• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.4
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• pp.567-573
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• 2002

In this paper, we propose a new symbol time synchronization scheme suitable for the OFDM system with an interpolator. The proposed scheme performs the following three steps. In the first step, the coarse symbol time synchronization is achieved by continuously measuring the average power of the received envelope signal. Based on this average power, the detection possibility for the symbol time synchronization is determined. It the signal is sufficient for synchronization, we next perform a relatively accurate symbol time synchronization by measuring the correlation between a short training signal and the received envelope signal. Finally, an additional frequency synchronization is performed with a long training signal to correct symbol synchronization errors caused by the phase rotation. From the simulation results, one can see that the proposed synchronization scheme provides a good synchronization performance over frequency selective channels.

• Journal of the Korea Convergence Society
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• v.11 no.2
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• pp.271-279
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• 2020

Squats and lunges are important exercises for strengthening the trunk and lower body among various free weight exercises. It should be achieved safe and effective excise through establishing of theoretical basis for exercise posture and standard movement. Therefore, it's necessary to develop the exercise model in order to prepare the scientific countermeasures for the prevent injuries and error movement through optimal exercise movement. For this purpose, it is effective to use appropriate instruments for motion compensation according to the optical motion and error motion. In this paper, we develop a motion model analysis system based on dynamic motion through the four-point load cell for dynamic motion analysis. Proposed analytical method, the optimal and the error motion numerical data is obtained through the dynamic motion analysis. And we verified that dynamic movement is simplified to establish the motion modeling according to the classification motion and the numerical quantification data for analyzing.

• Journal of the Korean Institute of Gas
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• v.2 no.1
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• pp.1-6
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• 1998

A low power (below than 300 mW) catalytic bead combusible gas sensor is developed and utilized with a computer controlled sampling system for measuring heat content of natural gas. The heat content of gas is proportional to the change in the energy required to exposure to the sample of combustible gas. The heat content of natural gas samples ranging 36.30 - 39.88 $MJ/m^3$ is measured in the range of approximately $1\%$ error, which is comparable to its nominal heat content. Each gas represents a slightly different curve of sensitivity to sensor temperature. Thus all of the sensitivities are not equal to every temperature. In calibration process the choice of a optimum operating temperature is an important factor that influences the overall performance of the measurement system.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.6
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• pp.108-114
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• 1989

Introducing and optimizing bit-significance to the Hopfield model, ten highly correlated binary images, i.e., numbers "0" to "9", are successfully stored and retrieved in a $6{}8$ node system. Unlike many other neural network models, this model has stronger error correction capability for correlated images such as "6","8","3", and "9". The bit significance optimization is regarded as an adaptive learning process based on least-mean-square error algorithm, and may be implemented with Widrow-Hoff neural nets optimizer. A design for electro-optic implementation including the adaptive optimization networks is also introduced.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.3
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• pp.233-239
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• 2004

Smart material is used in various applications such as for glass frame, for medical instruments and for a part of sensors. Smart composite materials ran be applied to a part of aircraft and to the on-line monitoring system for industrial structures, using the shape memory effect. However, it is very difficult to simulate and analyze the shape memory effect in smart composites. In this paper, a two dimensional axisymmetric model was proposed to analyze the smart composite of one fiber and matrix using the finite element method(FEM). The finite element analysis was carried out in two renditions of the room temperature(293K) and a higher temperature (363K). The results we.e compared with the experimental results to confirm the validity of the analysis. In addition, the acoustic emission(AE) technique was used to study the microscopic damage behavior and the effect of pre-strains on TiNi/A16061 shape memory alloy composite.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.56.1-56.1
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• 2010

MIRIS(Multipurpose InfraRed Imaging System)는 과학기술위성 3호의 주 탑재체로서 2011년 발사예정인 다목적 적외선 카메라 시스템이다. MIRIS는 우주관측 카메라와 지구관측 카메라로 구성되어 있으며, 우주관측 카메라는 $0.9-2.0{\mu}m$ 영역에서 3.67 deg. x 3.67 deg. FOV로 우리 은하평면 survey 관측과 우주배경복사(CIB) 관측을 수행할 것이다. 현재 MIRIS는 비행모델 개발 마무리 단계에 있으며, 검교정 시험, 열-진공 시험, 진동 시험 등을 수행하고 나면 2010년 말 위성 본체와의 조립을 진행할 것이다. 우주관측 카메라는 궤도상에서 태양, 지구의 적외선 복사와 망원경과 검출기 주변에서 발생하는 열잡음을 줄이기 위해 냉각이 필요하며, 제한된 위성의 무게와 부피, 전력등의 요구조건들 때문에 망원경 및 구조체의 복사냉각(Passive Cooling) 방법을 선택하였다. Passive cooling으로 우주관측 카메라의 망원경이 200K 이하로 냉각되면, dewar에 설치된 소형 냉각기를 가동하여 적외선 센서를 80K로 냉각한다. 위성체 내벽과 우주관측카메라의 각 구조체들 사이의 복사를 차단하기위해 30층의 MLI를 적용 하였고, 각 구조체들간의 열전도를 최소화하기위해 GFRP supporter를 적용하였다. 이 실험은 천문(연)에서 자체 제작한 열-진공 챔버를 활용하여 진행하였으며, 이미 인증모델에 대한 passive cooling 실험을 두 차례 실시하였고, 그 실험 결과를 반영하여 최종 비행모델에 대한 실험을 수행하였으며, 그 실험 결과에 대해 논의 하고자 한다.

• Journal of Korea Multimedia Society
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• v.8 no.2
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• pp.287-295
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• 2005

For a quick and easy way of writing Hangul in hand-held devices, we analyzed the combination rules of Hangul alphabets that we constructed a small set of Hangul alphabets that combines a whole set of Hangul alphabets. Hangul consonants are generated from base set of consonants with function keys and vowels are constructed from eight base set of vowels by combination rules and stroke-adding rules. Especially, we adopted an easy error-correction method to resolve the inconvenience of using a delete key for vowel harmony errors. Futhermore, we diversified the input method of diphthongs for user-friendliness by minimizing the efforts of teaming vowel combination rules. We compared our method with previous methods of 'Chon-Ji-In' and 'Na-Rat-Keul' that the proposed method is better than the previous methods in input speed and error correction functionality.

• Journal of the Korean Society of Radiology
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• v.12 no.2
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• pp.133-138
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• 2018

The measurement of gamma-ray spectrum of $^{nat}W(p,xn)$ reaction with natural tungsten were performed by using a high energy proton generated from a 100-MeV proton linear accelerator of the Korea Multi-purpose Accelerator Complex (KOMAC). Gamma rays generated by various nuclides generated through the nuclide were measured using a gamma-ray spectroscopy system composed of HPGe detector. A gamma-ray standard source was used for energy calibration and efficiency measurement of the detector. Analysis of the gamma rays observed in the measured spectra showed that the radionuclides produced were $^{167}Re$, $^{178}Re$, $^{179}Re$, $^{180}Re$, $^{181}Re$, $^{182}Re$, $^{184}Re$, $^{172}Ta$, $^{174}Ta$, $^{178}Ta$, $^{182}Ta$, $^{184}Ta$, $^{175}W$, $^{176}W$, $^{177}W$ and $^{179}W$. Nuclides were generated. The results of this study will be applied to nuclear fusion, astrophysics, and nuclear medicine applications in the future.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.3
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• pp.187-192
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• 2017

This paper presents an ongoing study to develop a novel pressure sensor by means of a Nano Carbon Piezoresistive Composite (NCPC). The sensor was fabricated using the 3D printing process. We designed a miniaturized cantilever-type sensor electrode to improve the pressure sensing performance and utilized a 3D printer to build a small-sized body. The sensor electrode was made of 2 wt％ MWCNT/epoxy piezoresistive nano-composite, and the sensor body was encapsulated with a pipe plug cap for easy installation to any pressure system. The piezoresistivity responses of the sensor were converted into stable voltage outputs by using a signal processing system, which is similar to a conventional foil strain gauge. We evaluated the pressure-sensing performances using a pressure calibrator in the lab environment. The 3D-printed cantilever electrode pressure sensor showed linear voltage outputs of up to 16,500 KPa, which is a 200％ improvement in the pressure sensing range when compared with the bulk-type electrode used in our previous work.

• Fire Science and Engineering
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• v.21 no.1 s.65
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• pp.7-18
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• 2007

This research intended to show a reasonable way to improve working conditions of fire officers in Korea. It shows that fire officers have dignity of their social roles even though they have the unfairness in a work time, rewards, promotions and opportunities of overseas training compared with those of other government officers. The unfairness needs to be solved. In addition, there are more demands in fire fighters, but part of a regional government system already composed of 64.06% of fire officers, which means, there are too many fire fighters in one regional government. Therefore, it is difficult to employ more fire fighters. This is one of barriers to prevent from improvement of the working conditions. To improve the working conditions and to overcome the barriers, there are important solutions to counter the problems. Those are application of alternative policies and systems. Compared with the employment system and workload of fire officers in USA, Japan and other advanced countries, it is necessary to introduce alternative policies which include operation of partial three-shift system, expansion of oversees training, expansion of rotational-off system and improvement of employees' welfare policies.