• 한국산학기술학회논문지
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• 제1권2호
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• pp.27-31
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• 2000

대상 물체의 온도분포를 해석하고 계측하기 위해 열상 장비가 구현된다. 시스템의 주요한 부분은 초점면 배열 형태의 센서가 적용된 열상 카메라이다. 적용된 열상 센서는 중파장 적외선 영역의 신호를 검출하며 열상을 형성하기 위한 기본 신호를 출력한다. DSP가 활용되어 센서 신호처리를 통해 열상을 구성하고 NTSC 신호 및 디지털 신호 출력을 한다. 열상의 화질을 개선하기 위해 이점 교정법을 적용한다. 이는 낮은 온도와 높은 온도를 기준으로 하여 초점면 배열 센서 화소 신호의 공간적인 비균일함을 교정하는 것으로서 실험 결과를 통해 열상의 화질이 개선됨을 보인다.

• Journal of Communications and Networks
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• 제13권6호
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• pp.655-663
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• 2011

Diffuse optical wireless (DOW) systems have the advantage that they do not require point-to-point siting so one transmitter can communicate with several receivers. In this paper, we investigate multiple access scheduling methods for downlink orthogonal frequency division multiplexing (OFDM) in diffuse optical wireless networks. Unlike the radio frequency (RF) channel, the DOW channel has low-pass filter characteristics and so requires different scheduling methods than those developed for the RF channel. Multi-user diversity orthogonal frequency division multiple access (OFDMA) systems nominate a cluster of subcarriers with the largest signal-to-noise-ratio for transmission. However, in a DOW channel, most users would choose the lowest frequency clusters of subcarriers. To remedy this problem, we make two proposals. The first is to use a variable cluster size across the subcarriers; the lower frequency clusters will have fewer subcarriers while the higher frequency clusters will have more subcarriers. This will equalize the capacity of the clusters. The second proposal is to randomize a user's cluster selection from a group of clusters satisfying a minimum threshold. Through simulation it is shown that combining these strategies can increase the throughput while ensuring a fair distribution of the available spectrum.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.418-421
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• 2003

Today, much terminologies such as noise spectrum, Sharpness, contrast, MTF had been defined for Image quality revaluation of radiation Image. Since development of Xeroradiography In the 1970s, Digital radiation detector that use amorphous selenium was developed. The aim of this research is to analyze physical phenomenon of digital radiation detector that use amorphous selenium. Result of Monte Carlo simulations on amorphous selenium based on physical properties(creation of electron-hole pairs) by induced x-ray are described. From the simulation, intrinsic point spread function(PSF) was found and used to observe modulation transfer function(MTF). We investigated how PSF and MTF changed with various x-ray energy. This result can be used to design digital x-ray detector based on a-Se.

• 한국정보기술응용학회:학술대회논문집
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• 한국정보기술응용학회 2005년도 6th 2005 International Conference on Computers, Communications and System
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• pp.255-258
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• 2005

A blind-mode integer frequency offset estimation algorithm is proposed for an OFDM system. Imperfect integer frequency offset estimation causes ambiguity in the data sub-carrier position. Morelli's blind integer frequency offiet estimation algorithm exploits the likelihood function by comparing the power in sub-carriers. It, however, shows performance degradation when there is the fractional frequency offset. The proposed algorithm solves this by using interpolation in the frequency domain. In this algorithm, it is exploited that the effect of the frequency offset is shown as a shift of power spectrum. By calculating the covariance of over-sampled samples, most approximate samples to integer point are obtained. It enables integer frequency offset estimation less affected by fractional frequency offset.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1994년도 FIFTH WESTERN PACIFIC REGIONAL ACOUSTICS CONFERENCE SEOUL KOREA
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• pp.791-795
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• 1994

In this paper, the echo phenomena of Yingying Pagoda(ancient Chinese architecture), which may be resulted from interferences of reflection and diffraction by the pagoda eaves when pulse sound source is at some suitable positions, are investigated by an 1:2 scale model. There are valleys in frequency spectrum due to the interferences. On the other hand, taking eaves as wedges approximately, numerical spectral estimates are obtained from the closed-form impulse solution for diffraction of pulse point-source radiation by an infinite rigid wedge. The results of the numerical computations are similar to those of the model experiments. The study is a helpful guide to reconstruction or maintenance of this kind of ancient buildings.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1631-1633
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• 2000

A study was carried out on the effect of VDF mol%, on the phase transition presented by P(VDF/TrFE) copolymer cast from dimethylformamide(DMF) solution with molar ratios 70/30 and 80/20. The results from dielectric spectrum and differential scanning calorimetry(DSC) showed that the phase transitions from ferroelectric to paraelectric phase(Curie transition) were observed The Curie point slightly has shifted to high temperature with increasing in VDF mol%, however, the melting point has shifted to low temperature.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1489_1490
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• 2009

Ground impedance is changed according to frequency of the current injected into the grounding system. Because the lightning surge gives a broad frequency spectrum from some ten Hz to a few MHz, frequency dependance of ground impedance must be evaluated. In this paper, we have constructed 10m, 30m, 50m counterpoise and evaluated frequency dependance of ground impedance. Also we have evaluated frequency dependance of ground impedance according to current injection point. As a result, long counterpoises have low ground resistance, but ground impedances of those are significantly increased in the range of high frequency. In the case that currents are injected into the center of counterpoise, the ground impedance is most lower than any other injection point. Also, additory ground rod of 1.8m long affect ground impedance decrease.

• 한국전자파학회논문지
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• 제19권6호
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• pp.630-639
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• 2008

본 논문에서는 전파 잡음에 노출된 무선 랜의 데이터 전송 속도 저하(低下)가 일어나는 원인과 주파수 이격(離隔)에 따른 간섭 정도가 달라지는 이유를 설명하였고, 또한 현저한 전송 속도 저하를 일으키는 간섭파의 전계 강도 수치를 측정하였다. 연구에 사용된 두 대의 무선 랜 및 한 대의 AP(Access Point)가 무선 통신망을 형성하였다. 사용된 전파 간섭의 종류는 동일 채널 간섭 및 인접 채널 간섭이었고, 각 경우에 대한 전계 강도 임계 수치를 도출하였다. 두 경우의 전파 간섭에 대한 전계 강도 임계 수치를 조사한 결과, 그 값은 54 dBuV/m @3 m이었고, 이 수치는 현행 국내 기준치인 30.9 dBuV/m @3 m보다 높은 값이었다. 이는 802.11b 무선 랜에 관한 한은, 국내의 소출력 무선기기 규정치는 23.1 dB 만큼 과도하게 설정되었음을 의미하는 것이다.

• 산업진흥연구
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• 제9권1호
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• pp.167-177
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• 2024

본 논문의 목적은 궁위 인식에 대한 학술적 지위를 조금이나마 회복시켜 보는 데 목적이 있다. 근묘화실로 비유되는 궁위론, 즉 연월일시의 상징성은 단순한 통변의 기술이 아니다. 사주의 가장 근간을 이루는 명리 원리에 해당한다는 점을 인식하고 그 학술적 연구가 앞으로 더 많이 이루어져야 한다는 취지에서 연구하였다. 사주를 구성하는 내재적 사상은 음양오행이며, 기록하는 글자는 십간십이지이고, 시공의 자리를 담당하는 요소는 천간, 지지 그리고 4개의 기둥으로 엮인 궁위(宮位)이다. 이번 궁위 인식에 관한 고찰을 통해 인간이 탄생하는 시점, 즉 우주의 에너지가 뇌와 온몸에 포맷되는 그 순간에 과거의 시간과 정보가 시간의 점을 통과하고 스펙트럼처럼 확산되며 미래의 시간과 행동을 이끌어 간다는 '시간의 스펙트럼' 현상을 궁위론의 근거로 제시해 보았다. 임철초가 '원형이정'을 설명하는 근거로 사용한 선･후천팔괘의 변화 포인트와 현대 우주론 중 하나인 평행이론에서 가정하고 있는 현재를 투과하고 있는 두 원뿔형의 시간 변화 혹은 왜곡이 미래의 우주에 잔상을 남긴다는 가정을 궁위론의 연역적 근거로 삼아 논의해 보았다.

• Nuclear Engineering and Technology
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• 제52권5호
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• pp.1029-1035
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• 2020

The detector suffers from pulse pileup by overlapping of the signals when it was used in high radiation fields. The pulse pileup deteriorates the energy spectrum and causes count losses due to random co-incidences, which might not resolve within the resolving time of the detection system. In this study, it is aimed to propose a new pulse pileup correction method. The proposed method is to correct the start point of the pileup pulse. The parameters are obtained from the fitted exponential curve using the peak point of the previous pulse and the start point of the pileup pulse. The amplitude at the corrected start point of the pileup pulse can be estimated by the peak time of the pileup pulse. The system is composed of a NaI (Tl) scintillation crystal, a photomultiplier tube, and an oscilloscope. A 61 μCi ¹³⁷Cs check-source was placed at a distance of 3 cm, 5 cm, and 10 cm, respectively. The gamma energy spectra for the radioisotope of ¹³⁷Cs were obtained to verify the proposed method. As a result, the correction of the pulse pileup through the proposed method shows a remarkable improvement of FWHM at 662 keV by 29, 39, and 7%, respectively.