• 대한방사선기술학회지:방사선기술과학
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• 제45권4호
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• pp.313-320
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• 2022

Both angiography and interventional procedures accompanied by angiography provide many diagnostic and therapeutic benefits to patients and are rapidly increasing. However, unlike general radiography or computed tomography using the same X-ray, the amount of radiation is quite high, but the dose range can vary considerably for each patient and operator. The high sensitivity of the lens to radiation during cerebral angiography and neurointervention is already well known, and although there are many related studies, it is insufficient to easily reduce radiation in diagnosis and treatment. In this situation, in particular, by adding three-dimensional rotational angiography (3D-RA) to the existing two-dimensional (2D) angiography, it is now possible to make an accurate diagnosis. However, since this 3D-RA acquires images through projection of more radiation than before, the exposure dose of the lens may be higher. Therefore, we tried to analyze whether the radiation dose of the lens can be reduced by moving the lens out of the field range by adjusting the table height and magnification ratio during the examination using 3D-RA. The surface dose was measured using a rando phantom and a radiophotoluminescent glass dosimeter (PLD) and the radiation dose was compared by adjusting the table height and magnification ratio based on the central point. As a result, it was found that the radiation dose of the lens decreased as the table height increased from the central point, that is, as the lens was out of the field of view. In conclusion, in 3D-RA, moving the table position of about 2 cm in height will make a significant contribution to the dose reduction of the lens, and it was confirmed that adjusting the magnification ratio can also reduce the surface dose of the lens.

• 한국식품조리과학회지
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• 제7권4호
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• pp.71-86
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• 1991

This study was attempted to enhance nutritional value of cooked rice by adding milk in cooking water. Cooked and soaked rice with five different levels of milk in cooking water (0%, A: 30%, B: 50%, C: 70%, D: 100%, E) was tested for rheological parameters, fine structural changes, sensory evaluation. 1. Water absorbance of raw rice in cooking water with varying amountes of milk, was tested at $5^{\circ}C$ and $15^{\circ}C$ for 2 hours. Water absorption ratio was decreased as milk content was increased and soaking temperature was low. Time for maximum water absorption of sample A was 40 min at 1$15^{\circ}C$ but for sample B to D, it was not reached until 120 min. 2. Electronmicroscopic observation revealed that starch granules of rice lost their regular forms by soaking for 90 minutes, but recovered most of initial regularity after 24 hours. Increase in milk content of soaking water decreased marginal sharpness of the starch granule, presumably due to reduced swelling of the granule. 3. Degree of gelatinization of cooked rice was highest in sample A and progressively decreased as milk content was increased. It was, however, increased in all samples when the cooking water to rice ratio was raised from 160% to 180%. During 4 hour storage, rates of retrogradation were not different between A and B samples, but those of C, D and E were about 2.5 times higher than A and B under the optimal condition of 170% cooking water to rice ratio. This was in the order reverse to hardness order of AC>A, D＞E at cooking water to rice ratios of 160% and 170%, above which A sample surpassed the rest of samples. 4. Sensory evaluation conducted by fifteen university students as panelists showed that there were more significant differences among five samples in flavour, texture than appearance and a notable preference for b and C over A, D and E.

• Structural Engineering and Mechanics
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• 제56권4호
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• pp.507-534
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• 2015

The present work investigates the behavior of the embankment models resting on soft soil reinforced with ordinary and stone columns encased with geogrid. Model tests were performed with different spacing distances between stone columns and two lengths to diameter ratios (L/d) of the stone columns, in addition to different embankment heights. A total number of 42 model tests were carried out on a soil with undrianed shear strength $${\sim_\sim}10kPa$$. The models consist of stone columns embankment at s/d equal to 2.5, 3 and 4 with L/d ratio equal 5 and 8. Three embankment heights; 200 mm, 250 mm and 300 mm were tested for both tests of ordinary (OSC) and geogrid encased stone columns (ESC). Three earth pressure cells were used to measure directly the vertical effective stress on column at the top of the middle stone column under the center line of embankment and on the edge stone column for all models while the third cell was placed at the base of embankment between two columns to measure the vertical effective stress in soft soil directly. The performance of stone columns embankments relies upon the ability of the granular embankment material to arch over the 'gaps' between the stone columns spacing. The results showed that the ratio of the embankment height to the clear spacing between columns (h/s-d) is a key parameter. It is found that (h/s-d)<1.2 and 1.4 for OSC and ESC, respectively; (h is the embankment height, s is the spacing between columns and d is the diameter of stone columns), no effect of arching is pronounced, the settlement at the surface of the embankment is very large, and the stress acting on the subsoil is virtually unmodified from the nominal overburden stress. When $(h/s-d){\geq}2.2$ for OSC and ESC respectively, full arching will occur and minimum stress on subsoil between stone columns will act, so the range of critical embankment height will be 1.2 (h/sd) to 2.2 (h/s-d) for both OSC and ESC models.

• 한국안광학회지
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• 제20권4호
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• pp.455-462
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• 2015

목적: 친수성 콘택트렌즈 정점굴절력 측정 방식중 하나인 wet cell 측정법을 활용한 국산화 측정 홀더와 프로그램 개발에 관한 연구를 위해 현재 사용되어지고 있는 Poster wet cell 홀더와 함수율별 굴절력의 측정값을 비교 분석하였다. 방법: 안경원에서 사용 중인 기존 제품과 새롭게 개발된 국산제품에 식염수를 채워 넣고 소프트콘택트렌즈의 굴절력을 측정하였다. 실험에 사용한 친수성 콘택트렌즈는 안경원에서 많이 사용되고 있는 국내산 렌즈를 사용하였으며, 함수율별과, 구면굴절력별로 분류하여 각각 실험하였다. 결과: wet cell 방식으로 콘택트렌즈 굴절력 측정 시 새롭게 개발한 홀더의 경우 자동렌즈미터를 사용하여 굴절력을 측정한 결과 -3.00 D에서 함수율 38%는 -3.01 D, 함수율 45%는 -3.00 D, 함수율 58%는 -2.98 D로 측정되었으며, Poster wet cell 홀더를 사용하여 렌즈를 측정한 결과 -3.00 D에서 함수율 38%는 -3.60 D, 45%는 -3.06 D, 58%는 -2.46 D로 각각 측정되었다. 결론 : 고함수율에서 굴절력 측정값은 wet cell 방식의 두 홀더 모두 낮게 나타났으며, 새롭게 개발된 홀더와 프로그램을 통한 자동렌즈미터의 측정값이 기존의 Poster soft contact lens wet cell 측정방식에 비해 더 정확한 굴절력 측정 결과를 나타내었다.

• 방송공학회논문지
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• 제10권3호
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• pp.321-327
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• 2005

조명 변화에 적응적인 움직임 탐색 및 보상 방법과 2차원 다이렉트 모드 (2D Direct Mode)를 이용한 MVC (Multi-view Video Coding) 방법을 제안한다. 먼저, 공간적 및 시간적으로 인접한 영상으로부터 휘도 화소 값의 움직임 탐색 및 보상을 수행하기 위한 새로운 SAD (Sum of Absolute Difference) 측정 방법을 제안한다. 조명 변화에 적응적인 움직임 탐색 및 보상은 움직임 벡터의 정확도를 높이고, 비트의 절감을 위하여 새로운 SAD 계산식을 사용한다. 다음으로, 시점 간의 예측 시에 사용될 수 있는 2차원 다이렉트 모드는 MPEG-4 AVC의 시간적 다이렉트 모드 (Temporal Direct Mode)로부터 확장된 방식이다. 본 논문에서 제안된 MVC 방법은 MPEG-4 AVC의 Simulcast 부호화와 비교하여 약 0.8dB의 PSNR (Peak Signal-to-Noise Ratio) 향상을 보였다.

• 한국정보통신학회논문지
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• 제20권4호
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• pp.721-727
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• 2016

본 논문에서는 기존 알고리즘에서의 특정 D2D 사용자 분포에 대한 광고확산 효율 저하 문제를 해결하기 위해, D2D 통신 네트워크에서 광고확산 효율을 개선하는 광고확산 알고리즘 기반의 Modified Single Linkage, K-means, 그리고 Gaussian mixture model을 적용한 Expectation Maximization 클러스터링 알고리즘의 적용이 제안되었다. 제안된 클러스터링 알고리즘들을 통해 광고 확산을 위한 목표지역들이 목표그룹으로 클러스터링되고 이를 통해 D2D 전송 단말과 수신 단말 사이의 거리를 기반으로 광고 확산 경로 설정 알고리즘과 릴레이 단말 설정 알고리즘이 적용되어 광고가 연속적으로 전파된다. 본 논문에서는 MATLAB 시뮬레이션을 통해 각 알고리즘의 최대 D2D 릴레이 제한 수와 목표지역과 비목표지역의 사용자 밀집도의 비에 따른 성능을 비교 분석한다.

• Journal of Advanced Marine Engineering and Technology
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• 제32권4호
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• pp.550-556
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• 2008

The aim of this research is to analyze the influence of motive pressure, driving nozzle position and nozzle throat ratio on the performance of ejector. The experiment was conducted in the variation of motive pressure of 0.196, 0.294, 0.392 and 0.490MPa respectively. The position of driving nozzle was varied in difference locations according to mixing tube diameter(0.5d, 1d, 2d, 3d, 4.15d, 5d and 6d). The experimental results show when the nozzle outlet is located at 3d, the flow characteristics change abruptly. It is shown that the suction flow rate and pressure lift ratio of ejector is influenced by the driving nozzle position. At nozzle position location of the Id of mixing tube diameter the performance of ejector gives the best performance.

• Bulletin of the Korean Chemical Society
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• 제31권5호
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• pp.1289-1294
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• 2010

Novel $H_8$-binaphthol-based chiral receptors appended with an uryl moiety (2a) and a guanidinium moiety (2b) have been designed and synthesized for the enantioselective recognition of 1,2-amino alcohols via reversible imine formation. The selectivities ($K_R/K_S$ = 9.8 ~ 19.4) of 2b in imine formation with 1,2-amino alcohols are higher than those of 2a ($K_R/K_S$ = 1.8 ~ 4.5). Similar efficiency trend have been observed in the conversion of L-amino acids to D-amino acids, i.e., the efficiency of the receptor 2b (D/L ratio: 4.3 ~ 10.1) is superior to 2a (D/L ratio: 4.0 ~ 8.7).

• Geomechanics and Engineering
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• 제2권4호
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• pp.303-319
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• 2010

The effect of grain crushing on the deformation of sand in 1D compression and 1D creep at high stresses was investigated theoretically and experimentally. An approach was proposed to formulate the process of grain crushing in sand in accordance with the laws of fracture mechanics and energy conservation. With this approach, the relation between the void ratio and the amount of grains crushed in 1D compression was derived. Laboratory test data were used to verify this derived relation. In addition, it was observed that there are similarities in evolution of grain size distribution in 1D compression and 1D creep tests. This implies that the changes in microstructure in sand under 1D compression and 1D creep are comparable.

• 한국전자파학회논문지
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• 제18권2호
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• pp.158-165
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• 2007

본 논문은 X-band에서 동작하는 마이크로스트립 원형 편파 $4{\times}4$ 배열 안테나의 설계와 제작에 대해 다룬다. 단일 안테나는 정사각형 패치를 사용하고 비대칭 십자 개구 결합 급전 구조를 사용하여 RHCP(Right Handed Crcularly Polarization)로 동작하도록 하였다. 기존의 배열 안테나의 소자간의 간격을 0.8 ${\lambda}_0$에서 0.45 ${\lambda}_0$로 간격을 줄여 실장 면적을 감소시켰다. 급전 선로는 시퀀셜 로테이션 분배기로 $2{\times}2$ 배열 안테나를 설계하여 양호한 이득과 축비 대역폭을 나타내었다 ${\lambda}/4$ Transformer와 T-junction 전력 분배기로 $4{\times}4$ 배열 안테나로 확장하였다. 시뮬레이션으로 확인한 결과 최대 방사 이득은 15.09 dBi로 나타났으며, 축비 대역폭은 3 dB 기준 $9.05{\sim}10.4$ GHz(13.5%)의 양호한 특성을 보였다. 제작된 $4{\times}4$배열 안테나는 10 GHz에서 측정 결과 임피던스 대역폭($VSWR{\leq}2$)은 $8.45{\sim}11.84$ GHz(33.9%)로 나타났으며, 최대방사 이득은 11.10 dBi를 얻었다. 또한 측정된 축비 대역폭은 $9.42{\sim}10.47$ GHz(10.5%)를 얻었다.