• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.845-846
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• 2013

• Journal of the Korean Society for Precision Engineering
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• v.22 no.12 s.177
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• pp.190-197
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• 2005

For precise micro-grooving and surface machining, a mechanism for creating elliptical vibration cutting (EVC) motion is proposed which uses two parallel piezoelectric actuators. And based on its kinematical analysis, variations of EVC path are investigated as a function of dimensional changes in the mechanism, phase difference and amplitude of excitation sinusoidal voltages. Using the proposed PZT mechanism, various types of two dimensional EVC paths including one dimensional vibration cutting path along the cutting direction and thrust direction can be easily obtained by changing the phase lag, the amplitude of the piezoelectric actuators, and the dimension of the mechanism.

• Journal of Audiology & Otology
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• v.25 no.1
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• pp.43-48
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• 2021

Background and Objectives: Conflicting mechanisms have been reported about spontaneous reversal of positional nystagmus during head-roll maneuver in patients with benign paroxysmal positional vertigo (BPPV). The objective of this study is to review the reports about the characteristics and possible mechanisms of reversing positional nystagmus and to present seven new cases. Subjects and Methods: Seven cases (5 males, 2 females; 4 left-sided, 3 right-sided) were recruited among 732 patients with BPPV seen outpatient clinic between 2009 and 2019. Diagnosis of lateral canal canalolithiasis was confirmed when transient geotropic nystagmus was documented during head-roll test. Reversing positional nystagmus was analyzed in each case and clinical characteristics of the patients were documented. Results: The age of patients was ranging between 30 to 64 years (46.44±10.91). Duration of symptoms was short (21.34±19.74). Six of them had a story of head trauma. Initial latency was short. First, intense geotropic nystagmus was observed following provocative head-roll position on the affected side. There was short "silent phase". Then, a longer second-phase of reversed nystagmus was noted. Total duration of nystagmus was 78.40±6.82 seconds. Maximal slow phase velocity was 24.05±6.34 deg/sec. All patients were cured with barbeque maneuver. Conclusions: Ipsilateral reversing positional nystagmus during head-roll maneuver is due to lateral canal canalolithiasis. Mechanism is likely to be due to endolymphatic double flow. Bilateral cases may be due to simultaneous co-existence of canalolithiasis and cupulolithiasis. Longer recording of nystagmus is recommended not to miss the cases with spontaneous direction-changing positional nystagmus.

• Korean Journal of Audiology
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• v.25 no.1
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• pp.43-48
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• 2021

Background and Objectives: Conflicting mechanisms have been reported about spontaneous reversal of positional nystagmus during head-roll maneuver in patients with benign paroxysmal positional vertigo (BPPV). The objective of this study is to review the reports about the characteristics and possible mechanisms of reversing positional nystagmus and to present seven new cases. Subjects and Methods: Seven cases (5 males, 2 females; 4 left-sided, 3 right-sided) were recruited among 732 patients with BPPV seen outpatient clinic between 2009 and 2019. Diagnosis of lateral canal canalolithiasis was confirmed when transient geotropic nystagmus was documented during head-roll test. Reversing positional nystagmus was analyzed in each case and clinical characteristics of the patients were documented. Results: The age of patients was ranging between 30 to 64 years (46.44±10.91). Duration of symptoms was short (21.34±19.74). Six of them had a story of head trauma. Initial latency was short. First, intense geotropic nystagmus was observed following provocative head-roll position on the affected side. There was short "silent phase". Then, a longer second-phase of reversed nystagmus was noted. Total duration of nystagmus was 78.40±6.82 seconds. Maximal slow phase velocity was 24.05±6.34 deg/sec. All patients were cured with barbeque maneuver. Conclusions: Ipsilateral reversing positional nystagmus during head-roll maneuver is due to lateral canal canalolithiasis. Mechanism is likely to be due to endolymphatic double flow. Bilateral cases may be due to simultaneous co-existence of canalolithiasis and cupulolithiasis. Longer recording of nystagmus is recommended not to miss the cases with spontaneous direction-changing positional nystagmus.

• Journal of Information Technology Services
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• v.10 no.4
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• pp.259-268
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• 2011

A robot education system by emulation based on Web can be efficiently used for understanding concept of robot assembly practice and control mechanism of robot by control programming. It is important to predict the path of the line tracer robot which has to be decided by the robot. Shortest Path Algorithm is a well known algorithm which searches the most efficient path between the start node and the end node. There are two related typical algorithms. Dijkstra Algorithm searches the shortest path tree from a node to the rest of the other nodes. $A^*$ Algorithm searches the shortest paths among all nodes. The delay time caused by turning the direction of navigation for the line tracer robot at the crossroads can give big differences to the travel time of the robot. So we need an efficient path determine algorithm which can solve this problem. Thus, It is necessary to analyze the overhead of changing direction of robot at multi-linked node to determine the next direction for efficient routings. In this paper, we reflect the real delay time of directional changing from the real robot. A speed based Dijkstra algorithm is proposed and compared with the previous ones to analyze the performance.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.9
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• pp.1-12
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• 1996

In this paper, we propose an adaptive gait by which a quadruped walking robot can walk against external disturbances. This adaptive gait mechanism makes it possible for a quadruped walking robot to change its gait and accommodate external disturbances form various external environmental factors. Under the assumption that external disturbances can be converted to an external force acting on the body of a quadruped walking robot, we propose a new criterion for the stability margin of a waling robot by using an effective mass center based on the zero moment point under unknown external force. And for a solution of an adaptive gait against external disturbances, an method of altitude control and reflexive direction control is suggested. An algorithmic search method for an optimal stride of the quadruped mehtod, the gait stability margin of a quadruped walking robot is optimized in changing its direction at any instance for and after the reflexive direction control. To verify the efficiency of the proposed approach, some simulaton results are provided.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.1
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• pp.20-27
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• 2001

A variable configuration tracked vehicle(VCTV) is developed to reduce turning energy and improve climbing ability for stairs. This mechanism has four track T-type frames. By changing the driving direction, each track T-type frame rotates to minimize the contact area with ground. It also has better performance than other VCTV in energy consumption of turning. Futhermore this mechanism is more stable than other VCTV on the rough terrain. When climbing stairs, each track T-type frame rotates to obtain a front attack angle and keep stability on steep stairs. The design parameters of components of track T-type frames are optimized to enhance the performance of climbing stairs. Performance indices include a stable angle, a climbing ability, a height of the vertical obstacle. In case that the overall length of the mechanism is 0.2m, it is required that the radius of the wheels should be 5mm and the length track contacted with he ground should be 0.09m to climb higher and steeper stairs.

• Applied Science and Convergence Technology
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• v.27 no.4
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• pp.70-74
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• 2018

We fabricated an anode-type ion source driven by a charge repulsion mechanism and investigated its beam shape controlled by a Whenelt mask integrated at the front face of the source. The ion beam shape was observed to vary by changing the geometry of the Whenelt mask. As the angle of inclination of the Whenelt mask was varied from $40^{\circ}$ to $60^{\circ}$, the etched area at a thin film was reduced from 20 mm to 7.5 mm at the working distance of 286 mm, and the light transmittance through the etched surface was increased from 78% to 80%, respectively. In addition, for the step height difference, ${\Delta}$ between the inner mask and the outer mask of ${\Delta}=0$, -1 mm, and +1 mm, we observed the ion beam shape was formed to be collimated, diverged, and focused, respectively. The focal length of the focused beam was 269 mm. We approved experimentally a simple way of controlling the electric field of the ion beam by changing the geometry of the Whenelt mask such that the initial direction of the ion beam in the plasma region was manipulated effectively.

• Journal of computational fluids engineering
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• v.19 no.3
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• pp.69-76
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• 2014

The shock buffet on a transonic transport aircraft are negative factors that reduce the aerodynamic performance of aircraft. The parametric studies were performed for position of nacelle/pylon to estimate the trend of flow mechanism under the wing that affects shock buffet. To generate external mesh of aircraft configuration that change the position of nacelle, snappyHexMesh provided in OpenFOAM was applied. Implicit density-based solver(ISAAC) was used for flow analysis. The change of nacelle position along horizontal direction dynamically affected the aerodynamic performance of transonic transport aircraft as comparing that of vertical direction. As a result of the parametric study of nacelle/pylon position, it was confirmed that the optimal position of nacelle can be obtained by aerodynamic design.

• Journal of Digital Convergence
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• v.11 no.11
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• pp.753-766
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• 2013

Even though civilization is developing at a fast rate, human beings and their living environments do not look happy. Given that the civilization comes from the human mind, which is changing in interaction with human body, society, and nature, it is hard to think that the human mind is changing in the desirable direction. This paper described a whole changing paradigm of the human mind and its causes through the cognitive mechanism in the brain from which all the diverse minds are formed. According to the cognitive mechanism, the human mind can change from the first free and peaceful mind through the middle mind to the last obsessive and anguish mind in accordance with the change of one of the factors in the origin of the human mind. Today's unfavorable changes in human beings, society, and the natural environment including the excessive development of civilization are the results of the undesirable changes of the human mind. This paper specified the respective characteristics of the first, middle, and the last mind and discussed where individuals' minds are and where they are going. Lastly, this paper suggested the specific ways to return to the first original mind based on the cognitive mechanism.