• Journal of The Korean Society of Integrative Medicine
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• v.9 no.4
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• pp.191-200
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• 2021

Purpose : Chronic ankle instability can lead to problems in balance and gait due to weakness of the ankle muscles and decreased proprioceptive sensation. Balance training that stimulates proprioceptors is necessary to improve ankle stability. We aimed to compare the effects of unstable support balance exercises using whole body sonic vibration and an aero-step (TOGU) on proprioception and balance in individuals with unilateral functional ankle instability. Methods : Thirty-six participants with unilateral functional ankle instability were randomly recruited and divided into two groups (group 1 = sonic whole body vibration, group 2= TOGU). Individuals in each group participated in training for 5 weeks, 40 minutes per session, 5 times per week, and performed weight-bearing exercises in five postures on different unstable support surfaces. Proprioception was measured by digital inclinometer (Dualer IQ), and balance was measured by force platform (Biodex balance system). Results : Significant differences were observed in proprioception before and after intervention within both group (p<.05). Significant differences were also observed in the balance index before and after intervention within both groups (p<.05). Conclusion : As a result of this study, it is suggested that for individuals with ankle instability, unstable support surface training using a whole body sonic vibrator and TOGU can have a positive effects on proprioception and balance ability.

• Structural Engineering and Mechanics
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• v.80 no.6
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• pp.749-765
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• 2021

Suspension bridges bear large eccentric live loads in rush hours when most vehicles travel in one direction on the left or right side of the bridge. With the increasing number and weight of vehicles and the girder widening, the eccentric live load effect on the bridge behavior, including bending and distortion of the main girder, gets more pronounced, even jeopardizing bridge safety. This study proposes an analytical algorithm based on multi-catenary theory for predicting the suspension bridge responses to eccentric live load via the nonlinear generalized reduced gradient method. A set of governing equations is derived to solve the following unknown values: the girder rigid-body displacement in the longitudinal direction; the horizontal projection lengths of main cable's segments; the parameters of catenary equations and horizontal forces of the side span cable segments and the leftmost segments of middle span cables; the suspender tensions and the bearing reactions. Then girder's responses, including rigid-body displacement in the longitudinal direction, deflections, and torsion angles; suspenders' responses, including the suspender tensions and the hanging point displacements; main cables' responses, including the horizontal forces of each segment; and the longitudinal displacement of the pylons' tower top under eccentric load can be calculated. The response of an exemplar suspension bridge with three spans of 168, 548, and 168 m is calculated by the proposed analytical method and the finite element method in two eccentric live load cases, and their results prove the former's feasibility. The nonuniform distribution of the live load in the lateral direction is shown to impose a greater threat to suspension bridge safety than that in the longitudinal direction, while some other specific features revealed by the proposed method are discussed in detail.

• Korean Journal of Acupuncture
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• v.39 no.4
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• pp.132-141
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• 2022

Objectives : Some acupoints are commonly utilized to treat a variety of diseases. The acupoints appear to have a wide range of effects caused by several mechanisms. The purpose of this study is to investigate into the potential role of microRNAs (miRNAs) in the multipotent effects of individual acupoint stimulation. Methods : We examined the miRNA expressions in the dorsal root ganglia (DRG) of neuropathic or inflammatory pain rats following ST36 and GB34 electroacupuncture (EA) stimulation. Neuropathic pain was induced by L5 spinal nerve ligation. Inflammatory pain was induced by knee joint injection of Complete Freund's adjuvant (CFA). EA was given under gaseous anesthesia with the same parameters (1mA, 2Hz, 30 min) in 5 consecutive days. Pain behaviors and miRNA expressions were analyzed. Results : In rats with neuropathic and inflammatory pain, EA treatments significantly enhanced the paw withdrawal threshold and weight-bearing force. After nerve injury, 36 miRNAs were upregulated in the DRG of neuropathic rats, while EA downregulated 10 of them. Furthermore, 14 miRNAs were downregulated following nerve damage, while one was increased by EA. 15 miRNAs were increased in the DRG of inflammatory rats following CFA injection, while 5 were downregulated by EA. Furthermore, 17 miRNAs were downregulated following CFA injection, while 7 were increased by EA. The miRNAs rno-miR-335, rno-miR-381-5p, rno-miR-1306-3p, and rno-miR-1839-3p were regulated by EA in both models. Conclusions : In two pain models, EA applied to ST36 and GB34 regulated miRNA expression differently. There appeared to be both acupoint-specific and non-specific miRNAs, and miRNA regulation of differential protein expression may modulate a variety of EA mechanisms.

• Structural Engineering and Mechanics
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• v.86 no.2
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• pp.261-276
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• 2023

The use of the ordinary double nut (i.e., ODN) composed of a master nut (i.e., M-nut) and a slave nut (i.e., S-nut) is a highly efficient method to prevent bolts loosening. A novel double nut (i.e., FODN) composed of a master nut (i.e., M-nut) and flat slave nut (i.e., FS-nut) is proposed to save raw materials. The bolt fastening tests with single nut, ODN and FODN are performed to investigate the preload and counterbalance forces. Corresponding finite element analysis (FEA) models are established and validated by comparing the preload with the experimental results. The load-bearing capacity, the extrusion effect, and the contact stress of each engaged thread for ODN and FODN are observed by FEA. The experimental and simulated results revealed that the bolt fastening with double-nut has different load-transferring mechanisms from single-nut. Nevertheless, for double-nut/bolt assemblies, the FS-nut can provide load transfer that is like that of the S-nut, and the FODN is a reasonable and reliable fastening method. Furthermore, based on the theory of Yamamoto, a formula considering the extrusion effect is proposed to calculate the preload distribution of the double-nut, which is applicable to varying thicknesses of slave-nuts in double-nut/bolt assemblies.

• Earthquakes and Structures
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• v.24 no.5
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• pp.353-364
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• 2023

In this study, a method has been proposed for the static and dynamic nonlinear analysis of multi-storey buildings, which takes into account the contribution of axial deformations in vertical load-bearing elements, which are especially important in tall and narrow structures. Shear deformations on the shear walls were also taken into account in the study. The presented method takes into account the effects that are not considered in the fishbone and flexural-shear beam models developed in the literature. In the Fishbone model, only frame systems are modeled. In the flexural shear beam model developed for shear wall systems, shear deformations and axial deformations in the walls are neglected. Unlike the literature, with the model proposed in this study, both shear deformations in the walls and axial deformations in the columns and walls are taken into account. In the proposed model, multi-storey building is represented as a sandwich beam consisting of Timoshenko beams pieced together with a double-hinged beam. At each storey, the total moment capacities of the frame beams and the coupled beams in the coupled shear walls are represented as the equivalent shear capacity. On the other hand, The sums of individual columns and walls moment at the relevant floor level are represented as equivalent moment capacity at that floor level. At the end of the study, examples were solved to show the suitability of the proposed method in this study. The SAP2000 program is employed in analyses. In a conclusion, it is observed that among the solved examples, the proposed sandwich beam model gives good results. As can be seen from these results, it is seen that the presented method, especially in terms of base shear force, gives very close results to the detailed finite element method.

• Structural Engineering and Mechanics
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• v.87 no.3
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• pp.255-272
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• 2023

Spatial cable systems can provide more transverse stiffness and torsional stiffness without sacrificing the vertical bearing capacity compared with conventional vertical cable systems, which is quite lucrative for long-span earth-anchored suspension bridges' development. Higher economy highlights the importance of refined form-finding analysis. Meanwhile, the internal connection between the lateral and vertical sags has not yet been specified. Given this, an analytic algorithm of form-finding for the earth-anchored suspension bridge with spatial cables is proposed in this paper. Through the geometric compatibility condition and mechanical equilibrium condition, the expressions for cable segment, the recurrence relationship between catenary parameters and control equations of spatial cable are established. Additionally, the nonlinear general reduced gradient method is introduced into fast and high-precision numerical analysis. Furthermore, the analytic expression of the lateral and vertical sags is deduced and discussed. This is very significant for the space design above the bridge deck and the optimization of the sag-to-span ratio in the preliminary design stage of the bridge. Finally, the proposed method is verified with the aid of two examples, one being an operational self-anchored suspension bridge (with spatial cables and a 260 m main span), and the other being an earth-anchored suspension bridge under design (with spatial cables and a 500 m main span). The necessity of an iterative calculation for hanger tensions on earth-anchored suspension bridges is confirmed. It is further concluded that the main cable and their connected hangers are in very close inclined planes.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.1
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• pp.106-111
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• 2024

A triboelectric nanogenerator is a promising energy harvester operated by the combined mechanism of electrostatic induction and contact electrification. It has attracting attention as eco-friendly and sustainable energy generators by harvesting wasting mechanical energies. However, the power generated in the natural environment is accompanied by low frequencies, so that the output power under such input conditions is normally insufficient amount for a variety of industrial applications. In this study, we introduce a non-contact rotational triboelectric nanogenerator using pedaling and gear systems (called by P-TENG), which has a mechanism that produces high power by using rack gear and pinion gear when a large force by a pedal is given. We design the system can rotate the shaft to which the rotor is connected through the conversion of vertical motion to rotational motion between the rack gear and the pinion gear. Furthermore, the system controls the one directional rotation due to the engagement rotation of the two pinion gears and the one-way needle roller bearing. The TENG with a 2 mm gap between the rotor and the stator produces about the power of 200 ㎼ and turns on 82 LEDs under the condition of 800 rpm. We expect that P-TENG can be used in a variety of applications such as operating portable electronics or sterilizing contaminated water.

• Journal of the Korean Geosynthetics Society
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• v.20 no.4
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• pp.85-93
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• 2021

The seventy percentage of Korean Peninsular is covered by the mountainous area, and the depth of west sea and south sea is relatively shallow. Therefore, a large scale land reclamation from the sea has been implemented for the construction of industrial complex, residental area, and port and airport facilities. The common problem of reclaimed land is consisted of soft ground, and hence it has low load bearing capacity as well as excessive settlement upon loading on the ground surface. The hollow concrete block has been used to reinforce the loose and soft foundation soil where the medium-high apartment or one-story industrial building is being planned to be built. Recently the earthquakes with the magnitude of 4.0~5.0 have been occurred in the west coastal and southeast coastal areas. Lee (2019) reported the advantages of hollow concrete block reinforced shallow foundation through the static laboratory bearing capacity tests. In this study, the dynamic behavior of hollow concrete block reinforced sandy ground with filling the crushed stone in the hollow space has been investigated by the means of shaking table test with the size of shaking table 1000 mm × 1000 mm. Three types of seismic wave, that is, Ofunato, Hachinohe, Artificial, and two different accelerations (0.154 g, 0.22 g) were applied in the shaking table tests. The horizontal displacement of structure which is situated right above the hollow concrete block reinforced ground was measured by using the LVDT. The relative density of soil ground are varied with 45%, 65%, and 85%, respectively, to investigate the effectiveness of reinforcement by hollow block and measured the magnitude of lateral movement, and compared with the limit value of 0.015h (Building Earthquake Code, 2019). Based on the results of shaking table test for hollow concrete block reinforced sandy ground, honeycell type hollow block gives a large interlocking force due to the filling of crushed stone in the hollow space as well as a great interface friction force by the confining pressure and punching resistance along the inside and outside of hollow concrete block. All these factors are contributed to reduce the great amount of horizontal displacement during the shaking table test. Finally, hollow concrete block reinforced sandy ground for shallow foundation is provided an outstanding reinforced method for medium-high building irrespective of seismic wave and moderate accelerations.

• Journal of the Korean GEO-environmental Society
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• v.13 no.1
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• pp.53-61
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• 2012

In this study, the research on MC anchor has been developed as composite type has done. MC anchor exerts bearing pressure on pre-bored hole where the end fixing device is expanded. Therefore, the uplift capacity is to be increased and it has the characteristics that the anchor body is not eliminated from the ground even if the grouting is not carried out properly. Furthermore, it reduces the loss of tension and raises the construction availability by inserting the reinforced bar as well as the anchor cable, while it can improve the long-term stability because the nail is expected to play the role when the loss of the anchor cable is occurred in a long-term. However, because the resistance mechanism of the compound anchor such as MC anchor is different from friction anchor, the estimation method of the uplift capacity by the frictional force of the ground and the grout is not proper. Particularly, in domestic cases, the problem to overestimate or underestimate the uplift capacity is expected because the design method considering the soil characteristics about the compound anchor has not been developed. Therefore, in this study, in order to evaluate the characteristics of MC anchor and a kind of compound anchor, we measured the uplift, the tension and the creep by nine anchors tests in shale ground that the fluctuation of the strength is great. In addition, we analyzed the test result comparing to the result of the general friction anchor and evaluated the characteristics of MC anchor movement to gather the results. As a result of the test, we found the effect that the uplift capacity is increased in shale ground comparing to the general friction anchor.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.263-274
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• 2018

In this study, the applicability and external/internal stability of a MSEW abutment with a slab were investigated. Structural analysis of slab bridges between 10 ~ 20.0 m and thicknesses of 0.7 ~ 0.9 m was carried out to calculate the reaction forces due to dead and live loads acting on the bridge supports. The slab bridge with a length of 20.0 m satisfied the allowable contact pressure of 200 kPa for the true MSEW abutment. Because the external stability of the true MSEW abutment was dominated by the geometry of the MSE wall, the change in the factor of safety due to the load of the super-structure is small. Because the stiffness of the foundations is fixed and the load of the super-structure is increased, the factor of safety of the bearing capacity was reduced. As the load of the super-structure was increased, the horizontal earth pressure of the true MSEW abutment increased greatly. As a result, the pullout and fracture of the uppermost reinforcement, which are the factors of safety, did not meet the design criteria. Therefore, it is necessary to increase the pullout resistance and the long-term allowable tensile force of the reinforcement placed on the top of the reinforced soils to ensure efficient design and performance of a true MSEW abutment.