• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.13 no.4
• /
• pp.247-257
• /
• 2003

This paper presents an analytical method to Investigate the stability of a hydrodynamic journal bearing with rotating herringbone grooves. The dynamic coefficients of the hydrodynamic Journal bearing are calculated using the FEM and the perturbation method. The linear equations of motion can be represented as a parametrically excited system because the dynamic coefficients have time-varying components due to the rotating grooves, even in the steady state. Their solution can be assumed as a Fourier series expansion so that the equations of motion can be rewritten as simultaneous algebraic equations with respect to the Fourier coefficients. Then, stability can be determined by solving Hill's infinite determinant of these algebraic equations. The validity of this research is proved by the comparison of the stability chart with the time response of the whirl radius obtained from the equations of motion. This research shows that the instability of the hydrodynamic journal bearing with rotating herringbone grooves increases with increasing eccentricity and with decreasing groove number, which play the major roles in increasing the average and variation of stiffness coefficients, respectively. It also shows that a high rotational speed is another source of instability by increasing the stiffness coefficients without changing the damping coefficients.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.05a
• /
• pp.166-174
• /
• 2002

This paper presents an analytical method to Investigate the stability of a hydrodynamic journal bearing with rotating herringbone grooves. The dynamic coefficients of the hydrodynamic journal bearing are calculated using the FEM and the perturbation method. The linear equations of motion can be represented as a parametrically excited system because the dynamic coefficients have time-varying components due to the rotating grooves, even in the steady state. Their solution can be assumed as a Fourier series expansion so that the equations of motion can be rewritten as simultaneous algebraic equations with respect to the Fourier coefficients. Then, stability can be determined by solving Hill's infinite determinant of these algebraic equations. The validity of this research is proved by the comparison of the stability chart with the time response of the whirl radius obtained from the equations of motion. This research shows that the instability of the hydrodynamic journal bearing with rotating herringbone grooves increases with increasing eccentricity and with decreasing groove number, which play the major roles in increasing the average and variation of stiffness coefficients, respectively. It also shows that a high rotational speed is another source of instability by increasing the stiffness coefficients without changing the damping coefficients.

• Journal of the Korean Society for Precision Engineering
• /
• v.27 no.7
• /
• pp.63-70
• /
• 2010

We developed a new punching system that generates pinholes expressing texts or images on a plastic plate. The pin-holed plate is used as a new glamorous display board reflecting colorful lights from the light emitting diode (LED) installed on the edge side of the plate. The four degree-of-freedom punching system was designed to make same multiple holes on four plastic plates simultaneously. For this motion, we designed a structure for a simultaneous motion of the system. For even reflection of the lights from texts or images on the board and fast production of the pin-holed boards, fast motion including precise position control is very important. We also built a PC-based integrated control system including a GUI program to help users easily design luminous texts or images on the plastic plate. Also, we conducted a performance test of the system to verify the punching speed and position control of the pin holes on the plate.

• Journal of Ocean Engineering and Technology
• /
• v.18 no.4 s.59
• /
• pp.1-7
• /
• 2004

A simultaneous measurement system that can analyze the flow-structure interaction has been developed. This system consists of four CCD cameras, two for capturing instantaneous flow fields and two for tracking a solid body. The three-dimensional vector fields around a cylinder are measured, while the motion of the cylinder forced by the flow field is measured, simultaneously, with the constructed system. The cylinder is suspended in the working fluid of a water channel, and the surface of the working fluid is forced sinusoidally to make the cylinder bounced. Reynolds number for the mean main stream is about 3500. The interaction between the flow fields and the cylinder motion is examined quantitatively.

• Journal of Acupuncture Research
• /
• v.31 no.2
• /
• pp.111-118
• /
• 2014

Objectives : Through an analysis of the previous studies, It is estimated that Chuna(shoulder traction) is effective in reducing the pain and increasing motion range of shoulder joint of the patient. So this study is to investigate the effects of Chuna(shoulder traction) on frozen shoulder. Methods : After treated with acupuncture and electro stimulating therapy, the subjects were measured list of measurement. And then treated with Chuna(shoulder traction) therapy, the subjects were measured list of measurement again. All treatment was performed by the same doctor who is a highly qualified about Chuna(shoulder traction). Chuna(shoulder traction) treatment takes 15 minutes. Three kind of Chuna(shoulder traction) therapy were performed for 5 minutes each. Depending on the degree of the subject's pain, treatment strength was adjusted. Results : - Chuna simultaneous treatment group, shoulder joint range of flexion, extension, abduction, adduction, external rotation and internal rotation movement improved statistically significant. - Chuna simultaneous and acupuncture treatment group, visual analogue scale(VAS) scores of two groups decreased statistically significant. Conclusions : The result suggests that Chuna(shoulder traction) can be effective to recover range of motion and reduce pain on patients with frozen shoulder.

• Journal of Ocean Engineering and Technology
• /
• v.23 no.2
• /
• pp.58-68
• /
• 2009

The increased use of unmanned underwater vehicles (UUV) has led to the development of alternative navigational methods that do not employ acoustic beacons and dead reckoning sensors. This paper describes a simultaneous localization and mapping (SLAM) scheme that uses range sonars mounted on a small UUV. A SLAM scheme is an alternative navigation method for measuring the environment through which the vehicle is passing and providing the relative position of the UUV. A technique for a SLAM algorithm that uses several ranging sonars is presented. This technique utilizes an unscented Kalman filter to estimate the locations of the UUV and surrounding objects. In order to work efficiently, the nearest neighbor standard filter is introduced as the data association algorithm in the SLAM for associating the stored targets returned by the sonar at each time step. The proposed SLAM algorithm was tested by experiments under various three degrees of freedom motion conditions. The results of these experiments showed that the proposed SLAM algorithm was capable of estimating the position of the UUV and the surrounding objects and demonstrated that the algorithm will perform well in various environments.

• Journal of the Korea Computer Graphics Society
• /
• v.18 no.3
• /
• pp.9-16
• /
• 2012

In this paper, we present a new method for reconstructing detailed facial expression from roughly captured data with a small number of markers. Because of the difference in the required capture resolution between the full-body capture and the facial expression capture, they hardly have been performed simultaneously. However, for generating natural animation, a simultaneous capture for body and face is essential. For this purpose, we provide a method for capturing the detailed facial expression only with a small number of markers. Our basic idea is to build a database for the facial expressions and apply the principal component analysis for reducing the dimensionality. The dimensionality reduction enables us to estimate the full data from a part of the data. We justify our method by applying it to dynamic scenes to show the viability of the method.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.17 no.6
• /
• pp.217-222
• /
• 2017

Any object located in the earth's gravitational field experiences a force in the direction of the center of the earth. In order to describe the motion of objects in the field, the solutions to a system of simultaneous vector kinematic equations need to be obtained. In the analysis of freely-falling objects, the reference direction +y is usually defined to be the downward direction. In the analysis of the motion of objects thrown upward, the reference direction +y is usually defined to be the upward direction. In the analysis of the motion of objects thrown downward, the reference direction +y is usually defined to be the downward direction. In this paper, we show that the choice of reference axis in either upward or direction gives the same results by adopting a scalar product of two vectors in solving the vector kinematic equations. It is rare to find other examples of using a scalar product of two vectors in solving vector kinematic equations describing the motion of objects. An application of this study is that we can arbitrarily choose the reference direction for objects moving in a horizontal direction, including projectile motions.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.21 no.10
• /
• pp.1683-1693
• /
• 1997

In this paper, a new nonlinear dynamic model is derived for a 2-dimensional overhead crane based on a new definition of 2-degree-of-freedom swing angle, and a new anti-swing control law is proposed for the crane. The dynamic model and control law take simultaneous travel and traverse motions of the crane into consideration. The model is first linearized for small motions of the crane load about the vertical stable equilibrium. Then the model becomes decoupled and symmetric with respect to the travel and traverse axes of the crane. From this result, a decoupled anti-swing control law is proposed based on the linearized model via the loop shaping and root locus methods. This decoupled method guarantees not only fast damping of load-swing but also zero steady state position error with optimal transient response for the 2-dimensional motion of the crane. Finally, the proposed control method is evaluated by controlling the simultaneous travel and traverse motions of a 2-dimensional prototype overhead crane. The effectiveness of the proposed control method is then proven by the experimental results.

• Journal of Haehwa Medicine
• /
• v.25 no.1
• /
• pp.15-26
• /
• 2016

Objectives : The aim of this study was to report the cases of knee injury that are treated with both CPM and Korean medicine. Methods : We treated 3 patients who had knee joint pain and gait disturbance by knee injuries with Korean medicine and CPM treatment. We evaluated the outcomes by checking NRS, ROM, Lysholm knee score, walking state and other symptoms. Results : The NRS, ROM, Lysholm knee score, and other symptoms of 3 patients were improved before they. These results show possibilities of simultaneous treatment of Korean medicine and CPM. But there is a limit that the number of cases is not sufficient, and there was no long-term follow-up after discharge. Conclusions : Simultaneous treatment of Korean medicine and CPM has an effect on knee joint rehabilitation. Further studies are needed to prove the effectiveness of Korean medicine combined with CPM.