• 한국통신학회논문지
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• 제34권3C호
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• pp.304-310
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• 2009

본 논문은 M-레벨 QAM 계층 변조 시스템에서 반복 수신기의 복잡도를 줄이기 위한 연속 MAP(maximum a posteriori probability) 검파 방식을 제안한다. 계층 변조 신호 내의 특정 우선 순위를 갖는 신호는 계층 변조 신호를 구성하는 각 신호를 우선 순위에 따라 간섭 신호 성분으로서 제거하거나 가우시안 잡음으로 간주한 후 MAP 방식에 의해 순차적으로 검파된다. 검파 과정을 순차적으로 진행함으로써 반복 수신의 복잡도를 신호 당 전송되는 비트 수에 선형적으로 증가하도록 감소시킬 수 있으며 각 부호화 비트의 연판정 값 계산 시 간섭 제거와 가우시안 가정의 효과를 검파 과정에 반영하여 잡음 분산을 조정함으로써 순차적 검파 방식에 의해 발생할 수 있는 성능 열화를 최소화한다. 전산 모의 실험을 통하여 제안하는 순차적 MAP 검파 방식의 성능이 최적 MAP 검파 방식과 비교하여 0.5dB 미만의 성능열화를 나타내는 것을 보인다.

• 대한방사선기술학회지:방사선기술과학
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• 제45권2호
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• pp.127-134
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• 2022

In order to overcome the image quality limitations of the conventional C-arm, a flat panel detector (FPD) is used to enhance spatial resolution, detective quantum efficiency, frame rate, and dynamic range. Three-dimensional (3D) visualized information can be obtained from C-arm computed tomography (CT) equipped with an FPD, which can reduce patient discomfort and provide various medical information to health care providers by conducting procedures in the interventional procedure room without moving the patient to the CT scan room. Unlike a conventional C-arm device, a C-arm CT requires different basic safety and essential performance evaluation criteria; therefore, in this study, basic safety and essential performance evaluation criteria to protect patients, medical staff, and radiologists were derived based on International Electrotechnical Commission (IEC) standards, the Ministry of Food and Drug Safety (MFDS) standards in Korea, and the rules on the installation and operation of special medical equipment in Korea. As a result of the study, six basic safety evaluation criteria related to electrical and mechanical radiation safety (leakage current, collision protection, emergency stopping device, overheating, recovery management, and ingress of water or particulate matter into medical electrical (ME) equipment and ME systems: footswitches) and 14 essential performance evaluation criteria (accuracy of tube voltage, accuracy of tube current, accuracy of loading time, accuracy of current time product, reproducibility of radiation output, linearity and consistency in radiography, half layer value in X-ray equipment, focal size and collimator, relationship between X-ray field and image reception area, consistency of light irradiation versus X-ray irradiation, performance of the mechanical device, focal spot to skin distance accuracy, image quality evaluation, and technical characteristic of cone-beam computed tomography) were selected for a total of 20 criteria.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2009년도 한국우주과학회보 제18권2호
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• pp.48.1-48.1
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• 2009

In recent years, many candidates for extra-solar planet have been discovered from various measurement techniques. Fueled by such discoveries, new space missions for direct detection of earth-like planets have been proposed and actively studied. TPF instrument is a fair example of such scientific endeavors. One of the many technical problems that space missions such as TPF would need to solve is deconvolution of the collapsed (i.e. spatially and temporally) spectral signal arriving at the detector surface and the deconvolution computation may fall into a local minimum solution, instead of the global minimum solution, in the optimization process, yielding mis-interpretation of the spectral signal from the potential earth-like planets. To this extend, observational and theoretical understanding on the spectral bio-signal from the Earth serves as the key reference datum for the accurate interpretation of the planetary bio-signatures from other star systems. In this study, we present ray tracing computational model for the on-going simulation study on the Earth bio-signatures. A multi-layered atmospheric model and sea ice variation model were added to the existing target Earth model and a hypothetical space instrument (called AmonRa) observed the spectral bio-signals of the model Earth from the L1 halo orbit. The resulting spectrums of the Earth show well known "red-edge" spectrums as well as key molecular absorption lines important to harbor life forms. The model details, computational process and the resulting bio-signatures are presented together with implications to the future study direction.

• 천문학논총
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• 제11권1호
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• pp.109-123
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• 1996

We have developed a 5GHz continuum receiver system. The receiver is a direct type receiver. In order to reduce the noise due to the fluctuation of the gain in the amplifiers, the system employs the Dicke switching method. We made the 5GHz low-noise amplifier and the bandpass filter. The low-noise amplifier gives ${\sim}35dB$ gain and has ${\sim}210K$ noise temperature. The bandpass filter has a passband between 4.3 and 5.4GHz. We also made switch driver, video amplifiers, phase detector, and integrator. Using a 1.8 meter offset parabolic antenna, we measured the efficiency of the system. Since the antenna does not have a driver to track objects, observations were performed with the antenna fixed. The measured noise temperature of the system is ${\sim}650K$. From the observation of the blank sky, noise level was measured. It was found that the systematic noise(${\sim}0.5K$: peak to peak value) is much larger than the thermal noise. The systematic noise is possibly related to the stability of the DC power supplied to the receiver system. Besides the noise of the system, it was found that the airplanes are the very serious noise sources. We measured the radio flux of the Sun using the developed system. The observed radio flux of the Sun is ${\sim}10^6Jy$, which is close to the known value of the quiet Sun. The test observation of the Sun shows that the angular beam size of the antenna is ${\sim}2.2^{\circ}$.

• 치과방사선
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• 제22권2호
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• pp.273-282
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• 1992

The purpose of this study was to propose the utility which was evaluated the digital image processing and clinical application of the videodensitomery. The experiments were performed with IBM-PC/16bit-AT compatible, video camera(CCdtr55, Sony Co., Japan), an color monitor(MultiSync 3D, NEC, Japan) providing the resolution of 512×480 and 64 levels of gray. Sylvia Image Capture Board for the ADC(analog to digital converter) was used, composed of digitized image from digital signal and the radiographic density was measured by 256 level of gray. The periapical radiograph(Ektaspeed EP-21, Kodak Co., U. S. A) which was radiographed dried human mandible by exposure condition of 70 kVp and 48 impulses, was used for primary X-ray detector. And them evaluated for digitzed image by low and high pass filtering, correlations between aluminum equivalent values and the thickness of aluminum step wedge, aluminum equivalent values of sound enamel, dentin, and alveolar bone, the range of diffuse density for gray level ranging from 0 to 255. The obtained results were as follows: 1. The edge between aluminum steps of digitized image were somewhat blurred by low pass filtering, but edge enhancement could be resulted by high pass filtering. Expecially, edge enhancement between distal root of lower left 2nd molar and alveolar lamina dura was observed. 2. The correlation between aluminum equivalent values and the thickness of aluminum step wedge was intimated, yielding the coefficient of correlation r=0.9997(p<0.00l), the regression line was described by Y=0.9699X+0.456, and coefficient of variation amounting to 1.5%. 3. The aluminum equivalent values of sound enamel, dentin, and alvolar bone were 15.41㎜, 12.48㎜, 10.35㎜, respectively. 4. The range of diffuse density for gray level ranging from 0 to 255 was wider enough than that of photodenstiometer to be within the range of 1-4.9.

• 한국지리정보학회지
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• 제21권1호
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• pp.1-11
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• 2018

MMS(Mobile Mapping System) 자료를 이용한 정밀 공간 정보 매핑은 고정밀 3차원 지형 모델 구축, 시설물 관리를 위해 중요하며, 특히 도로 중앙선 매핑 작업은 정밀 도로 지도 구축을 위해 필요하다. 본 연구에서는 MMS LiDAR(Light Detection And Ranging) 자료를 이용하여 정밀 공간 정보인 도로 중앙선을 매핑 하는 반자동화 방법을 개발하였다. 우선 주어진 MMS LiDAR 자료를 기반으로 보간법을 이용하여 반사강도 영상을 제작하고, 에지 검출기를 이용하여 반사강도 영상으로부터 선형 세그먼트들을 추출하였다. 최종적으로 추출된 선형 세그먼트들 중에서 도로 중앙선 세그먼트를 수동으로 선택하였다. 추출된 도로 중앙선의 정확도 검증 결과, 0.065m의 정확도를 보여주었으며, 도로 중앙선이 도로 신호와 인접한 일부 지역에서 에러가 발견되었다.

• 한국방사선학회논문지
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• 제13권5호
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• pp.749-755
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• 2019

본 연구에서는 관전압과 관전류량이 디지털 방사선영상에서 적용되고 있는 노출 지수에 미치는 영향을 알아보고자 하였다. 방사선발생장치는 인버터방식의 디지털 X선 발생장치를 사용했으며 영상검출체는 포터블 형태의 무선 디텍터를 그리드 없이 사용하였다. 방사선영상은 3D 프린터를 이용하여 제작한 원뿔형 피라미드 팬텀을 이용하여 획득하였다. X선의 관전압 조사조건은 40 kVp부터 120 kVp까지 10 kVp 씩 증가시켰고 각 관전압에서 관전류량은 1 mAs에서부터 128 mAs까지 배수적으로 증가시켰다. 그 결과 관전압이 EI와 높은 $R^2$ 값으로 로그 함수적 관계가 있었으며 관전류량이 매우 높은 선형적인 관계가 있었다. 또한 영상 검출체의 면적선량과 EI도 $R^2$ 값이 0.76 이상으로 높은 상관관계가 있었다. 결론적으로 관전류량이 EI에 선형적으로 영향을 주었으며, 적절한 영상품질 유지를 위해서는 예측이 용이한 관전류량을 주로 조절하는 것이 유리하다고 판단된다.

• Journal of Radiation Protection and Research
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• 제30권2호
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• pp.69-75
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• 2005

기체전자증폭기(GEM, gas electron multiplier)는 동박이 양면으로 도포된 절연기관에 미세구멍배열을 형성한 박막으로 기존의 기체형 방사선 검출기의 미약한 방사선 신호를 증폭하기 위해 널리 사용되어지고 있다. 미세구멍 내부에 강한 전기장을 형성함으로써 이 내부로 유입되는 전자에 충분한 에너지를 전달, 전자사태를 유도하는 원리를 이용한다. 따라서 GEM의 특성은 GEM을 포함한 방사선 검출기에 인가되는 전압 즉, 전기장의 분포에 의해 결정된다. 따라서 올바르지 못한 전기장의 분포에 대해서는 신호 전자가 수집전극으로 향하지 못하고, GEM의 상 하단의 전극으로 이동, 신호의 손실을 초래할 수도 있다. 본 논문에서는 GEM의 가장 중요한 성능 지표 중 하나인 1차 전자수집효율(primary electron collection efficiency)을 계산하였다. 방사선에 의해 발생된 전자는 전기력선을 따라서만 움직인다는 가정 하에, GEM의 단위 구조에 대해 표류전극에서의 전기력선의 수에 대한 수집전극에서의 전기력선의 수의 비로 전자수집효율을 계산하였다. 전기력선의 계산은 3차원 유한요소법을 이용하여 계산하였다. 본 논문에서 사용한 방법은 가장 이상적인 상황으로 국한되지만, GEM의 설계 및 최적 운전변수 도출에 유용하게 사용될 수 있을 것이다.

• Natural Product Sciences
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• 제21권1호
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• pp.20-24
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• 2015

Cyanidin-3-glucoside (C3G) and cyanidin-3-rutinoside (C3R) were isolated by high-performance countercurrent chromatography (HPCCC) using a two-phase solvent system composed of tert-butyl methyl ether/n-butanol/acetonitrile/water/trifluoroacetic acid (1 : 3 : 1 : 5 : 0.01, v/v) to give pure C3G (34.1 mg) and C3R (14.3 mg) from 1.5 g crude mulberry fruit extract. Using the pure C3G and C3R, a reliable high-performance liquid chromatography (HPLC) method was developed and validated to determine the C3G and C3R contents in mulberry fruit. C3G and C3R were separated simultaneously using an Eclipse XDB-C18 column ($4.6{\times}250mm$ I.D., $5{\mu}m$) coupled with a photodiode array detector (PDA). The gradient elution of the mobile phase consisting of acetonitrile (0.5% formic acid) and water (0.5% formic acid) was applied (1.0 mL/min), and the detection wavelength was 520 nm. The calibration curves of C3G and C3R showed good linearity (both with $r^2=0.9996$) in the concentration range $15.625-500{\mu}g/mL$, and the relative standard deviations (RSD%) of intra- and inter-day variability were in the ranges 2.1 - 8.2% and 4.1 - 17.1%, respectively. The accuracies were ranged 96.5 - 102.6% for C3G and C3R, respectively. The developed HPLC method was used to determine the contents of C3G and C3R in newly harvested mulberry from eight different provinces of Korea.

• 대한한의학회지
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• 제30권3호
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• pp.98-105
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• 2009

Objective: Increased aortic and carotid arterial augmentation index (AI) is associated with the risk of cardiovascular disease. The most widely used approach for determining central arterial AI is by calculating the aortic pressure waveform from radial arterial waveforms using a transfer function. But how the change of waveform by applied pressure and the pattern of the change rely on subject's characteristics has not been recognized. In this study, we use a new method for measuring radial waveform and observe the change of waveform and the deviation of radial AI in the same position by applied pressure. Method: Forty-six non-patient volunteers (31 men and 15 women, age range 21-58 years) were enrolled for this study. Informed consent in a form approved by the institutional review board was obtained in all subjects. Blood pressure was measured on the left upper arm using an oscillometric method, radial pressure waves were recorded with the use of an improved automated tonometry device. DMP-3000(DAEYOMEDI Co., Ltd. Ansan, Korea) has robotics mechanism to scan and trace automatically. For each subject, we performed the procedure 5 times for each applied pressure level. We could thus obtain 5 different radial pulse waveforms for the same person's same position at different applied pressures. All these processes were repeated twice for test reproducibility. Result: Aortic AI, peripheral AI and radial AI were higher in women than in men (P<0.01), radial AI strongly correlated with aortic AI, and radial AI was consistently approximately 39% higher than aortic AI. Relationship between representative radial AI of DMP-3000 and peripheral AI of SphygmoCor had strongly correlation. And there were three patterns in change of pulse waveform. Conclusion: In this study, it is revealed the new device was sufficient to measure how radial AI and radial waveform from the same person at the same time change under applied pressure and it had inverse-proportion to applied pressure.