• Journal of the Korean Society for Precision Engineering
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• v.11 no.2
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• pp.75-84
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• 1994

기계가공프로세스에서 절삭공구의 마멸과 채터진동은 공작기계의 가동율과 생산성을 크게 저해하는 요인이 되고 있다. 본 연구에서는 공구마멸과 채터현상이 혼재하는 상황에서, 이들 두 현상을 동시에 검출하는데, AE 및 가속도센서에서 검출된 신호와 AR계수 및 주파수대역 평균에너지를 특징입력으로 하는 인공신경회로망을 이용하였다. 그 결과, 공구마멸과 채터현상에 대응하는 서로 다른 신호특징의 차이를 동시에 식별하는 데 인공신경 회로망의 유용성을 입증하였으며, 시계열모델의 AR계수(70 .approx. 90%)보다는 주파수대역에너지법의 평균에너지 (80 .approx. 100%)를 신경회로망의 특징입력으로 하는 경우가 높은 성공률을 나타내었다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2509-2518
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• 2013

Augmented reality (AR) technology visualizes a real type object that cannot simulate in virtual reality technology by overlapping a virtual object and real object in a computer system. This study suggests a methodology and prototype system for applying AR system to rebar distribution work in a civil engineering project. Rebar work in civil engineering project is a representative activity that is progressed by empirical approach of skilled labor rather than formalized manual. AR technology improves the constructability of rebar work because AR tool can identify missing rebars and different rebars comparing with the drawings. AR system developed in this study can enhance the understanding of rebar work using 3D modeling with real image of construction site and save construction cost by reducing reconstruction work.

• Journal of the Korean Chemical Society
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• v.45 no.2
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• pp.111-115
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• 2001

The ignition of NH$_3$-NO-Ar mixtures was examined in the temperature renge of 1675-2391 K behind reflected shock waves. The ignition delay times were measured by monitoring pressure profiles and the OH emissions at 1.0 cm from the end wall. A correlation between ignition delay times and concentrations of gases could be summarized in the form of mass-action expression, To complement the experiment, computer modeling study of the ignition of NH$_3$-NO-Ar mixtures was carried out using various mechanisms reported previously. The sensitivity analysis shows the reaction of NH$_2$+NO${\rightarrow}$NNH+OH is the most important step in the ignition of NH$_3$-NO-Ar mixtures.

• Journal of IKEEE
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• v.23 no.3
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• pp.865-872
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• 2019

We developed a one-dimensional Ar fluid model running in DC-type applied voltage with a sine and a pulse waveform at the atmosphere pressure. We investigated the light emissions and efficiencies of ${\lambda}_{128nm}$, ${\lambda}_{727nm}$, ${\lambda}_{912nm}$ and ${\lambda}_{966nm}$ from the Ar excited particles. From the results, the light emission of ${\lambda}_{128nm}$ and ${\lambda}_{727nm}$ in the applied voltage with a sine waveform were almost two times as in DC voltage type. The shorter the switching time of applied voltage was, the more the light emissions of ${\lambda}_{128nm}$ and ${\lambda}_{727nm}$ were. We discussed the power consumption and Joule heating by charged particles.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6C
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• pp.561-570
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• 2009

Ultra-wideband communication systems based on impulse radio have merits that are possible for the high data rate transmission, high resolution ranging are positioning system. Conventionally, in order to accomplish these features, the high-speed ADC (Analog to Digital Convertor) is necessary to apply radio determination system operating in time domain. However, considering low rate - wireless personal area network (LR-WPAN) aims to low-cost hardware implementation, the expensive ADC converting GHz sampling per second is not appropriate. So, this paper introduces a low complex AR (Auto Regressive) model based non-coherent ranging scheme operating in frequency domain with using low-speed ADC utilizing analog Voltage Control Oscillator (VCO) mode for the frequency domain transformation. To verify the superiority of the proposed ranging and location algorithm working in frequency domain, the suggested IEEE 802.15.4a TG channel model is used to exploit affirmative features of the proposed algorithm with conducting the simulation results.

• Journal of the Korea Convergence Society
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• v.10 no.12
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• pp.487-494
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• 2019

Augmented reality (AR) or virtual reality is suitable to apply the contents of a textbook so as to be directly observable by learners. This study aimed to examine the applicability and technology acceptance of anatomy learning using AR in nursing students. This study was conducted in May 2019 with 17 nursing students who studied an anatomy textbook using AR and answered a questionnaire about technology acceptance and the usability of AR in combination with the anatomy textbook. Perceived usefulness was identified as an influencing factor on technology acceptance with 51.2% acceptance rate and thus should be taken into consideration in the development of learning strategies using new technological learning methods.

• Applied Chemistry for Engineering
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• v.10 no.4
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• pp.502-508
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• 1999

We prepared non-porous membrane on the $Al_2O_3$ substrate with the different pore by the size by the plasma polymerization of $CHF_3$. We studied the permeability characteristics of membrane by Ar treatment and the effect of substrate pore size on gas permeation mechanism. The selectivity was increased with Ar plasma treatment time and rf-power near the substrate to the cathode while the permeability was decreased. It was observed that the solution-diffusion model would be applied to non-porous layers while it is applied Knudsen diffusion model to the substrate. From the experimental observation, it could be concluded that the pore size of $Al_2O_3$ membrane influenced on the permeability and the selectivity.

• Progress in Medical Physics
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• v.10 no.3
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• pp.141-149
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• 1999

This research analyzed the HRV signals by using wavelet transform to observe the activities of autonomous nervous system in a sleep state. This research also restructured the HRV signals from electrocardiogram and by using coefficient which was obtained through wavelet transform, analyzed the signals by frequency bandwidth. Then compared the analyzed results with existing frequency analyzing method using AR model techniques. The suggested wavelet coefficient from power spectrum component in the study shows a similar tendency with the results from FFT or AR model technique. Therefore, it can be found that power spectrum analyzing method by wavelet coefficient is a useful as a tool for analyzing autonomous nervous system activities using HRV signals. Since the suggested method able to clearly depict the progression of change in time zone, which was once impossible with the existing methods, it is presumed that it will be useful in other physiological signals.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.6
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• pp.163-174
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• 2009

Applying the maximally polyphase decomposition and noble identity to the adaptive filter in subband structure, the conventional fullband affine projection algorithm is translated to the subband affine projection (SAP) algorithm. The Maximally polyphase decomposed SAP (MPDSAP) algorithm is a special version of the SAP algorithm, and its adaptive sub-filters have unity projection dimension. The weight updating formular of the MPDSAP is similar to that of the NLMS algorithm, so it may be more proper algorithm than other AP-type algorithms for many practical applications. This paper presents a new statistical analysis of the MPDSAP algorithm. The analytical model is derived for autoregressive (AR) inputs and the nonunity adaptive gain in the subband structure with the orthonormal analysis filters (OAF), The pre-whitening by the OAF allows the derivation of a simple-analytical model for the MPDSAP with the AR inputs and the nonunity adaptive gain.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.8
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• pp.1939-1951
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• 1994

This study introduces a new tool breakage detecting technology comprised of an unsupervised neural network combined with adaptive time series autoregressive(AR) model where parameters are estimated recursively at each sampling instant using a parameter adaptation algorithm based on an RLS(Recursive Least Square). Experiment indicates that AR parameters are good features for tool breakage, therefore it can be detected by tracking the evolution of the AR parameters during milling process. an ART 2(Adaptive Resonance Theory 2) neural network is used for clustering of tool states using these parameters and the network is capable of self organizing without supervised learning. This system operates successfully under the wide range of cutting conditions without a priori knowledge of the process, with fast monitoring time.