• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.9
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• pp.869-874
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• 2010

Recently, a piezo actuator based linear motor has been actively studied because of its higher power density, compactness and quick response. However, the characteristic of small displacement makes the application of a piezo actuator limitative. In order to overcome this limitation, some actuation mechanisms using a piezo actuator are designed by bi-metal composite or more than two piezo actuators. Therefore, it enables to generate large displacement and have high resolution. In the proposed piezo motor, we have designed a bi-directional linear motor that can be operated by only one piezo actuator. In addition, it is activated with low frequency of the applied voltage, since, we utilize first mode shape of structure of motion generator to vibrate. Finally, moving direction can be simply controlled by changing the ratio of input frequency to natural frequency of structure of motion generator.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.654-658
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• 2003

In this study a control system with variable gain schedule using real speed and moving direction is proposed to control a Permanent Magnet Linear Synchronous Motor (PMLSM) with Z-axis operation structure. The implementation of the controller is designed on the DSP TMS320C32 board. PMLSM is operated by using 4-point absolute positions profile with each velocity, acceleration and deceleration. The direction of the initial angle action for starting is set from the lower limit point to the upper limit point on PMLSM operation stroke. The effectiveness of a control system with variable gain schedule is demonstrated by some experimental results.

• Journal of Mechanical Science and Technology
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• v.17 no.3
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• pp.400-408
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• 2003

A study on the progressive inelastic deformation behavior of the 316 L stainless steel cylindrical structure with plate-to-shell junction under moving temperature front was carried out by structural test and analysis. The structural test intends to simulate the thermal ratcheting behavior occurring at the reactor baffle of the liquid metal reactor as free surface of hot sodium pool moves up and down under plant transients. The thermal ratchet load that heats the specimen up to 550$^{\circ}C$ was applied repeatedly and residual deformation was measured. The thermal ratcheting test was carried out with two types of cylindrical structures, one with plate to-shell junction and the other without the junction to investigate the effects of the geometric discontinuities on the global ratcheting deformation. The temperature distributions of the test specimens were measured and were used for the ratcheting analysis. The ratchet deformations were analyzed with the constitutive equation of the non-linear combined hardening model. The analysis results were in good agreement with those of the structural tests.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.484-487
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• 2006

In this paper, linear ultrasonic actuators are designed using two dimensional motions of a PMW-PT piezoelectric plate. By equalizing the natural frequencies of longitudinal and transverse vibration modes in the cantilever structure, the ultrasonic motion of the combined vibration modes are generated. We have designed two different PMN-PT actuators: one uses a tip attached on the edge of the actuator and it drives the object in the perpendicular direction of the tip. In other model, the actuator plate moves itself through stationary guides. Prototypes of the two models are manufactured and experiments results are compared to the theoretical and numerical results. The effects of structural characteristics and the friction force existing between the actuator tip and the moving object are considered. Experiments show the possibility of small size ultrasonic linear motors which can be applicable to small form factor information storage and phone camera actuators.

• Proceedings of the Korea Society for Simulation Conference
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• 1998.03a
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• pp.11-16
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• 1998

The classical algorithm for solving liner network flow problems are primal cost improvement method, including simplex method, which iteratively improve the primal cost by moving flow around simple cycles, which iteratively improve the dual cost by changing the prices of a subset of nodes by equal amounts. Typical iteration/shortest path algorithm is used to improve flow problem of liner network structure. In this paper we stdudied about the implemental method of shortest path which is a practical computational aspects. This method can minimize the best neighbor node and also implement the typical iteration which is $\varepsilon$-CS satisfaction using the auction algorithm of linear network flow problem

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.121-123
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• 2006

In this paper, the notch of teeth and skew of permanent magnet are used to reduce the detent force caused by slot-teeth structure. Also, the shape of permanent magnet is optimized to reduce the detent forceowing to flux hannonics components of permanent magnet. As a result, thrust is decrease about 2[%]. But, the distortion ratio of thrust is decreased from 1.04[%] to 0.75[%]. And, the ripple ratio of thrust is decreased from 2.6[%] to 1.65[%].

• Proceedings of the KIEE Conference
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• 2004.04a
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• pp.40-42
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• 2004

In this paper, optimum shape design of permanent magnet in slotted type Permanent Magnet Linear Synchronous Motor(PMLSM) is progressed for minimization of detent force owing to structure of slot-teeth and thrust ripple by harmonic magnetic flux of permanent magnet. The characteristics of thrust and detent force computed by Finite element Analysis are acquired equal effect both skewed basic model and optimum model which is optimization of permanent magnet shape.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9A
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• pp.830-837
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• 2005

ISI is caused by delay spread in the multipath channel environment. There are two kinds of channel equalizer: Linear and Non-Linear type according to the structures. In this paper, we propose an improved adaptive linear equalizer to mitigate ISI. The proposed adaptive equalizer is constructed by using asymmetrical Dsmvenu filter based on USE sub-optimal receiver. Asymmetrical structure of the transversal filter is realized by moving the main tap position from center to side. If this structure is used, we can divide ISI to precusor and postcusor. As a result the proposed equalizer has a larger extended compensation range than conventional adaptive linear equalizer. In computer simulation, we compare the bit error rate performance of the proposed linear equalizer with the conventional one on the S-V channel which is modeled for WB systems.

• Journal of the Korea Convergence Society
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• v.11 no.10
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• pp.63-69
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• 2020

In this paper, a small microwave sensor that can be applied to a wearable device is proposed because it can detect the heartbeat signal of a human body moving irregularly at low speed. It consist of balanced microstrip radiation patches in the 2.4 GHz ISM band, self-oscillation detection circuit, and feedback circuit. Based on the theoretical development and simulation, the validity of the proposed structure was confirmed and the manufactured prototype was tested. The board size of the circuit is as small as 65mm × 85㎟, and has a low power consumption of 60mW thanks to the simple RF circuit structure. Finally heartbeat signal has been obtained from a human body moving at low speed (0.5Hz) within a linear distance of 2 to 30mm close to the sensor and a lateral distance of ±20mm.

• Earthquakes and Structures
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• v.12 no.5
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• pp.569-581
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• 2017

The Monte Carlo Simulation (MCS) based seismic fragility analysis (SFA) approach allows defining more realistic relationship between failure probability and seismic intensity. However, the approach requires simulating large number of nonlinear dynamic analyses of structure for reliable estimate of fragility. It makes the approach computationally challenging. The response surface method (RSM) based metamodeling approach which replaces computationally involve complex mechanical model of a structure is found to be a viable alternative in this regard. An adaptive moving least squares method (MLSM) based RSM in the MCS framework is explored in the present study for efficient SFA of existing structures. In doing so, the repetition of seismic intensity for complete generation of fragility curve is avoided by including this as one of the predictors in the response estimate model. The proposed procedure is elucidated by considering a non-linear SDOF system and an existing reinforced concrete frame considered to be located in the Guwahati City of the Northeast region of India. The fragility results are obtained by the usual least squares based and the proposed MLSM based RSM and compared with that of obtained by the direct MCS technique to study the effectiveness of the proposed approach.