• Earthquakes and Structures
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• v.11 no.5
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• pp.905-924
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• 2016

Several two-dimensional analytical beam column joint models with varying complexities have been proposed in quantifying joint flexibility during seismic vulnerability assessment of non-ductile reinforced concrete (RC) frames. Notable models are the single component rotational spring element and the super element joint model that can effectively capture the governing inelastic mechanisms under severe ground motions. Even though both models have been extensively calibrated and verified using quasi-static test of joint sub-assemblages, a comparative study of the inelastic seismic responses under nonlinear time history analysis (NTHA) of RC frames has not been thoroughly evaluated. This study employs three hypothetical case study RC frames subjected to increasing ground motion intensities to study their inherent variations. Results indicate that the super element joint model overestimates the transient drift ratio at the first story and becomes highly un-conservative by under-predicting the drift ratios at the roof level when compared to the single-component model and the conventional rigid joint assumption. In addition, between these story levels, a decline in the drift ratios is observed as the story level increased. However, from this limited study, there is no consistent evidence to suggest that care should be taken in selecting either a single or multi component joint model for seismic risk assessment of buildings when a global demand measure such as maximum inter-storey drift is employed in the seismic assessment framework.

• The Journal of Korea Robotics Society
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• v.11 no.3
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• pp.163-171
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• 2016

A modular manipulator in serial-chain structure usually consists of a series of modularized revolute joint and link modules. The geometric shapes of these modules affect the number of possible configurations of modular manipulator after assembly. Therefore, it is important to design the geometry of the joint and link modules that allow various configurations of the manipulators with minimal set of modules. In this paper, a new 1-DoF(degree of freedom) joint module and simple link modules are designed based on a methodology of joint configurations using a series of Rotational(type-R) and Twist(type-T) joints. Two of the joint modules can be directly connected so that two types of 2-DoFs joints could be assembled without a link module between them. The proposed geometries of joint and link modules expand the possible configurations of assembled modular manipulators compared to existing ones. Modular manipulator system of this research can be a cornerstone of user-centered markets with various solution but low-cost, compared to conventional manipulators of fixed-configurations determined by the provider.

• Journal of Technologic Dentistry
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• v.39 no.3
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• pp.187-196
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• 2017

Purpose: The purpose of this study was to investigate the factors contributing to temporomandibular joint disorder symptoms. Methods: The survey was conducted from May 1 to June 10 2017 against college students(120 males and 123 females) in Daejeon and Gangwon who understood the purpose of this study and agreed to participate. Results: First, The most frequent symptom of temporomandibular joint disorders is noises from the joint (male 45%, female 61.8%), followed by headache or neck pain (male 25.8%, female 52.8%). There was shown a significant difference by gender in all items except for jaw dropping, poor alignment of teeth and trauma(p<0.05). Second, Looking into the correlation between stress and subjective symptoms of Temporomandibular joint disorders, The stress of Temporomandibular joint disorders showed more significant relation with realistic issues such as academic task, economic burden (e.g., treatment cost), future career, and life values rather than aspect of social relationship(p<0.01). Conclusion: As a result of analyzing variables to understand the influence of stress on temporomandibular joint disorders, the accumulated number of bad habits, stress and temporomandibular joint disorders showed a significantly positive correlation with one another (p<0.05). In other words, the higher the stress level the severe the temporomandibular joint disorders; the more the bad habits the severe the temporomandibular joint disorders;

• The Journal of Korea Robotics Society
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• v.13 no.2
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• pp.92-96
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• 2018

In this paper, a soft robotic arm which can prevent impact injury during human-robot interaction is introduced. Two degrees of freedom joint are required to realize free movement of the robotic arm. A robotic joint concept with a single degree of freedom is presented using simple inflatable elements, and then extended to form a robotic joint with two degrees of freedom joint using similar manufacturing methods. The robotic joint with a single degree of freedom has a joint angle of $0^{\circ}$ bending angle when both chamber are inflated at equal pressures and maximum bending angles of $28.4^{\circ}$ and $27.1^{\circ}$ when a single chamber if inflated. The robotic joint with two degrees of freedom also has a bending angle of $0^{\circ}$ in both direction when all three chambers are inflated at equal pressures. When either one or two chambers were pressurized, the robotic joint performed bending towards the uninflated chambers.

• Journal of the Korean GEO-environmental Society
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• v.17 no.1
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• pp.29-37
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• 2016

This study examined the magnitude and distribution of earth pressure on the support system in a jointed rock mass due to the different joint spacing as well as varying the rock type and joint condition (joint shear strength and joint inclination angle). Based on a physical model test and its numerical simulation, a series of numerical parametric analyses were conducted using a discrete element method. The results showed that the magnitude and distribution of earth pressure were strongly affected by the different joint spacing as well as the rock type and joint condition. In addition, the study results were compared with Peck's earth pressure for soil ground, which indicated that the earth pressure in a jointed rock mass could be considerably different from that in soil ground. The study suggests that the joint spacing as well as the rock type and joint condition are important factors affecting the earth pressure in a jointed rock mass and they should be considered when designing a support system in a jointed rock mass.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.2
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• pp.154-158
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• 2013

Expansion joint has been utilized in many areas including automotive bellows for exhaust system. Usage of expansion joint has been increased due to its inherent flexibility and excellent anti-vibration property. Simple shape of expansion joint is modeled to understand the behavior of joint system. 27 design cases using 3 design factors with 3 levels are constructed by design of experiment. Each case is simulated to find the most influential design factors. Response for this study, maximum stress in the expansion joint, has been used to determine main design factors of joint. Among the 3 design factors, factor B has affected greatly a response in the formation of optimum shape of joint. Also, interaction factor, $A{\times}B$, has also showed its influence to the response of joint. This study showed that design of experiment combined with finite element analysis could be used in the design decision process effectively in the design of expansion joint.

• The Journal of Korean Physical Therapy
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• v.3 no.1
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• pp.97-108
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• 1991

The purpose of this article is to know the standard figures of joint range of motion, in conjuction with age and sen, for normal adults. The results of assessment and analysis io shoulder and hip joint range of motion are as follows : 1) The average shoulder joint range of motion in normal adults are $160.5^{\circ}$ in flexion, $53.5^{\circ}$ in extension, $159.3^{\circ}$ in adduction, $62.3^{\circ}$ in internal rotation, $83.9^{\circ}$ in external rotation, The average hip joint range of motions are $116.8^{\circ}$ in flexion, $16.1^{\circ}$ in extension, $41.1^{\circ}$ in abduction, $33.8^{\circ}$ in abduction, $40.0^{\circ}$ in interne rotation, $41.2^{\circ}$ in external rotation. 2) There is no significant difference in shoulder and hip joint range of motion between male and female (p>0.05). 3) As to the inter-relation in age and range of motion, the left flexion and extension, internal rotation and right extension in shoulder joint is decreased gradually with increasing age, and left flexion (knee flexion, knee extension) and right flexion (knee extension) in hip joint is decreased with increasing age (p<0.01). 4) Relating to age and sex, the twenties male shows highest range of motion in shoulder and hip joint, with .the fifties female shows, lowest range of motion.

• Tunnel and Underground Space
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• v.21 no.5
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• pp.386-393
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• 2011

This study suggests an algorithm for estimating joint diameter distribution in rock mass from the joint trace length distribution around a circular tunnel. For estimating the joint diameter distribution, the concept of Joint Center Volume (JCV) suggested by Song. (2005) was applied and the calculation method of JCV for the cylindrical window survey was developed by using the complete survey method. The estimated joint diameter distribution was verified against the original joint diameter distribution by Monte-Carlo simulation. It was observed that the estimated joint diameter distribution was converged to the original joint diameter distribution with less than 20% of error.

• Structural Engineering and Mechanics
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• v.77 no.4
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• pp.509-521
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• 2021

The neighbouring gaps at the mortise-tenon joint in traditional timber structure, which leads to the complexity of the joint, are considered to impair the mechanical performance of the joint. In this paper, numerical simulation of loose joint was conducted to examine the deformation states, stress distributions, and bearing capacities, which was verified by full-scale test. On the basis of the experimental and numerical results, a simplified mechanics model with gaps has been proposed to present the bending capacity of the loose joint. Besides, the gap effects and parameter studies on the influences of tenon height, friction coefficient, elastic modulus and axial load were also investigated. As a result, the estimated relationship between moment and rotation angle of loose joint showed the agreement with the numerical results, demonstrating validity of the proposed model; The bending bearing capacity and rotational stiffness of loose joint had a certain drop with the increasing of gaps; and the tenon height may be the most important factor affecting the mechanical behaviors of the joint when it is subjected to repeated load; Research results can provide important references on the condition assessments of the existing mortise-tenon joint.

• International journal of advanced smart convergence
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• v.4 no.1
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• pp.145-153
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• 2015

Friction Stir Welding (FSW) is a solid state welding that could successfully weld the difficult-to-weldmaterials such as an aluminum alloy. In this welding process, the stirrer of the welding tool is one of the important factors for producing the perfect sound joint that indicates the higher joint strength. So, this report aims to apply the friction stir welding using various stirrer geometries to weld the AA6063-T1 aluminum alloy butt joint, investigates the mechanical properties of the joint and then compares the mechanical properties with the microstructure of the joint. An experiment was started by applying the friction stir welding process to weld a 6.3 mm thickness of AA6063-T1 aluminum alloy butt joint. A study of the stirrer geometries effect such as a cylindrical geometry, a cone geometry, a left screw geometry and a right screw geometry at a rotational speed of 2000 rpm and a welding speed of 50-200 mm/min was performed. The mechanical properties such as a tensile strength and a hardness of the joint were also investigated and compared with the microstructure of the joint. The results are as follows. A variation of FSW Stirrer shape directly affected the quality AA6063-T1 aluminum alloy butt joint. A cylindrical stirrer shape and a cone stirrer shape produced the void defect at the bottom part of the weld metal and initiated the failure of the joint when the joint was subjected to the load during the tensile test. Left and right screw stirrer shapes gave the sound joint with no void defect in the weld metal and affected to increase the joint strength that was higher than that of the aluminum base metal.