swelling after daily electromagnetic acupuncture treatments during hospitalization. In addition, the Korean Western Ontario and McMaster Universities Osteoarthritis Index scoreimproved from 20 to 14, and the patient rated her overall improvement as "significantly improved" on the patient's global impression of change scale. Although these findings suggest potential benefits of electromagnetic acupuncture for KOA, the case report design limits its generalizability. More controlled trials are warranted to confirm the efficacy and safety of electromagnetic acupuncture as a treatment of KOA.