• Journal of Institute of Control, Robotics and Systems
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• v.22 no.10
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• pp.817-825
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• 2016

In this paper, we introduce a flexible gripper that we have engineered to precisely pinch in parallel and compliantly grasp objects. As found in most conventional industrial grippers, the parallel pinching property is essential for precise manipulation. On the other hand, the grippers with a flexible structure are more adept at grasping objects with arbitrary shapes and softness. To achieve these disparate properties, we introduce a flexible gripper mechanism composed of multiple flexible beam structures. Utilizing these beam structures, the proposed gripper is able to grasp arbitrarily shaped objects. Additionally, a unique combination of flexible beams enables the gripper to pinch objects using the parallel fingertips for enhanced precision. A detailed description of the proposed mechanism is provided, and an analysis of the strength and stiffness of the fingertip and finger body is presented. The Results section compares the theoretical and experimental analyses and verifies the properties and performance of the proposed gripper.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.7
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• pp.568-577
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• 2000

In this paper for an object grasped by a robot hand to work in stiffness control domain we first investigate the number of fingers for successful stiffness modulation in the object operational space. Next we propose a new compliance control method for robot hands which consist of two steps. RIFDS(Resolved Inter-Finger Decoupling Solver) is to decompose the desired compliance characteristic specified in the op-erational space into the compliance characteristic in the fingertip space without inter-finger coupling and RIJDS(Resolved Inter-Joint Decoupling Solver) is to decompose the fingertip space without inter-finger coupling and RIJDS(Resolved inter-Joint Decoupling Solver) is to decompose the compliance characteristic in the finger-tip space into the compliance characteristic given in the joint space without inter-joint coupling. Based on the analysis results the finger structure should be biominetic in the sense that either kniematic redundancy or force redundancy are required to implement the proposed compliance control scheme, Five-bar fingered robot hands are used as an illustrative example to implement the proposed compliance control method. To show the effectiveness of the proposed compliance control method simulations are performed for two-fingered and three-fingered robot hands.

• Journal of the Korean GEO-environmental Society
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• v.8 no.5
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• pp.23-29
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• 2007

The performance of the improved soil against liquefaction depends upon the chemical density, and it has been decided on the basis of the unconfined compressive strength of the improved soil up to date. On the other hand, several authors have proposed that the stiffness degradation could be treated as the clue for the judgment of the possibility of liquefaction. In this study, therefore, the stiffness degradation of the improved soil was estimated as the resistance against liquefaction by using the strain controlled cyclic triaxial test equipment. Based on the test results, it is concluded that the chemically treated sand can resist against the liquefaction in aspect of the reduction in effective stress and in the stiffness. Furthermore, even in the case of low chemical density, such as 2% in this study, has enough liquefaction resistance when compared with the 5~6% which often used in practical design. Considering this fact, the design of chemical density based on the unconfined strength can lead the overestimation in chemical density, and chemical density can be reduced when considering the stiffness reduction shown in this study.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.2
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• pp.620-626
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• 2016

Estimating the nonlinear seismic response of structure in earthquake engineering is important. Nonlinear static analysis is a typical method, and a variety of methods and techniques for estimating the stiffness of structural system at a certain analysis stage have been introduced and used in numerical structural analysis. On the other hand, such methods have many difficulties in practical usage because they use time-consuming iterative methods or simplified algorithms for calculating the structural stiffness at specific points in the time of nonlinear static analysis. For this reason, this study suggests an accurate and effective method for estimating the stiffness of a structure in nonlinear static analysis. For this goal, existing theories of an incremental step-by-step solution was investigated first. Subsequently, an algorithm available for calculating the precise stiffness of a structural system, each element of which has a bilinear material model, was developed based on the investigated methods. Finally, a computer program, sNs, was developed with the algorithm used.

• Journal of Biomedical Engineering Research
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• v.40 no.5
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• pp.158-164
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• 2019

The interbody fusion cage used to replace the degenerative intervertebral disc is largely composed of titanium-based biomaterials and biopolymer materials such as PEEK. Titanium is characterized by osseointergration and biocompatibility, but it is posed that the phenomenon such as subsidence can occur due to high elastic modulus versus bone. On the other hand, PEEK can control the elastic modulus in a similar to bone, but there is a problem that the osseointegration is limited. The purpose of this study was to implement titanium material's stiffness similar to that of bone by applying cellular structure, which is able to change the stiffness. For this purpose, the cellular structure A (BD, Body Diagonal Shape) and structure B (QP, Quadral Pod Shape) with porosity of 50%, 60%, 70% were proposed and the reinforcement structure was suggested for efficient strength reinforcement and the stiffness of each model was evaluated. As a result, the stiffness was reduced by 69~93% compared with Ti6Al4V ELI material, and the stiffness most similar to cortical bone is calculated with the deviation of about 12% in the BD model with 60% porosity. In this study, the interbody fusion cage made of Ti6Al4V ELI material with stiffness similar to cortical bone was implementing by applying cellular structure. Through this, it is considered that the limitation of the metal biomaterial by the high elastic modulus may be alleviated.

• Journal of the Korea Society of Computer and Information
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• v.28 no.10
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• pp.77-84
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• 2023

Simulating the cohesion and stiffness of wet hair or fur in physics-based simulations is one of the most challenging problems. Wet hair or fur is characterized by bunching and stiffening at the ends, a phenomenon that can be seen in wet animal fur or hair. In addition, when wet hair interacts with a solid, adhesion occurs, but this problem becomes difficult to solve due to the different distribution and balance of forces in curly hair. In traditional methods, wet hair is represented by hand or by using static hairstyles to represent wet curls and hair. However, how to depict the details of wet curly hair has not been actively researched. In this paper, we propose a new algorithm to efficiently model the curl exaggeration, cohesion, adhesion, and stiffness of wet curly hair. The proposed method efficiently simulates cohesion and integrates stiffness constraints with curl dynamics to reliably control hair elasticity.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.389-392
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• 2004

It is clinically well known that pre-tension of wires increases the fracture stability in ring or hybrid external fixation. In some cases, additional half pin should be necessary to increase the stability when soft tissue impalement occurs during fixation. In this paper, the fracture stability of a hybrid external fixator system with different pre-tension effects and additional half-pins was analysed using FEM to investigate the effects of these pre-tension and half pin on the system stability quantitatively. 3-D finite element models of five different fixator frames were developed using by beam elements. In axial compression analysis, the fracture stiffness was increased maximally 62％ as the pre-tension increased. In torsion analysis, in the other hand, there is little variations in the fracture stiffness. Additional half pin increased the system stiffness about 200 ％. From the results, proper pre-tension and additional half pin would provide good methods to increase the fracture stability of the hybrid external fixator and provide more surgical options to minimize soft tissue damage at the fracture site.

• Journal of the Korean Society of Physical Medicine
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• v.15 no.4
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• pp.29-35
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• 2020

PURPOSE: This study examined the immediate effects of Graston instrument-assisted soft-tissue mobilization (GIASTM) and self-stretching on the muscular properties of the gastrocnemius in athletes. METHODS: Thirty subjects (All in their 20 s) were distributed randomly and evenly into two groups of 15 each: GIASTM and stretching. The subjects had no history of gastrocnemius damage in the previous three months. The muscle tone, stiffness, elasticity, and mechanical stress relaxation time (MSRT) of the gastrocnemius were blind-tested. RESULTS: The GIASTM group showed significant changes in all categories, while only MSRT changed significantly in the self-stretching group after intervention. A comparison of the two groups revealed significant differences in stiffness, elasticity, and MSRT (Time required for the muscle to recover after distortion after intervention in the GIASTM group. CONCLUSION: In this study, significant decreases in muscle tone and stiffness, as well as significant increases in elasticity, were observed in the gastrocnemius of the GIASTM group. On the other hand, sSelf-stretching showed significant differences in MSRT. Therefore, GIASTM is more effective in the recovery of the gastrocnemius muscle from fatigue than self-stretching. This study suggests that GIASTM can help prevent damage to the gastrocnemius in athletes and contribute to their training and rehabilitation programs.

• Journal of the Korean Society of Clothing and Textiles
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• v.30 no.8
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• pp.1169-1177
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• 2006

The aim of this study was to investigate the change of the weight loss, tensile strength, flex stiffness, and color-values of the pigment-dyed cotton, polyester/cotton, polyester and nylon fabrics after washing process. Pigment-dyed cotton and polyester/cotton fabrics were treated with the cellulase, of which concentrations were 0, 1, 3 and 5g/l. The time of washing process ranges from 30 to 120 minutes. Pigment-dyed polyester and nylon fabrics were treated without enzyme, of which the washing temperature were 13, 30, $55^{\circ}C$ and the washing time ranges from 30 to 120 minutes. Also, they were tested in terms of the influences of agitation speed(rpm) and additives such as softeners, enzymes, detergents. The weight loss and tensile strength of the pigment-dyed cotton and polyester/cotton fabrics were positively correlated with the concentration of cellulase and washing time. Neither polyester nor nylon fabrics exhibited any change of the weight. All fabrics showed the decline of flex stiffness and decoloration after washing process. Decoloration of cotton and polyester/cotton fabrics was due to both the influence of cellulase and the mechanical rubbing. On the other hand, that of polyester and nylon fabrics was caused by the mechanical rubbing only.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.11
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• pp.1998-2003
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• 2007

A flexible but implantable polyimide-based neural implant was fabricated for reliable and stable long-term monitoring of neural activities from brain. The developed neural implant provides 3-dimensional (3D) $3{\times}3$ structure, avoids any hand handling, and makes the insertion more efficient and reliable. Any film curvature caused by residual stress was not observed in the electrode. The 3D flexible polyimide electrode penetrated a dense gel whose stiffness is close to live brain tissue, because a ${\sim}1{\mu}m$ thick nickel was electroplated along the edge of the shank in order to improve the stiffness. The recording sites were positioned at both side of the shank to increase the probability of recording neural signals from a target volume of tissue. Impedance remained stable over 72 hours because of extremely low moisture uptake in the polyimide dielectric layers. At electrical recording test in vitro, the fabricated electrode showed excellent recording performance, suggesting that this electrode has the potential for great recording from neuron firing and long-term implant performance.