• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1455-1458
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• 2005

This paper presents the method of reducing torque ripple of Blushless Direct Current(BLDC) motor. In the BLDC motor, the torque is decided by the back-EMF and current waveform. If the back-EMF is constant, the torque ripple depends on the current ripple during commutation period. The current in commutation period is acquired by circuit analysis and then the torque ripple simply can be reduced by varying input voltage to flow the current continuously. And suggested method is confirmed by dynamic with parameters of 500W BLDC motor.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.11
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• pp.1434-1444
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• 1995

Current test has recently been known to be a promising testing method in CMOS VLSI because conventional voltage test can not make sure of the complete detection of bridging, gate-oxide shorts, stuck-open faults and etc. This paper presents a new BIC(built-in current sensor) for the internal current test in CMOS logic circuit. A single phase clock is used in the BIC to reduce the control circuitry of it and to perform a self- testing for a faulty current. The BIC is designed to detect the faulty current at the end of the clock period, so that it can test the CUT(circuit under test) with much longer critical propagation delay time and larger area than conventional BICs. The circuit is composed of 18 devices and verified by using the SPICE simulator.

• Steel and Composite Structures
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• v.13 no.2
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• pp.139-155
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• 2012

Serviceability rather than strength is the most critical design requirement for vibration-vulnerable floor constructions. Annoying vibrations due to normal walking activity have been observed more frequently on long-span lightweight floor systems in office and commercial retail buildings, raising the need for the development of floor vibration design procedures. This paper highlights some limitations of one of the most commonly used guidelines AISC/CISC DG11, and proposes improvements to this method. Design charts and approximate closed form formulas to estimate the walking response are developed in which various factors relating to the dynamic characteristics of both the floor and the excitation are considered. The accuracy of the proposed formulas and other proposals found in the literature is examined. The proposed modifications would be significant, especially with long-span floors where vibration levels may be underestimated by the current design procedure. The application of the proposed prediction method is illustrated by worked examples that reveal a good agreement with results obtained from finite element analyses and experiments. The presented work would enhance the accuracy and maintain the simplicity and convenience of the design guideline.

• Proceedings of the KIEE Conference
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• 1992.07a
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• pp.503-505
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• 1992

This paper describes the optimization of design variables of SLIM using finite element method and SUMT(Sequential Unconstrained Minimization Technique). Thrust is taken as an objective function in order to maximize thrust under constant current drive, and seven independent design variables and nine constraints are chosen. As a result, $\tau$/g(pole pitch/airgap) and $\tau$/$d_{AL}$(pole pitch/aluminum depth) of good criteria in SLIM design are determined.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.3
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• pp.191-198
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• 1998

This paper presents a new current control method to reduce the torque ripple due to phase commutation, when the unipolar PWM method is applied for the phase current control of brushless DC motor. Phase commutation bring about an instantaneous change in the average voltage of conducting phase so that current undulates, and this undulating current generates torque ripple. In this paper, we analyze average voltage variations of conducting phase in commutation period with PWM pattern and design current controller to compensate average variations. In addition, we prove the validity of proposed method by experimental results.

• Current Optics and Photonics
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• v.3 no.3
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• pp.193-198
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• 2019

We propose a novel method to design a dispersion map for a WDM (Wavelength Division Multiplexing) ring network with the capability of wavelength reconfiguration. The method is simple, but gives us an optimum set of DCMs (Dispersion Compensation Modules) which satisfies a given value of the tolerable residual dispersion. The proposed method does not depend on compensation method, fiber type, or modulation format. We also demonstrate numerically how it works with an example 10-node ring network.

• Journal of the Korean Society of Safety
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• v.31 no.6
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• pp.19-24
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• 2016

One of key parameters on lightning protection system design of electric, information and communication system is grounding impedance. Earth impedance includes numerous information about earthing performance of grounding system. This paper suggests grounding impedance measuring device which is comprised of wideband current source, voltage and current measuring components. We used IQ Demodulation to measure more accurate phase difference of voltage and current. The range of frequency is up to 1 MHz that is IEEE defined as the range of lightning surge. We compared developed grounding impedance measuring device with existing one to test its performance, and we used grounding system while we implemented measurement and analysing by using fall of potential method IEEE Std.81 proposed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.2
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• pp.363-368
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• 2009

In the paper, we confirmed improvement Noise figure of the entire RF front-end using spiral inductor with PGS(Patterned Ground Shield) and current bleeding techniques. LNA design is to achieve simultaneous noise and input matching. Spiral inductor in input circuit of LNA inserted PGS for betterment of Q-factor. we modeling inductor using EM simulator, so compared with inductor of TSMC 0.18um. We designed and simulation the optimum structure of PGS using Taguchi's method. We confirmed enhancement of noise figure at LNA after substituted for inductor with PGS. Mixer designed using current bleeding techniques for reduced noise. We designed LNA using inductor with PGS and Mixer using current bleeding techniques, so confirmed improvement of noise figure.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.327-334
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• 2002

This paper develops an optimized torsional design method of asymmetric wall structures considering deformation capacities of walls. Contrary to the current torsional provisions, a deformation based torsional design is based on the assumption that stiffness and strength are dependent. Current torsional provisions specify two design eccentricity of stiffness to calculate the design forces of members. But such a methodology leads to an excessive over-strength of some members and an optimal torsional behavior is not ensured. Deformation-based torsional design uses displacement and rotation angle as design parameters and calculates base shear for inelastic torsional response directly. Because optimal torsional behavior can be defined based on the deformation of members, deformation based torsional design procedure can be applied to the optimal and performance-based torsional design. To consider the effect of accidental eccentricity, an over-strength factor is defined. The over-strength factor is determined from performance level, torsional resistance and arrangement of walls.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.4
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• pp.807-814
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• 1994

One case of pointwise limit design is performed for a hyperbolic paraboloid saddle shell(originally used by the Lin-Scordelis) to check the design strength against a consistent design loads, therefore, to verify the adequacy of current design practice for reinforced concrete shells. The design method which was based on stresses from membrane analysis in conjunction with pointwise limit state design equations shows a good performance, which means that the design method gives a lower bound on the ultimate load. This shows the adequacy of the current practice at least for this saddle shell case studied. To generalize the conclusion many more designs-analyses are performed with different shell configurations.