• 대한원격탐사학회지
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• 제27권3호
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• pp.369-377
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• 2011

Since well-calibrated satellite data is critical for their applications, calibration and validation of COMS science data was one of the key activities during the IOT. COMS MI radiometric calibration process was divided into two phases according to the out-gassing of the sensor: calibrations of the visible (VI) and infrared (IR) channels. Different from the VIS calibration, the calibration steps for the IR channels followed additional processes to secure their radiometric performances. Primary calibration steps of the IR were scan mirror emissivity correction, midnight effect compensation, slope averaging and 1/f noise compensation after a nominal calibration. First, the scan mirror emissivity correction was conducted to compensate the variability of the scan mirror emissivity driven by the coating material on the scan mirror. Second, the midnight effect correction was performed to remove unreasonable high spikes of the slope values caused by the excessive radiative sources during the local midnight. After these steps, the residual (difference between the previous slope and the given slope) was filtered by a smoothing routine to eliminate the remnant random noises. The 1/f noise compensation was also carried out to filter out the lower frequency noises caused from the electronics in the Imager. With through calibration processes during the entire IOT period, the calibrated IR data showed excellent performances.

• 천문학회지
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• 제25권1호
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• pp.23-46
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• 1992

The electrical, mechanical and optical capabilities have been tested of the microdensitometer PDS 1010GMS at the Korea Astronomy Observatory. The highest stage of scan speed 255 csu (conventional speed unit) is measured to be 47 mm/s. At this speed the position is displaced by $4{\mu}m$ to the direction of scanning and the density is underestimated by $0.4{\sim}0.7D$. Standard deviation in the measured density is proportional to $A^{-0.46}$, where A is the area of scan aperture. The accuracy of position repeatability is ${\pm}1{\mu}m$, and that of density repeatability is ${\pm}(0.003{\sim}0.03)D$. Callier coefficient is determined to be 1.37; the semispecular density is directly proportional to the diffuse density up to 3.5D. Because the logarithmic amplifier has a finite response time, the densities measured at high scan speeds are underestimated to the degree that speeds higher than 200 csu are inadequate for making an accurate astronomical photometry. After power is on, an about 5 hour period of warming is required to stabilize the system electrically and mechanically as well. On the basis of this performance test, we have determined the followings as the optimum scan parameters for the astronomical photometry: For the scan aperture $10\;\sim\;20{\mu}m$ is optimal, and for the scan speed. $20\;{\sim}\;50$ csu is appropriate. These parameter values are chosen in such a way that they may keep the density repeatability within ${\pm}0.01D$, the position displacement under $1{\mu}m$, and the density underestimation below 0.1D even in high density regions.

• Childhood Kidney Diseases
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• 제10권2호
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• pp.201-212
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• 2006

Purpose : Vesicoureteral reflux(VUR) is the major risk factor of urinary tract infection(UTI) in children and may result in serious complications such as renal scarring and chronic renal failure. The purpose of this study was to evaluate the relationship between VUR and renal scar formation, the usefulness and correlation of various imaging studies in reflux nephropathy, and the spontaneous resolution of VUR. Methods : We retrospectively reviewed 106 patients with VUR with no accompanying urogenital anomalies in the Department of Pediatrics, Bundang CHA Hospital during the period from Jan. 1996 to Mar. 2005. Ultrasonography and $^{99m}Tc$-dimercaptosuccinic acid(DMSA) scan were performed in the acute period of UTI. Voiding cystourethrography(VCUG) was performed 1 to 3 weeks after treatment with UTI. Follow-up DMSA scan was performed 4 to 6 months after treatment and a follow-up VCUG was performed every 12 months. Results : The mean age at detection of VUR was $13.8{\pm}22.2$ months and the male to female ratio was 2:1. The incidence of renal scarring showed a tendency of direct correlation between severity of VUR(P<0.001) and abnormal findings of renal ultrasonography(P<0.01). 63.2%(24 of 38 renal units) of renal parenchymal defects present in the first DMSA scan disappeared on follow-up DMSA scans. Follow-up DMSA scans detected renal scars in 7(14%) of 50 renal units with ultrasonographically normal kidneys. Meanwhile, ultrasonography did not show parenchymal defects in 7(36.8%) of 19 renal units where renal scarring was demonstrated on a follow-up DMSA scan. The spontaneous resolution rate of VUR was higher(75%) in cases with low grade(I to III) VUR(P<0.01). Conclusions : The presence and severity of VUR and abnormal findings of renal ultrasonography significantly correlated with renal scar formation. DMSA scan was useful in the diagnosis of renal defects. Meanwhile renal ultrasonography was an inadequate method for evaluating renal parenchymal damage. Therefore, follow-up DMSA scans should be performed to detect renal scars even in children with low-grade VUR and normal renal ultrasonography.

• 한국통신학회논문지
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• 제31권5C호
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• pp.490-496
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• 2006

H.264는 현재 IP를 기반으로 하는 유무선 네트워크분야에서 많은 관심을 받고 있는 표준으로서 기존에 제정된 비디오 표준들보다 향상된 에러 복구 기술들을 포함하고 있다. 본 논문에서는 기존의 비디오 표준에서 사용되어 오던 raster scan 방식과 H.264의 에러 복구 기술들 중 하나인 FMO (flexible macroblock ordering) 방식에 에러 은닉 기술을 적용하여 에러 은닉의 성능이 정확히 온 인접한 매크로블락 수에 따라 좌우됨을 분석하고, 다양한 패킷 손실율에서의 성능을 보인다. 시뮬레이션 결과, FMO 방식이 raster scan 방식에 비해 손실없이 오는 인접한 매크로블락 수가 많아 에러 은닉에 의한 PSNR 성능이 $1{\sim}9dB$ 정도 향상되고, 특히 인트라 프레임 간격이 길고 패킷 손실율이 높은 경우에 FMO 방식에 의한 PSNR 성능 향상이 더 크다.

• Journal of Korean Neurosurgical Society
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• 제54권2호
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• pp.100-106
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• 2013

Objective : To investigate the cases of intracranial abnormal brain MRI findings even in the negative brain CT scan after mild head injury. Methods : During a 2-year period (January 2009-December 2010), we prospectively evaluated both brain CT and brain MRI of 180 patients with mild head injury. Patients were classified into two groups according to presence or absence of abnormal brain MRI finding even in the negative brain CT scan after mild head injury. Two neurosurgeons and one neuroradiologist validated the images from both brain CT scan and brain MRI double blindly. Results : Intracranial injury with negative brain CT scan after mild head injury occurred in 18 patients (10.0%). Headache (51.7%) without neurologic signs was the most common symptom. Locations of intracranial lesions showing abnormal brain MRI were as follows; temporal base (n=8), frontal pole (n=5), falx cerebri (n=2), basal ganglia (n=1), tentorium (n=1), and sylvian fissure (n=1). Intracranial injury was common in patients with a loss of consciousness, symptom duration >2 weeks, or in cases of patients with linear skull fracture (p=0.00013), and also more frequent in multiple associated injury than simple one (35.7%>8.6%) (p=0.105). Conclusion : Our investigation showed that patients with mild head injury even in the negative brain CT scan had a few cases of intracranial injury. These findings indicate that even though the brain CT does not show abnormal findings, they should be thoroughly watched in further study including brain MRI in cases of multiple injuries and when their complaints are sustained.

• 대한방사선기술학회지:방사선기술과학
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• 제35권1호
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• pp.45-50
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• 2012

국내병원 대부분의 CT검사실은 One Stop Services를 목표로 운영하여 예약환자는 물론이고 전처치가 준비된 외래환자의 경우 당일 CT검사를 수행하고 있다. 하지만 One Stop Service라는 목표에는 양적인 접근은 가능할지언정 지루한 대기시간, 직원의 불친절도 등에 의한 질적인 저하를 야기 시키게 되었고 환자와 보호자들의 민원을 발생시키는 등 검사에 대한 불만족으로 이어지기도 한다. 따라서 본 연구는 직원의 친절도 향상, CT검사에 대한 이해도 향상, CT검사실의 환경개선, 당일 CT검사 대기시간의 단축 등, CT검사를 받는 환자의 불편사항을 찾아 만족도 향상을 위한 방안을 도출하고자 한다. CT검사 외래환자 중 조영제를 투여하는 복부 CT검사 환자를 대상으로 하고 CT검사 외래환자의 만족도를 확인하기 위해 설문지를 사용하였으며 개선 활동 전인 48명, 개선 활동 후 41명, 총 89명의 설문지를 2011.4.1-2011.9.30까지 조사 하였다. 조사 방법은 직원의 친절도, CT검사 이해도, 환경 만족도는 설문을 통해서 조사하고 당일 CT검사 대기시간은 의료정보 통계로 조사하였으며 SPSS V. 15.0 을 이용하여 분석하였다. 개선 전과 개선 후의 전반적인 만족도를 비교한 결과 CT검사실 이용절차의 편리성은 Mean(SD) $5.83{\pm}2.06$에서 Mean(SD) $8.88{\pm}1.87$로 52.32%, 직원의 친절도는 Mean(SD) $7.15{\pm}1.72$에서 Mean(SD) $9.44{\pm}1.24$로 32%, 환경만족도는 Mean(SD) $5.90{\pm}1.89$에서 Mean(SD) $9.00{\pm}1.59$로 52.54%, CT검사의 이해도는 Mean(SD) $5.94{\pm}1.83$에서 Mean(SD) $9.05{\pm}1.70$로 52.36%가 각각 상승하였다. 또한 대기시간은 평균 25.33분에서 21.04분으로 약 16.93% 단축시키는 큰 효과를 얻을 수 있었고 병원의 경쟁력 강화와 수익 증대에도 기여할 것으로 사료 된다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2007년도 추계학술대회 논문집
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• pp.215-217
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• 2007

Recently, the demand for high definition TV is being increased by beginning of the digital broadcasting. The higher resolution of PDP is, the longer addressing time become, then, the sustain period for display image decreases. Because of the reason, dual-scan method which synchronously write information of an image on top and bottom of the screen is used for the high definition PDP. However, as the price competition of PDP becomes severe, we can`t avoid turning to a single-scan method which uses only a half of an expensive address IC. Accordingly, the sustain period becomes much shorter than prior method. In case of XGA level, it is impossible to display, eventually. In this paper, we are going to prove usefulness by realizing negative reset waveform and the driving circuit for high speed addressing.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권8호
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• pp.407-414
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• 2004

In this paper, a new gray scale expression method that divides the scan lines into multiple blocks is suggested. The proposed method can drive 16 sub-fields per 1 TV field in the panel with XGA ($1366{\times}768$) resolution. The on and off states of even subfields depend on the condition of odd subfields. The write address mode is used in the odd subfields, while the erase address mode is used in the even subfields. Because the ramp reset pulse is applied every 2 sub-fields, both the contrast ratio and the dynamic voltage margin are sufficiently obtained in comparison with previous AWD (Address While Display) methods. In realizing 16 subfields, shortening the scan time in the erase address period was important. The X bias voltage in the erase address period affected the minimum address voltage but did not the delay time of the address discharge. The delay time of the address discharge was affected by the address voltage and the time interval between the last sustain discharge and the scanning time. We also evaluated the dynamic false contour. New method shows an improved image quality in horizontal moving, but discontinuous lines were observed at the boundaries of each block in vertical moving

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계합동학술대회 논문집
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• pp.149-152
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• 2002

If the ambient temperature rises for AC PDP, some of the discharge cells are turned off because of the misfiring during address period. Particularly, the misfiring of the 'last scan line is more serious than that of the first. In order to compensate the misfiring in such that case, different addressing voltage is applied at each cell such as progressively increasing pulse voltage instead of constant one. As a result, the addressing time and discharge charge of the last scan line have become similar to those of the first scan line and the phenomenon of misfiring has disappeared.

• 전자공학회논문지
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• 제52권1호
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• pp.135-139
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• 2015

플라즈마 디스플레이 패널의 각 부화면 시간동안 기입 방전의 지연시간을 각각 조사하였고 오방전이 발생하지 않는 범위내에서 추가 주사전압의 높이를 다르게 인가하여 모든 부화면 시간동안 기입방전 지연시간을 단축시키기 위한 수정된 구동방법을 제시한다. AC PDP에서 첫번째 초기화 기간 동안 주사전극에 높은 상승 경사파 전압을 인가하여 약한 플라즈마 방전이 발생하고 셀 내부에서 프라이밍 입자와 벽전하 생성을 유도한다. 생성된 벽전하는 셀 내부 벽전압이 되므로 기입기간 중 기입전압과 더해져서 기입 방전을 일으킨다. 그러나 셀 내부의 벽전하는 시간이 지나면서 점차 소멸되므로 1 TV 프레임 시간 동안 각 부화면 시간동안 기입방전은 늦게 발생한다. 첫 번째 부화면 시간에는 초기화 기간 동안 상승 경사파를 갖는 높은 전압에 의해 벽전하가 많이 남아 있으므로 첫 번째 기입 방전은 다른 부화면 시간보다 빠르게 형성된다. 한편, 두 번째부터 마지막 부화면 시간까지의 기입 방전 생성시간은 셀 내의 벽전하 소멸에 의하여 점차적으로 늦어진다. 본 연구에서는 각 부화면 시간동안 기입방전의 시간지연을 조사하였고, 부화면 시간의 기입기간 마다 추가 주사전압을 다르게 인가하여 전체 기입방전지연시간을 단축시켰다.