• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.741-745
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• 2001

Reliability and safety of steer-by-wire concepts can be achieved by redundant designs. This paper discusses the design of a fault tolerant concept for a force feedback actuator with a standard three-phase PMSM. In contrast to usual drives, the phases of the machine are separated electrically. This design allows driving the machine with two instead of three phases in case of a fault. A superimposed torque controller adjusts the influence of fault currents and torque harmonics in two-phase operation and guarantees smooth torque at the steering wheel

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.7
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• pp.1307-1313
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• 1992

The end-point position control of a flexible manipulator is a non-minimum phase system. The PD feedback of the end-point position is not stable in contrast with that of the hub jangle. However, the system can be stabilized conditionally by the feedback of both the hub rate angle and the end-point position. Even in the non-minimum system, the LQG/LTR control law is more systmatic controller design method than the classical control law which uses a root-locus technique.

• 열병합발전
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• s.30
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• pp.21-25
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• 2002

According to recent Korea Electric Power Company report, yearly distribution line brass cramp bolts failure summed up to 4,400 cases emerging as one of main local break-down causes. Naturally, the need for the investigation was proposed To determine the root cause of the cramp bolt failures, mechanical and metallurgical investigation were performed for 90 samples which collected from various sites. For the understanding of the geometric characteristics, stress distribution was evaluated by CAE program and proof load of each bolts was tested. The SEM&EDS was used for metallurgical investigation. Through the investigation, the root causes of failures were confirmed. All damaged bolts showed intergrannular fracture mode and the all fractured bolt showed ß phase morphology contrast to the a&ß mixture morphology of the non-damaged samples. Additionally, EDS analysis confirmed the existence of lead rich layer on grain boundaries.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.351-352
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• 2006

BSCCO thin films are fabricated by an ion beam sputtering method, and sticking coefficients of the respective elements are evaluated. The sticking coefficient of Bi element in BSCCO film formation was observed to show a unique temperature dependence; it was almost a constant value of 0.49 below about $730^{\circ}C$ and decreased linearly over about $730^{\circ}C$. In contrast, Sr and Ca, displayed no such remarkable temperature dependence. This behavior of the sticking coefficient was explained consistently on the basis of the evaporation and sublimation processes of $Bi_2O_3$. It was concluded that Bi(2212) thin film constructs from the partial melted Bi(2201) phase with the aid of the liquid phase of $Bi_2O_3$.

• Journal of Information Display
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• v.9 no.2
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• pp.22-27
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• 2008

We propose an optical configuration of a vertical alignment (VA) liquid crystal (LC) cell to eliminate the light leakage in the diagonal direction. VA LC cell has an excellent contrast ratio in the normal direction due to the no phase-retardation. However, change of the phase-retardation occurs in all directions, which causes the light leakage and deteriorates the characteristics of the dark state. We designed the LC cell structure composed of multiple combinations with two A-plates and two C-plates in order to achieve wide viewing property on the Poincare sphere. From calculations, we show that the proposed structure can improve the viewing angle characteristics by compensating for the light leakage in all directions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.323-326
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• 2000

In this study, we used Brewster-Angle Microscope(BAM) to study on the molecular orientation of monolayer on the water surface. The behaviors of molecules on three different subphase have been observed. Reproducible $\pi$-A isotherm have been obtained only on information about phase transition by molecular area. BAM facilitates the observation of morphology by optical anisotropy and thickness in monolayer and multilayers as BAM is shown to be sensitive to anisotropy of film. Every transition was found by BAM technique, either as a dramatic change in degree of contrast or as a sudden alteration of molecular action and $\pi$-A isotherm.

• Proceedings of the IEEK Conference
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• 2000.11b
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• pp.321-324
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• 2000

In this paper, we proposed a new visual cryptography scheme based on optical interference which improves the contrast and SNR of reconstructed images comparing with conventional visual cryptography method. We divided an binary image to be encrypted into n slides. To encrypt them, (n-1) random independent keys and one another random key by XOR process between four random keys were prepared. XOR between each divided image and each random key makes encrypted n encrypted images. From these images, encrypted binary phase masks can be made. For decryption all of phase masks should be placed together in the interferometer such as Mach-Zehnder interferometer.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.118-120
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• 2003

The behavior of viscous fingerings caused by an external force is investigated by using a two­phase lattice Boltzmann method. The effects of the modified capillary number, the viscosity contrast, and the modified Darcy-Rayleigh number on the instability of interfaces are found. The calculated wave numbers are in good agreement with the theoretical ones in the range of wave numbers smaller than 10, but the calculated ones tend to become smaller than the theoretical ones in higher wave numbers.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.2
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• pp.189-198
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• 2004

We consider the problem of whether the three-dimensional checkerboard has the connectivity. For this purpose, we first consider the problem of determining the effective conductivity of a checkerboard-shaped composite material by the Brownian motion simulation method. Specifically, we use the efficient first-passage-time technique. Simulation results show that the effective conductivity of the three-dimensional checkerboard increases faster than the two-dimensional counterpart as the contrast between the phase conductivities increases. This implies that the three-dimensional checkerboard's connectivity is stronger than the two-dimensional checkerboard's and thus each phase material of the three-dimensional checkerboard is more likely to be connected than not to be connected.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.6
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• pp.539-544
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• 2016

This paper improves Sherman's two-pulse method for angle estimation of two unresolved targets in phase comparison monopulse radar. The proposed method provides the angle information with only a single-pulse measurement instead of two pulses. The proposed method can estimate a single-target angle by single-target indicator, in contrast with previous techniques. The accuracy of angle estimation for proposed method is demonstrated by simulations.