• 대한방사선기술학회지:방사선기술과학
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• 제42권6호
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• pp.435-440
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• 2019

This is to study the accuracy of the actual size according to the TOD(table object distance; TOD) change when measuring blood vessels using angiography equipment, and to help the optimal selection of the device used accordingly. Balls similar to the size of common vessels were calibrated with TOD using 30 mm, 20 mm, 10 mm, 5 mm and acrylic phantoms, catheter calibration from 0 cm to 10 cm, 20 cm and 30 cm, respectively. It was measured whether there was a change in the measured value according to the change. The equipment used was GE Innova 3131 IQ equipment, and the image reconstruction method was GE AW4.7 post processing program. Two radiotechnologists were scanned three times by catheter calibration method and 3DRA(3dimension rotational angiography; 3DRA) volume rendering method. The independent sample T-test showed 0.981 (p> 0.05) to verify the significance between the two observers. As a result, in case of catheter calibration, the error rate at TOD 0 mm and 10 mm is within ± 10%, but when the TOD is changed to 20 mm and 50 mm respectively, the tolerance is ± 10% except for 30 mm ball exceeded. On the other hand, 3DRA was included within the tolerance range of ± 10% overall even when the TOD was changed from 0 mm to 50 mm. In the catheter calibration method, the larger the TOD, the larger the error range, and the 3DRA method was able to measure vascular vessels accurately close to the actual measurement without any consideration of the TOD.

• 한국정보통신학회논문지
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• 제1권2호
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• pp.209-220
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• 1997

직접위성방송(DBS)은 해상에까지 광범위한 방송서비스를 제공할 수 있는 매우 유용한 매체이다. 그러나 해상에서의 DBS 수신장치는 선박의 운항이나 동요의 상태에 관계없이 안테나가 위성을 계속 추적해야 하는 복잡한 제어장치를 필요로 한다. 본 연구는 한반도 연 근해를 항해하는 선박에서 Koreasat의 DBS를 수신할 수 있는 장치의 개발이 목표였으며, 특히 소형선박에 쉽게 탑재하고 사용할 수 있도록 다른 항법장비와 연계됨이 없이 장치의 독립적인 운용형태로 설계하였고 소형, 경량, 저가격화에 중점을 두었다. 그러므로 한반도 연·근해에서 koreasat의 탐색과 추적조건을 분석하고 이에 적합한 Az/El 2축 마운트를 설계하여 제작하였으며, 스텝트랙(step track) 방식에 의한 추적과 각속도 센서를 이용한 마운트의 동요보정 기능을 연구하였다. 실험을 위하여 장치를 탑재할 수 있는 선박운동 시뮬레이터를 제작하여 목표치의 동요를 구현하고, 추적과 동요보정에 따른 수신상태를 측정, 분석하면서 실험적으로 최적의 알고리즘을 구현하였다.

• Environmental Engineering Research
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• 제19권3호
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• pp.269-274
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• 2014

On-site sanitation systems are typically installed to treat grey and toilet wastewaters in areas without sewer and centralized treatment systems. It is well known that, due to inappropriate design and operation, treatment performance of these systems in developing countries is not satisfactory in the removal of pathogens and organic matters. This research aimed to investigate the hydraulic conditions occurring in some on-site sanitation systems and the effects of hydraulic retention times (HRTs) on the system performance. The experiments were conducted with a laboratory-scale septic tank (40L in size) and an actual septic tank (600L in size), to test the hydraulic conditions by using tracer study with HRTs varying at 12, 24 and 48 hr. The experimental results showed the dispersion numbers to be in the range of 0.017-0.320 and the short-circuit ratios in the range of 0.014-0.031, indicating the reactors having a high level of sort-circuiting and approaching complete-mix conditions. The removal efficiency of $BOD_5$ was found to be 67% and the $k_{30}$ values for $BOD_5$ was $2.04day^{-1}$. A modified complete-mix model based on the relationship between $BOD_5$ removal efficiencies and HRTs was developed and validated with actual-scale septic tank data having a correlation coefficient ($R^2$) of 0.90. Therefore, to better protect our environment and minimizing health risks, new generation toilets should be developed that could minimize short-circuiting and improving treatment performance.

• 한국지진공학회논문집
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• 제11권1호
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• pp.29-35
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• 2007

본 연구에서는 반복 횡하중을 받는 콘크리트충전 탄소섬유튜브기둥의 휨성능 평가실험을 수행하였다. 시험체의 단면형상은 각형과 원형이며 탄소삼유튜브의 두께 및 와인딩각도(winding angle)를 실험변수로 채택하였다. 모든 시험체는 건물의 한 층 높이와 유사한 높이를 갖는 full scale 크기로 제작되었으며 3대의 가력기(actuator)를 동시에 가동시켜 축하중과 횡하중을 가력하였다. 실험결과를 분석하여 기둥의 휨강도, 변형능력 및 에너지소산능력을 평가하였으며, 횡하중에 대한 기둥의 연성거동 또한 평가되었다.

• Current Photovoltaic Research
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• 제10권4호
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• pp.111-115
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• 2022

For the high efficiency of the photovoltaic module, a high-output solar cell, which is the basis of photovoltaic power generation, is required. As the light receiving area of the solar cell increases, the light receiving area of the photovoltaic module also increases. Accordingly, recent trend is to use large-area solar cells such as M6 and M8 instead of M2-based solar cells for manufacturing the photovoltaic module and a study on the mechanical stiffness of the module with increased size is required. In this study, a mechanical load test corresponding to IEC-61215 was performed among the reliability tests of large-area photovoltaic modules. In order to confirm the degree to which the mechanical load test affects the photovoltaic module, the output and EL images were checked by sequentially increasing the pressure by 600 Pa at a pressure of 2400 Pa. Also, factors such as output and efficiency of large-area photovoltaic modules were verified through mechanical load testing of actual large-area photovoltaic modules and the rate of change was very small at 1%.

• 상하수도학회지
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• 제30권1호
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• pp.33-40
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• 2016

In this study, a fluorescent silica nano particle is used as the surrogate for challenging test of membrane surface integrity. The particles are functionalized by a fluorescent dying agent so that as an ultraviolet light is imposed a bright fluorescent image from the particles can be taken. If a membrane surface is damaged and has a compromised part larger than the size of surrogate the fluorescent particles would pass through and contained in the permeate. An operator can directly notice whether the membrane surface is damaged or not by detecting a fluorescent image taken from the permeate. Additionally, the size of compromised part is estimated through analysing the fluorescent image in which we surmise the mass of particles included in the permeate by calculating an average RGB value of the image. The pilot scale experiments showed that this method could be applied successfully to determine if a membrane surface had a damaged parts regardless of the test condition. In the testing on the actual damaged area of $4.712mm^2$, the lowest error of estimating the damaged area was -1.32% with the surrogate concentration of 80 mg/L, flux of $40L/m^2/hr$ for 25 minutes of detection. A further study is still going on to increase the lowest detection limit and thus decrease the error of estimation.

• 한국지반공학회논문집
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• 제25권12호
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• pp.57-67
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• 2009

최근 시공기술이 발전함에 따라 댐 축조재료로 사용되는 조립재료의 최대입경은 수cm에서 1m이상에 달하고 있다. 실제 현장 원입도 시료에 대한 시험을 실시하는 것은 비용적으로 고가일 뿐만 아니라 기술적으로도 많은 문제가 존재하므로 일반적으로 상사입도 시료에 대하여 실내시험을 실시하고 그 결과를 실제 지반구조물의 설계 및 해석에 적용한다. 지반구조물에 대한 보다 정확한 거동특성을 예측하기 위해서는 입자크기에 따른 전단거동 특성의 변화를 파악하는 것이 필수적이라고 할 수 있다. 이에 본 연구에서는 국내 B댐 현장 댐 축조시료인 하상 사력재에 대하여 최대입경을 서로 달리하여 재구성한 상사입도시료를 대상으로 같은 상대밀도로 공시체를 제작하여 대형삼축시험을 실시하였으며, 최대입경의 변화에 따른 상사입도시료의 응력-변형특성, 전단강도특성을 비교.분석하였다. 시험결과 조립재료는 전단과정에서 응력연화 및 체적팽창 거동을 나타내고, 상사입도 시료의 최대입경이 증가할수록 그 현상이 더욱 뚜렷한 것으로 나타났다. 내부마찰각, 전단강도는 상사입도 시료의 최대입경이 증가함에 따라 증가하는 것으로 나타났다.

• 한국방사선학회논문지
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• 제5권5호
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• pp.223-229
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• 2011

X선은 X선관 내 음극측 전자(electron)를 빠른 속도로 가속시킨 다음 진행하는 전자의 흐름을 저지극(target)에서 차단시킬 때 에너지의 변환을 일으켜 발생한다. 가속된 고속의 전자가 저지면에 충돌하는 실제면적을 실초점(actual focal spot)이라 하고, 실초점의 크기를 X선이 나오는 방향인 중심선(central ray)측에서 관측할 경우 축소되어 작게 보이는데 이때의 초점을 실효초점(effective focal spot)이라고 한다. X선관 방사각에 따라 음극 측의 강도가 양극 측 보다 높게 나타나 X선 강도가 균등하지 않다. 이러한 효과를 경사각 효과(heel effect)라고 하며, 경사각 효과로 인하여 환자가 받는 피폭의 정도는 양극의 각도, 즉 실효초점의 크기에 따라 달라지게 된다. 본 논문에서는 실효초점의 크기와 그에 따른 환자 피폭선량의 상관관계를 알아보고 실효초점의 크기에 따른 균질선량 분포를 위한 효과적인 조사야를 제시하고자 한다. 결론적으로 초점크기에 따라서 평균적으로 -8cm ~ 0cm 범위에서 효과적인 조사야 범위를 찾을 수 있었고, 평균 선량률은 0.019 R/min이 나왔다. 이 범위를 이용하면 환자에게는 적은 피폭선량으로 균등한 흑화도 및 해상력을 가진 영상을 얻을 수 있을 것이다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.88-91
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• 2002

The two dimensional size effect of specimen gauge section (length x width) was investigated on the compressive behavior of a T300/924 [45/-45/0/90]3s, carbon fiber-epoxy laminate. A modified ICSTM compression test fixture was used together with an anti-buckling device to test 3mm thick specimens with a 30$\times$30, 50$\times$50, 70$\times$70, and 90mm$\times$90mm gauge length by width section. In all cases failure was sudden and occurred mainly within the gauge length. Post failure examination suggests that $0^{\circ}$ fiber microbuckling is the critical damage mechanism that causes final failure. This is the matrix dominated failure mode and its triggering depends very much on initial fiber waviness. It is suggested that manufacturing process and quality may play a significant role in determining the compressive strength. When the anti-buckling device was used on specimens, it was showed that the compressive strength with the device was slightly greater than that without the device due to surface friction between the specimen and the device by pretoque in bolts of the device. In the analysis result on influence of the anti-buckling device using the finite element method, it was found that the compressive strength with the anti-buckling device by loaded bolts was about 7% higher than actual compressive strength. Additionally, compressive tests on specimen with an open hole were performed. The local stress concentration arising from the hole dominates the strength of the laminate rather than the stresses in the bulk of the material. It is observed that the remote failure stress decreases with increasing hole size and specimen width but is generally well above the value one might predict from the elastic stress concentration factor. This suggests that the material is not ideally brittle and some stress relief occurs around the hole. X-ray radiography reveals that damage in the form of fiber microbuckling and delamination initiates at the edge of the hole at approximately 80% of the failure load and extends stably under increasing load before becoming unstable at a critical length of 2-3mm (depends on specimen geometry). This damage growth and failure are analysed by a linear cohesive zone model. Using the independently measured laminate parameters of unnotched compressive strength and in-plane fracture toughness the model predicts successfully the notched strength as a function of hole size and width.

• 한국식품영양학회지
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• 제28권5호
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• pp.871-879
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• 2015

24-hour recall is the dietary assessment method most frequently used to evaluate dietary intake; however, accuracy is an issue when using this method, especially in large-scale studies. The purpose of this study was to assess the validity of dietary intake estimation using one serving size. Estimates of energy and nutrients taken in over a 24-hr period based on actual intake amount (24HRAI) and based on estimates of one serving size (24HRSS) were compared. Data were analyzed using a paired t-test, Pearson's correlation coefficients, and a cross-classification method. In male subjects, intake levels of energy, fat, vitamin C, vitamin $B_1$, Zn, and total food measured using 24HRAI were significantly higher than those measured using 24HRSS. In female subjects, intake of carbohydrates, fiber, fat, vitamin A, vitamin C, vitamin B complexes, various minerals, and total food measured using 24HRAI were significantly lower than those measured using 24HRSS. Energy-adjusted Pearson's correlation coefficients revealed that intake of all nutrients showed a significant positive relationship between the two measurement methods in both males and females. Cross-classification analysis revealed that 50.5~67.6% of women and 40.3~71% of men were classified in the same quartile of intake of each nutrient when comparing data from 24HRAI and 24HRSS. We conclude that using one serving size in 24-hr recall analysis was valid and therefore may be used in studies to assess food consumption in the general adult population. Also, this method can be used to classify energy and nutrient intake into quartile, which is useful in examining the association between diet and chronic diseases.