• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.201.2-201.2
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• 2016

$Mg_xNi_yZn_{1-x-y}Fe_2O_4$ ferrite powders were prepared by self-propagating high temperature synthesis followed by classified by ultrasonic wet-magnetic separation method to get nano-sized particles with high purity. The $Mg_xNi_yZn_{1-x-y}Fe_2O_4$ ferrites were well formed by using several powders like iron, nickel oxide, zinc oxide and magnesium oxide at 0.1 MPa of oxygen pressure. The ultrasonic wet-magnetic separation of pre-mechanical milled ferrite powders produced the powders with average size of $3.7-0.8{\mu}m$. The addition of a surfactant during the separation process improved productivity more than twice. The coercive force, maximum magnetization and residual magnetization of the $Mg_xNi_yZn_{1-x-y}Fe_2O_4$ nano-powders with 810 nm size were 45.89 Oe, 53.92 emu/gOe, 0.4 emu/Oe, respectively.

• 제어로봇시스템학회논문지
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• 제9권8호
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• pp.585-591
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• 2003

A virtual force is generated and fed back to the operator to make the teleoperation more reliable, which reflects the relationship between a slave robot and an uncertain remote environment as a form of an impedance. In general, for the teleoperation, the teleoperated mobile robot takes pictures of the remote environment and sends the visual information back to the operator over the Internet. Because of the limitations of communication bandwidth and narrow view-angles of camera, it is not possible to watch certain regions, for examples, the shadow and curved areas. To overcome this problem, a virtual force is generated according to both the distance between the obstacle and the robot and the approaching velocity of the obstacle w.r.t the collision vector based on the ultrasonic sensor data. This virtual force is transferred back to the master (two degrees of freedom joystick) over the Internet to enable a human operator to estimate the position of obstacle at the remote site. By holding this master, in spite of limited visual information, the operator can feel the spatial sense against the remote environment. It is demonstrated by experiments that this collision vector based haptic reflection improves the performance of teleoperated mobile robot significantly.

• Journal of Electrical Engineering and Technology
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• 제8권6호
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• pp.1415-1423
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• 2013

The traveling wave ultra-sonic motor (TWUSM) is operated through the frictional force between the rotor and the stator. Hence, the contact mechanism should be analyzed to estimate the motor performance. However, the nonlinearity of the contact mechanism of the TWUSM makes it difficult to propose a proper contact model and a characteristic analysis method. To address these problems, a novel contact model is proposed and be termed the cylindrical dynamic contact model (CDCM) in this research. An estimation method of the motor performance is proposed using the CDCM, an analytical method, and a numerical method. The feasibility and usefulness of the proposed characteristic analysis are verified through experimental data.

• 동력기계공학회지
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• 제14권2호
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• pp.65-70
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• 2010

Retaining rings are used to support the field winding end turns from the centrifugal force by the high speed of the field and these are the overstressed parts among the generator parts. There have been several retaining failures in Europe and America, all attributable to stress corrosion cracking in 18Mn-5Cr steel. Since then, each manufacture companies have developed a good 18Mn-5Cr steel in temperature, strength characteristic and it is used in many field now. From many findings and test results, we could conformed that the failure might be grown in the overstressed condition unrelated to the moisture particle.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 F
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• pp.2151-2155
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• 1998

The traveling wave type ultrasonic motor(USM) has no electro-magnetic circuits( coil or core). The driving principle of the USM is based on high-frequency mechanical vibrations and frictional force. The USM, thus, is fed by two-phase high - frequency sinusoidal inverter using its series resonant parasitic components. For the using of series resonant type inverter, it should be needed to a USM parasitic capacitance and a proper inductor chosen. In this paper, the values of optimal inductance are designed and the efficiency of USM drives is achieved. The effectiveness of the proposed design is demonstrated by experiments.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.328-330
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• 1994

The Ultrasonic motor(USM) has many good characteristics such as high torque at low speed range, large holding torque based upon frictional force, high speed response, flexible free ferns, compactness in size, low magnetic noise and silentness in motion. Because of having low speed rotation, USM is good as an actuator of a small size direct drive (DD) manipulator. The acturators for the DD manipulators must have good controllability on the speed and torque from zero to maximum value continuously. New method was developed for speed and torque control by the phase difference control of the two-phase driving signals of the motor. Then rule adjustable compliant and dumped motion was realized on the output shaft of the motor by PD control of the output shaft angle.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1994년도 춘계학술대회 논문집
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• pp.21-24
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• 1994

A piezoelectric actuator. which is composed of a piezoelectrically driven stator and a rotor, Is made and the characteristics are investigated experimentally is a new ultrasonic actuator which transforms rotary motion to linear one is proposed and proved to work successfully. If an ultrasonic wave is excited to propagate in the stator, particles on the internal surface move elliptically. Since the internal surface is machined as an internal thread and an external thread(rotor) is put into the stator. the external thread is rotated through the friction force and moved in the axial direction. The traveling wave is excited by a piezoelectric element bonded to the stator. This idea is firstly proposed by S. Ueha, et al. in 1987. However, efficiency of their actuator is less than 3%. In this study, in order to improve characteristics of this type actuator, we used various pitches and number of the screw thread, and materials of rotor, and we obtained good charcteristics.

• 공업화학
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• 제24권2호
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• pp.165-170
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• 2013

초고온가스로 핵연료 구형 UCO (uranium oxycarbide) 입자 제조과정 중 중간화합물 제조에서 적용하고 있는 내부겔화공정을 대체하기 위해 외부겔화공정을 도입하는 연구가 진행 중에 있다. 외부겔화공정을 이용해서 구형 UCO입자를 제조하기 위한 사전실험으로, 중간화합물인 ADU (ammonium di-uranate) 겔 입자를 제조하기 위한 원료용액인 모사 broth 용액을 제조하여 카본블랙 입자를 분산시키는 실험이 수행되었다. 다양한 종류의 카본블랙 입자를 사용해서 모사 broth 용액에 분산실험을 수행한 결과, Cabot G 제품이 용액상에서 분산안정성과 균일한 분산상태를 나타내고 있어서, 본 연구의 카본블랙으로 선정되었다. 또한 나노크기 입자로 응집된 카본블랙 입자를 고점성 액상물질에 효율적으로 분산시키기 위해서는, 금속염용액에 카본블랙 입자를 투입하고 ultrasonic force를 이용해서 응집입자를 해체한 다음, 고점성 물질인 PVA (poly vinyl alcohol)를 투입하여 강력한 기계식혼합기를 이용해서 6000 rpm으로 2차 분산 혼합시키는 경우, ultrasonic force에 의한 broth 용액의 물성이 유지되면서 카본블랙 입자의 분산안정성과 분산상태가 양호한 broth용액을 얻을 수 있었다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권9호
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• pp.427-433
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• 2001

A linear ultrasonic motor was designed by a combination of the first longitudinal and fourth bending mode, and the motor consisted of a straight aluminum alloys bar bonded with a piezoelectric ceramic element as a driving element. That is,$L_1-B_4$ linear ultrasonic motor can be constructed by a multi-mode vibrator of longitudinal and bending modes. Linear ultrasonic motors are based on an elliptical motion on the surface elastic body, such as bar or plates. In general, the natural resonance frequency of the stator is used as a driving frequency of the motor which provides a large elliptical motion. The corresponding eigenmode of one resonance frequency can be excited twice at the same time with a Phase shift of 90 degrees in space and time. And the rotation can be reversed by changing the phase between the two signals from sin$\omega$t to cos$\omega$t. Moreover, the tangential force pushes the slider(rotor) and, therefore, determines the thrust and speed of the motor. The experimental results of fabrication motors, bimorph-tyPe motor showed more excellent than unimorph-type. The maximum speed of TBL-200, TBL-300, TBL-400, TBL -220, TBL-310 and TBL-420 motors were 0.12, 0.37, 0.39, 0.14, 0.55 and $0.60ms6{-1}$, respectively. And the efficiency were reported 1.15, 7.9, 6.6, 2.36, 10.1 and 16.5%, respectively. That time, output thrust of the motor was a strong(1~2N) and the weight of stator was a lightness(5~7g).

• 대한중풍순환신경학회지
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• 제14권1호
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• pp.102-106
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• 2013

■ Objectives The purpose of the this study was to investigate organization change(pennation angle) of lower extremity muscle in elderly with knee osteoarthritis through ultrasonic image. Also, we examined organizational change of muscle was by influenced after total knee replacement(TKR). ■ Methods Rectus femoris image was taken at 50% of the distance between the anterior superior iliac spine and the superior border of the patella. Vastus medialis image was taken at the most distal insertion level of vastus medialis on the medial border of the patella. measurements included the most distal insertion level of the vastus medialis on the medial border of the patella. ■ Results Change of pennation angle in rectus femoris showed decrease from 5.11° in preoperation to 4.29° in 1 week after operation. Change of pennation angle in vastus medialis showed decrease from 6.94° in preoperation to 5.76° in 1 week after operation. ■ Conclusion We consider decrease of pennation angle after total knee replacement in this study was casued by organizational change of muscle and this pennation angle was influenced force created by muscle. Therefore, we thinks that this pennation angle through ultrasonic image will be available to plane individual muscle exercise program and to confirm muscle mass by muscle strength training.