• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1575-1579
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• 2008

The purpose of this study was to investigate how maximum-effort eccentric exercise over different contraction ranges affects the characteristics of torque-angle relationship of human ankle plantarflexor in-vivo. Subjects were randomly assigned in two groups. One group (n=6) performed 120 maximum-effort eccentric ankle dorsiflexion contractions at short muscle length (ankle range of motion from -5 to 15 deg) and the other group (n=6) at long (ankle range of motion from 10 to 30 deg) muscle length. Eccentric exercise decreased the maximum isometric ankle plantarflexion torque ${\sim}40%$. It was found that the optimum ankle joint angle changed from 7.5 deg to 11.1 deg and 10.1 deg, shifted toward the longer muscle length, regardless of the exercise range. The results of this study suggest that eccentric exercise alters the characteristics of torqueangle relationship of the muscle but there is no differential effect of the eccentric contraction range.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.133-139
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• 2007

In this paper, optics polishing technology using adaptive tool and eccentric motion mechanism was suggested. Optics polishing can make high reflective and accurate surface. The optics polishing process based on the eccentric motion mechanism has been used to manufacture the ophthalmic lens mold. Also ophthalmic lens mold factory hold conventionally a lot of the curved polishing tools for the versatile mold curves of eye diopters and want to reduce tool numbers. Therefore, a polishing machine with adaptive airbag tool was developed and experimentally verified in view of surface roughness and form accuracy.

• The Journal of Korean Physical Therapy
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• v.14 no.4
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• pp.260-265
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• 2002

There are many methods for muscle strengthening. Muscle strengthening with eccentric contraction work is the best way by researcher's report. Also, eccentric contraction need proper resistance for muscle strengthening. Combination of isotonic in PNF is a muscle strengthening method with manual resistance. It makes concentric contraction $\rightarrow$ eccentric contraction $\rightarrow$ concentric contraction with continually and without muscle relaxation. Combination isotonic technique use with PNF pattern. Therefore, it will make development and increasing of active control motion, coordination, actual range of motion, strengthen and functional training in eccentric control of movement. Concentric contraction have the 3rd lever system and eccentric contraction have the 2nd lever system with combination of isotonic. Serial concentric contraction $\rightarrow$ eccentric contraction $\rightarrow$ concentric contraction make strong SEC and PEC. It will be increase elasticity of SEC, PEC and contractile components either.

• PNF and Movement
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• v.2 no.1
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• pp.25-33
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• 2004

Purpose : The purpose of this article is to summarize the characteristics of isotonic combination. Method : Some studies of the motor unit activation patterns during isometric, concentric, and eccentric actions, neural strategies in the control of muscle force, and concentric versus combined concentric-eccentric training were reviewed. Results & Conclusions : Eccentric torque may be relatively higher than concentric torque for two potential reasons: 1) stretch responses in the antagonist are not elicited to restrain the motion as can occur concentrically and 2) stretch responses in the agonist may augment eccentric torque production. Concentric-eccentric training has a greater influence on functional capacity than that of concentric training. Both maximal force and average force throughout the motion were significantly higher when the dynamic action was started with preactivation as compared to the mode without preactivation. The peak torques observed during the concentric phase of the eccentric-concentric muscle actions were higher than those noted in the pure concentric contraction.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.10
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• pp.897-904
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• 2011

When whole-body is exposed to vertical vibration, asymmetry shape of human body affects the response on the translational(fore-aft, lateral, vertical) and rotational(roll, pitch, yaw) motion. While the translational motion has been studied with various titles, it has been rare to study the rotational motion of human body exposed to vertical excitation because of lack of experimental equipment. This study was performed by using a 6-axis force plate installing strain gage type sensors for the rotational response. Sixteen male subjects were exposed to vertical vibration on rigid seat in order to investigate apparent mass of three translational motion and apparent eccentric mass of three rotational motion. Random signal was generated to make excitation vibration which was on an effective frequency range of 3~40 Hz, and magnitude of 0.224 m/$s^2$ r.m.s. The frequency range and magnitude used was selected for the vibration of passenger vehicle on idling condition. As the result, cross-axis apparent masses of fore-and-aft and lateral direction were not significant showing 20 % and 3 % of vertical apparent mass relatively. And apparent eccentric mass of pitch motion was dominant when compared to that of roll and yaw motion, which is reasoned by asymmetry direction of human body sitting on a seat.

• Transactions of Materials Processing
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• v.18 no.2
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• pp.172-176
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• 2009

In this paper, new aspherical surface polishing mechanism is suggested to polish aspherical glass lens mold by both airbag polishing tool and reverse-rotational eccentric motion. Up to now, conventional aspherical lens polishing method by the small tool polishing uses the aspherical surface profile and the trajectory of the polishing tool is also controlled. However, full contact concept by airbag polishing tool and no position control make the easy polishing setup and does not need aspherical design profile. An aspherical lens polishing machine was made for this study and a tool mark removal experiment fur the fine-grounded lens mold was successfully performed.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.3
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• pp.95-100
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• 2002

Built-in Eccentric Bearing-Torsional Spring (BEBTS) type Automatic Belt Tension Unit (ABTU) is one of typical belt tension units. The BEBTS type ABTU system frequently experiences torsional vibration about its pivot due to the variation of belt tension. However, it is very difficult to analyze the rotational (or torsional) vibration of the ABTU because the exciting moment varies according to the change of belt tension. To get over this difficulty, in this paper. the ABTU was simplified as 1-DOF translational motion model in the tangential direction. Its equation of motion was derived and solved. The time history and frequency responses were computed and examined for three of BEBTS type ABTUs which are made by different manufacturers but the tame kind.

• Structural Engineering and Mechanics
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• v.47 no.4
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• pp.455-470
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• 2013

This paper presents a theory concerning the beam element subjected to an eccentric rolling disk (or simply called the eccentric-disk-loaded beam element) such that the dynamic responses of a beam subjected to an eccentric rolling disk with its inertia force, Coriolis force and centrifugal force considered can be easily determined. To this end, the property matrices of an eccentric-disk-loaded beam element are firstly derived by means of the Lagrange's equations. Then, the overall property matrices of the entire vibrating system are determined by directly adding the property matrices of the eccentric-disk-loaded beam element to the overall ones of the entire beam itself. Finally, the Newmark direct integration method is used to solve the equations of motion for the dynamic responses of a beam subjected to an eccentric rolling disk. Some factors relating to the title problem, such as the eccentricity, radius and rotating speed of the rolling disk, and the Coriolis force and centrifugal force induced by the rolling disk are investigated. Numerical results reveal that the influence of last factors on the dynamic responses of the pinned-pinned beam is significant except the centrifugal force.

• Korean Journal of Applied Biomechanics
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• v.15 no.2
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• pp.155-165
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• 2005

The purpose of this study was to compare the muscle activities of Double Legged Jump (DLJ) and Single Legged Jump (SLJ) by the normalization of muscle activity. Eight college students without the lower extremity injuries were selected as subjects for collecting EMG data of vastus medialis and gastrocnemius. The entire section of motion was established as eccentric and concentric contractions, and each of the contractions was divided into three sections with equal timing intervals, which becomes a total of 6 phases. The EMG data of each phase was integrated and normalized. The muscle activities of the vastus medialis for both eccentric and concentric contractions were significantly different between DLJ and SLJ(p<.05). The increase in overall muscle activity of SLJ was 33.6%. Approximately, there was an increase of 25.9% in eccentric contraction and 40% in concentric contraction. Moreover, the data of the muscle activity of gastrocnemius was similar to the data of the muscle activity of vastus medialis. In conclusion, this research suggests muscle activity of a certain motion can be normalized for an analysis of another motion.

• Journal of Biosystems Engineering
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• v.43 no.3
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• pp.194-201
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• 2018

Purpose: The objective of this study was to propose a formula for the theoretical grain mean transport velocities of an elliptically moving oscillator by modifying the grain mean transport velocity formula applied to linear motion and to compare the calculated values with the experimental values of grain mean transport velocity. Methods: The values of the throwing index ($K_v$) and the maximum horizontal velocities for various positions on the elliptical oscillator were obtained using kinematic analysis. To obtain the actual grain transport velocity, the mean transport velocities of perilla grains at six positions on the sieve surface were measured using a high-speed camera and compared with the theoretical values. The cam with an eccentric bearing on the oscillator was designed to be eccentric by 1.6 cm so that the lengths of the major axis of the elliptical motion were 3.2-3.6 cm. The material used in the experiments was perilla grain. Results: The experimental result was consistent with the theoretical value calculated using the proposed formula ($R^2$ is 0.80). It is considered that the angle difference between the maximum accelerations in the directions vertical and horizontal to the sieve has as much influence on the grain mean transport velocity as the value of Kv itself. Conclusions: It was possible to theoretically obtain the grain mean transport velocities through a screening device in elliptical motion by modifying the formula of the grain mean transport velocities used in linear motion.