• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.5
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• pp.971-978
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• 2018

This paper deals with the design and implementation of a limiter, which is a key component of the Ku-band radar system. The limiter design with the multi-pin diode switch was complemented by wideband signal attenuation, and realized the physical implementation. In the test result of implemented limiter, when the pin diode switch is all off, it is possible to transmit the incoming signal without distortion. Also when the pin diode switch is turned on sequentially, the input signal is attenuated about 20dB or more step by step. Finally when all of them were turned on, attenuation about 50dB or more were measured for a wide bandwidth(1000MHz) in Ku-band.

• Korean Journal of Applied Biomechanics
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• v.12 no.1
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• pp.15-30
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• 2002

The purpose of this study was analyzed the effect of kinematical and kinetical factors of lower extremity of form change in the cause of growth an unborn child during in pregnancy. Three pregnant women were selected from pregnant 24 weeks as subjects. Each subjects were required to walk with usual walking speed. Cinematographic and GRF data were collected during walking, and the kinematical and kinetical variables were calculated using Kwon3d. Based on the results of the study, the following conclusions were drawn : 1. Step width and Step length The change of form during the period of pregnancy was not statistically found significant in the step width and the step length. 2. Angle of lower extremity 1) The change of form during the period of pregnancy was not statistically found significant in the hip angle at right heel contact, mid stance, but it was statistically found significant in the hip angle at toe off on p<.05. 2) The change of form during the period of pregnancy was not statistically found significant in the knee angle at right heel contact, mid stance, but it was statistically found significant in the knee angle at toe off on p<.05. 3) The change of form during the period of pregnancy was not statistically found significant in the ankle angle at right heel contact, mid stance, but it was statistically found significant in the ankle angle at toe off on p<.05. 3. Ground reaction force 1) The change of form during the period of pregnancy was statistically found significant in medial-lateral force(Fx) on p<.001. 2) The change of form during the period of pregnancy was not statistically found significant in post-anterior force(Fy). 3) The change of form during the period of pregnancy was statistically found significant in impulse force and minimum peak of vertical reaction force on p<.001, p<.01 but it was not statistically found significant in second maximum force.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.8
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• pp.704-710
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• 2017

The supply of the liquid oxygen into a rocket combustor is simply controlled by the 'on' and 'off' positions of a main oxidizer shut-off valve. However, the partially opened position of a three-position valve can control and optimize the engine start transients by regulating the liquid oxygen flow rate during the start-up of the engine. In this paper, the design and performances of a three-position pneumatic poppet valve, which is intended to be employed in liquid rocket engines, have been presented.

• The Journal of the Acoustical Society of Korea
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• v.19 no.5
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• pp.79-83
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• 2000

When passband ripple α/sub p/ and stopband attenuation α/sub s/ at the w/sub s/ where the stopband begins are specified in filter design, △α/sub s/ usually exceeds the specification by △α/sub s/ due to the necessity that the order n of the filter function be an integer. In this paper, we apply a trade-off method to remove the excess stopband attenuation △α/sub s/ for reducing the value of pole-Q and improving the characteristics of the Chebyshev filter function. We also apply the trade-off method of pole-Q reduction to the modified Chebyshev function, and then the 4 types of function have been analyzed to compare in frequency and time domain characteristics. The trade-off method reduces the pole-Q which influences the filter characteristics to maximum 49.6% without increase of the order n. Thus implies that they have the improved characteristics such as the reduced passband ripple and flatter delay characteristics as compared Chebyshev filter function before trade-off. And the unit step response shows shorter delay time and settling time in time domain performance.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.2
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• pp.47-55
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• 1998

Steady-state and transient performance for the medium scale civil aircraft turbofan engine was analyzed. Steady-state performance was analyzed on maximum take-off condition, maximum climb condition, and cruise condition. At 90％RPM of the low pressure compressor, the partload performance was economized. The transient performance was analyzed with cases of the step increase, the ramp increase, the ramp decrease, and the step increase and ramp decrease for the input fuel flow. For the transient performance analysis, work matching between compressor and turbine was needed. Modified Euler method was used the integration of residual torque in work matching equation. At all flight condition, the overshoot of the high pressure turbine inlet temperature was appeared in the step and ramp increase case, and the surge of high pressure compressor was appeared in the step increase case and the ramp increase case within 5.5 seconds of maximum climb condition.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.2
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• pp.142-148
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• 2006

In this paper, authors propose a novel step-up AC-DC converter operated with power factor correction (PFC) and with high efficiency. The proposed converter behaves with discontinuous current control (DCC) of input current. The input current waveform in the proposed converter is got to be a discontinuous sinusoid form in proportion to magnitude of at input voltage under the constant duty cycle switching. Therefore, the input power factor is nearly unity and the control method is simple. In the general DCC converters, the switching devices are turned-on with the zero current switching (ZCS). But turn-off of the switching devices is done at the maximum current. To achieve a soft switching at turn-off, the proposed converter uses a new partial resonant circuit, which results in the very low switching loss and the high efficiency of converter.

• Journal of the Institute of Convergence Signal Processing
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• v.10 no.3
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• pp.158-163
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• 2009

LMS(Least Mean Square) algorithm requires simple equation and is used widely because of the low complexity. If the convergence speed increase, LMS algorithm has a divergence in case of sharp environment changes. And if a stability increase, the convergence speed becomes slow. This algorithm based on a trade off between fast convergence and system stability. To improve this problem, VSSLMS (Variable Step Size LMS) algorithm was developed. The VSSLMS algorithm improved the convergence speed and performance as adjusting step size using error signal. In this paper, I-VSSLMS algorithm is proposed tor improve the performance of adaptive noise canceller in real-time environments. The proposed algorithm is applied to adaptive noise canceller using TMS320C6713 DSP board and we did simulation by real time. Then we compared performance of each algorithm and demonstrated that proposed algorithm has superior performance.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.6
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• pp.95-101
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• 2009

Among the adaptive noise cancellers (ANC), the least mean square (LMS) algorithm has probably become the most popular algorithm because of its robustness, good tracking properties, and simplicity of implementation. However, it has non-uniform convergence and a trade-off between the rate of convergence and excess mean square error (EMSE). To overcome these shortcomings, a number of variable step size least mean square (VSSLMS) algorithms have been researched for years. These LMS algorithms use a complex variable step method approach for rapid convergence but need high computational complexity. A variable step approach can impair the simplicity and robustness of the LMS algorithm. The proposed instantaneous gain control (IGC) algorithm uses the instantaneous gain value of the original signal and the noise signal. As a result, the IGC algorithm can reduce computational complexity and maintain better performance.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.5 no.4
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• pp.753-760
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• 2015

The Korean wine market is growing year by year recently especially in Off-trade market. It shows not just a part of the very few consumer-driven trend. The purchases of wine is always not so easy because the risk factors and failure points occur when buying wines. Most of wine consumers feel difficulties when buying wines at phase of previous step, buying step and after buying step. Wine consumers can be divided into the wine experts, wine lovers, novices, outsiders. To guide an wine buying with less failures to each representative of wine consumer characteristics and needs, user persona and scenario for the reduced failure were derived.

• Korean Journal of Applied Biomechanics
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• v.12 no.1
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• pp.47-61
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• 2002

The purpose of this study was to determined the force and moment of the ankle and the knee joint at different step length relative to the length of the lower extremity during a steady running. Six digital cameras(Qualisis) and a forceplatform(A.M.T.I) were used to obtain the kinematic data of the segments and kinetic data on the running at speed of 5.18m/s. The force and moment measured from six subjects participated in this study were limited to the support phase and their values were averaged at the moment of heel strike, mid stance, and toe off of a running for making a comparison between the condition 1(relative step length 1.1) and the condition 2(relative step length 1.4). It was concluded that internal forces except mediolateral force of the condition 2 were greater in the ankle and the knee joint than those of the condition 1, but all moments of condition 2 were greater from the descriptive statistic point of view. For the future study, it was needed to consider a number of subjects, a various running speed, and a individual step preference for applying generally results to the running strategy.