• The Journal of Korean Academy of Prosthodontics
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• v.43 no.5
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• pp.671-683
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• 2005

Statement of problem: The most commonly reported problem associated with dental implant restoration is the loosening of the screws. Purpose: This study compared the efficacy of an implant system incorporating an anti-rotational locking sleeve(Anti-Rotating Inner Post Screw System(ARIPS-system)) with other, traditional implant systems as a means of minimizing vibration loosening. Materials and methods: Three implant systems were examined; the conventional external hex type, the ARIPS-system, and the internal taper type implant system 30 specimens(10 samples per group)were fabricated and each abutment screw was secured to the implant future with 32Ncm of torque force and loosening torque was measured using a Torque Gauge. The procedure was repeated 3 times, recording initial loosening torque each time. The re-tightened abutment screw was subjected to a cyclic load having a maximum forte of 200N and minimum of 20N at 2Hz over a period of 12,600 cycles. after which the loosening torque was measured. Measured values were calaulated for statistical analysis. Analysis of measured value was performed by 3 methods: (i) as a percentage average of the initial 3 loosening-torque values(initial loosening value) to the tightening torque of 32Ncm, (ii) as a percentage of the loosening torque value after a load of 200N(experimental value) to the initial loosening value, and (iii) as a percentage of the experimental value to the 32Ncm of tightening torque. The analyses shows the amount of initial loosening at the screw, loosening by repetitive load and the the final loosening value. Results: The results of this study were as follows (1) Percentage of initial loosening value to tightening-torque was increased in order of external hex, ARIPS-system and internal taper and all values between each groups showed statistical significance (p<0.05). (2) Percentage of experimental value to initial loosening value was increased in order of external hex, ARIPS-system and internal taper. Value of internal taper showed significant difference with those of external hex and ARIPS-system (p<0.05). (3) Percentage of experimental value to tightening torque was increased in order of external hex, ARIPS-system and internal taper and all values between each groups showed statistical significance (p<0.05). Conclusion: The results of the analysis of the final loosening level value, which are closely correlated to clinical use, show that the ARIPS-system can be a useful means of minimizing abutment screw loosening when compared to the external hex type system. Although further clinical studies need to be made, the ARIPS-system should be considered to maximize the long-term success of the implant prosthesis.

• Journal of Technologic Dentistry
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• v.35 no.3
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• pp.201-207
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• 2013

Purpose: In this study, the loosening torque test was conducted with three implant products that are produced, approved and sold in Korea, which are manufactured in different fixture and abutment tightening methods (internal submerged type, internal morse taper type, and external type) to examine the loosening torque of the screw according to the method of tightening the implant fixture and abutment. Methods: In the loosening torque test, the three types of fixtures and abutments with different tightening methods were tightened by rotating them clockwise with a $30N{\cdot}cm$ force using a driver equipped with an electric torque meter. The results of the test are as follows. Results: The loosening torque values of the internal submerged type, internal morse taper type and external type implants were $24.10{\pm}0.742N{\cdot}cm$, $29.10{\pm}1.710N{\cdot}cm$, and $26.60{\times}1.636N{\cdot}cm$, respectively. Conclusion: The screw loosening torque values of the three fixture and abutment tightening methods were analyzed via Kruskal Wallis test layout, and they were significantly different (p<0.05).

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.9
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• pp.882-887
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• 2011

A spiral electrodynamic wheel is proposed as an actuator for the contactless conveyance of a conductive rod. When rotating the wheel around the rod, a radial force, a tangential force, and an axial force are generated on the rod and cause a screw motion of the rod. The rotation of the rod is the inevitable result due to traction torque of the wheel and the unintended motion to be excluded. However, the rotating speed of the rod should be measured without mechanical contact to be cancelled out through the controller, so the electrodynamic wheel is used as a sensor measuring the rotating speed of the rod indirectly as well as an actuator. In this paper, we model the magnetic forces by the proposed wheel theoretically and compare the derived model with simulation result by Maxwell, and analyze influences on the magnetic forces by key parameters constituting the wheel. The feasibility of the conveyance system is verified experimentally.

• 전기의세계
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• v.23 no.2
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• pp.39-45
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• 1974

An analysis is developed for the torque characteristics of single-phase induction motors having variable shaded-pole angles. The machanism have two sets of stator windings which one set of stator fed from single-phase sources and other shorted by inserted external impedances. Thus, by phisically rotating one set of stator windings with respect to the other, the only shaded-kpole effect torque performance of a single- phase induction machine and its performance prediction to be expected of the optimum shaded-pole angle can be achieved.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.840-846
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• 2007

This paper investigates the dynamic behavior of a HDD spindle system due to the imperfect roundness of a rotating shaft. The shaft of a spindle motor rotates with eccentricity by the unbalanced mass of the rotating part. The eccentricity generates the run-out of a spindle motor which results in the eccentric motion of a rotating part. Roundness of a shaft affects this motion which limits the memory capacity of a HDD. This research proposes a modified Reynolds equation for the coupled journal and thrust FDBs to include the variable film thickness due to the roundness. Finite element method is used to solve the Reynolds equation for the pressure distribution. Reaction forces and friction torque are obtained by integrating the pressure and shear stress, respectively. The dynamic behavior is determined by solving the equations of a motion of a HDD spindle system in six degrees of freedom with the Runge-Kutta method to characterize the motion of a rotating part. This research shows that the roundness of a rotating shaft causes the excitation frequency with integer multiple of a rotating frequency.

• Journal of Auto-vehicle Safety Association
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• v.16 no.2
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• pp.51-59
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• 2024

This study presents a method for health monitoring of rotating objects for mobility based on multiple recursive least squares(RLS) algorithms. The performance degradation of the rotating objects causes low handing / low driving performances and even fatal accidents. Therefore, health monitoring algorithm of rotating objects is one of the important technologies for mobility fail-safe and maintenance areas. In order for health monitoring of rotating objects, four recursive least squares algorithms with forgetting factor were designed in this study. The health monitoring algorithm proposed in this study consists of two steps such as uncertainty estimation and parameter changes estimation. In order to improve estimation accuracy, time delay function was applied to the estimated signals based on the first order differential equation and forgetting factors used for the RLS were reasonably tuned. The health monitoring algorithm was constructed in Matlab/Simulink environment and simulation-based performance evaluation was conducted using DC motor model. The evaluation results showed that the proposed algorithm estimates the actual parameter differences reasonably using velocity and current information.

• Journal of KSNVE
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• v.5 no.4
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• pp.565-575
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• 1995

Gearboxes are often used in the petrochemical and electrical power plants to transmit mechanical power between two branches of a machinery train rotating at different speeds. When the gearboxes are connected with rotors supported by journal bearings, bearing loads vary in magnitude and direction with rotor speed and torque transmitted by the gearboxes. In this study, dynamic characteristics of the system which consists of gearboxes and a rotor supported by journal bearings are investigated analytically and experimentally by employing the polynomial transfer matrix method and modal analysis under different speeds and torque levels. Journal bearing loads due to the transmitted torque are claculated analytically and the stiffness and damping coefficient of the journal bearings are obtained using finite element method. Comparison of the analytical and experimental results shows that the cross coupled stiffness coefficients increase with increasing rotor speed, while the cross coupled damping coefficients decrease. This generates the oil whirl instability in the journal bearings. As the transmitted torque level goes up, the stiffness coefficients of the journal bearing and the first horizontal natural frequency increase. High levels of the transmitted torque produce high bearing stiffness since the contact loads of the mating gear teeth increase. The logarithmic decrement, which is a stability indicator, is shown to decrease with increasing speed and decreasing torque. Thus, at the low torque level, the system become unstable even at the low shaft speed.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.814-815
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• 2011

A surfaced permanent magnet spherical motor is capable of operating as three degree of freedom that used for the joints of the robot's arm, leg, and eyes. Ongoing research like new concept is essential part of motor field, it will make a great contribution in the future the overall portion of the motor, is becoming expected. The author analysis torque characteristics in spherical motor with state of rotating and positioning. And future design direction is smaller motors with equivalent or higher output. Solutions as torque and efficiency improvements are selecting the core with special processing type like powder metallurgy materials. Their special characteristic is high permeability and low eddy current losses at high speed, so improved the torque and efficiency.

• Journal of the Korean Magnetics Society
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• v.1 no.2
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• pp.89-93
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• 1991

A new kind of a non-contact torque sensor which uses the difference of the maximum magnetic inductions as measurand was constructed. The torque sensor utilizes the tensile and compressive stress of two cores which are attached on the rotating shaft. This sensor shows that the linearity was better than 1 %, and the transient torque can be measured at the sampling rate of 10 kHz which is the same as magnetizing frequency of the core.

• Proceedings of the KIEE Conference
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• 2002.04a
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• pp.46-48
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• 2002

It needs to study on proper brake performance used in servo system of industrial application. In this study, braking torque of eddy current brake between electromagnet stator and rotating disk are analyzed. The torque-speed characteristics and proper disk construction are presented in this paper. From the computer simulation results, it was found that eddy current braking torque is linear or approximately constant over the desired speed range depending on the rotor material, disk construction, pole number and pole displacement of stator.