• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.1
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• pp.78-84
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• 2011

Using sensors to detect current or voltage of motors is disadvantaged because motor is exposed to vibration, impacts, corrosion, high temperature and humidity in the machinery structure like HEV. In the case of IPMSM, position information is included not only in the flux or EMF term but also in the rotator inductance because of its saliency. To solve this problem, a new mathematical model of IPMSMs on fixed frame is proposed and an extended EMF includiing rotating position information is defined to estimate extended EMF. A strong low-pass filter through the variable cut-off frequency using velocity function was proposed. This makes it is possible to estimate extended EMF by least order disturbance observer. The proposed method was proved through the experiment.

• Journal of the Korea Society of Computer and Information
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• v.8 no.3
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• pp.163-169
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• 2003

This study was carried out develope a motor power change speed device of motor by used micro- controller. This system was producted a auto-change speed device which switching frequency was 1,000MHz by used a auto- controller. It had a continuous output current such as 5A, 11A, 25A, 35A, 50A. It used a variable voltage from 9V to 18V(Maximum). We designed hardware of and software of micro-controller, we are made up of a auto cut-off function by 3.7V for detected power-loss prevention.

• Journal of Electrical Engineering and information Science
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• v.2 no.5
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• pp.129-133
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• 1997

A circuit model for a field emission triode has been proposed. The model parameters have been extracted from he fabricated silicon tip array and verified by comparing with the results simulated by circuit simulator(SPICE). The cut-off frequency can be calculated from the parametric capacitance and the transconductance values extracted from measurements. For the field emission triode, the capacitance of 3.45fF/tip and the transconductance of 0.94nS/tip have been measured under the emission current of 4.1nA/tip. From these values, the cut-off frequency is predicted to be 43 kHz but th measured one came out to be 6 kHz. because o the parasitic capacitance components.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.55-58
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• 2000

SiGe heterojuction bipolar transistors (HBT) have been studied and applied for advanced high speed integrated circuits. Device characteristics of SiGe HBT depending on the Ge profile of the transistor base region have been analysed using a device simulator, ATLAS/BLAZE. The models and parameters have been calibrated to the measured characteristics of the device, having a trapeziodal base profile, including the cut-off frequency of 45GHz and the dc current gain of 200. The Ge concentration which increases linearly, exponentially, or root-functionally from the emitter-base junction to the base-collector junction, has been tried to find out the influence on the device characteristics. The cut-off frequency and gain rather strongly depends on the exponential and root-functional Ge base profiles, respectively.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1784-1786
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• 1996

It is necessary to eliminate the broad band noise which frequency is in a few kHz to MHz in the AC line to supply the power to electrical and electronic control equipments. Because this kind of noise could damage the device or could be a source of malfunction, many devices like a filter and surge suppressor are developed to cut off the noise. But those device could not disconnected from the power line, so it remain some problem and on be used in limited area, In this paper, we present performance test results NCT(noise Cut Transformer) with excellent performance for reducing the high frequency noise and surge existing in the power line.

• Structural Engineering and Mechanics
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• v.73 no.6
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• pp.651-666
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• 2020

In this study, the spatial variation mechanisms of large far-field earthquakes at engineering scales are first investigated with data from the 2008 Ms 8.0 Wenchuan earthquake. And a novel 'coherency cut-off frequency' is proposed to distinguish the spatial variations in ground motions in the low-frequency and high-frequency ranges. Then, a practical piecewise coherency model is developed to estimate and characterize the spatial variation in earthquake ground motions, including the effects of source-to-site distances, site conditions and neighboring topography on these variations. Four particular earthquake records from dense seismograph arrays are used to investigate values of the coherency cut-off frequency for different source-to-site distances. On the basis of this analysis, the model is established to simulate the spatial variations, whose parameters are suitable for both near- and far-field earthquake conditions. Simulations are conducted to validate the proposed model and method. The results show that compared to the existing models, the proposed model provides an effective method for simulating the spatial correlations of ground motions at local sites with known source-to-site distances.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.2
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• pp.312-317
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• 2015

In this paper, the RF characteristics of multi-finger MOSFETs were improved by decreasing the parasitic capacitance in spite of increased gate resistance in a 90-nm CMOS technology. Two types of device structures were designed to compare the parasitic capacitance in the gate-to-source ($C_{gs}$) and gate-to-drain ($C_{gd}$) configurations. The radio frequency (RF) performance of multi-finger MOSFETs, such as cut-off frequency ($f_T$) and maximum-oscillation frequency ($f_{max}$) improved by approximately 10% by reducing the parasitic capacitance about 8.2% while maintaining the DC performance.

• Journal of Sensor Science and Technology
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• v.29 no.5
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• pp.324-327
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• 2020

The impact of output conductance (g_o) on the short-circuit current-gain cut-off frequency (f_T) in In_0.8Ga_0.2As high-electron-mobility transistors (HEMTs) on an InP substrate was investigated. An attempted was made to extract the values of f_T in a simplified small-signal model (SSM) of the HEMTs, derive an analytical formula for f_T in terms of the extrinsic model parameters of the simplified SSM, which are related to the intrinsic model parameters of a general SSM, and verify its validity for devices with L_g from 260 to 25 nm. In long-channel devices, the effect of the intrinsic output conductance (g_oi) on f_T was negligible. This was because, from the simplified SSM perspective, three model parameters, such as g_{m_ext}, C_{gs_ext} and C_{gd_ext}, were weakly dependent on g_oi. However, in short-channel devices, g_oi was found to play a significant role in degrading f_T as L_g was scaled down. The increase in g_oi in short-channel devices caused a considerable reduction in g_{m_ext} and an overall increase in the total extrinsic gate capacitance, yielding a decrease in f_T with g_oi. Finally, the results were used to infer how f_T is influenced by g_oi in HEMTs, emphasizing that improving electrostatic integrity is also critical importance to benefit fully from scaling down L_g.

• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.3
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• pp.240-249
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• 2004

In the present paper efforts have been made to optimize InAlAs/InGaAs HEMT by enhancing the effective gate voltage ($(V_c-V_off)$) using pulsed doped structure from uniformly doped to delta doped for microwave frequency applications and reliability. The detailed design criteria to select the proper design parameters have also been discussed in detail to exclude parallel conduction without affecting the del ice performance. Then the optimized value of $V_c-V_off$and breakdown voltages corresponding to maximum value of transconductance has been obtained. These values are then used to predict the transconductance and cut-off frequency of the del ice for different channel depths and gate lengths.

• The Journal of the Korea Contents Association
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• v.11 no.4
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• pp.414-427
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• 2011

The Means-end theory has successfully been applied in academics circles and is one of the qualitative methodologies, aiming at classifying into groups based on the specific values that they pursue. The more specific purposes of this study is to identify the relationship between the levels of abstraction and HVM(Hierarchical Value Map) and to identify the statistical changes in frequency activated cell and ladders among A-C-V. And lastly, to suggest the HVM according to the levels of abstraction. The subjects of this study includes the 100 hikers who joined the hiking at least once a year for 2007. The results of analysis show that as the level of abstraction goes up, the HVM itself is depicted more simple and the loss of information is also occurred. Consequently, the decision of levels of abstraction is should be made on the basis of objective validity.