• Progress in Medical Physics
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• v.21 no.3
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• pp.261-273
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• 2010

For the use of Indirect-conversion CMOS (complementary metal-oxide-semiconductor) detectors for digital x-ray radiography and their better designs, we have theoretically evaluated the spatial-frequency-dependent detective quantum efficiency (DQE) using the cascaded linear-systems transfer theory. In order to validate the developed model, the DQE was experimentally determined by the measured modulation-transfer function (MTF) and noise-power spectrum, and the estimated incident x-ray fluence under the mammography beam quality of W/Al. From the comparison between the theoretical and experimental DQEs, the overall tendencies were well agreed. Based on the developed model, we have investigated the DQEs values with respect to various design parameters of the CMOS x-ray detector such as phosphor quantum efficiency, Swank noise, photodiode quantum efficiency and the MTF of various scintillator screens. This theoretical approach is very useful tool for the understanding of the developed imaging systems as well as helpful for the better design or optimization for new development.

• The Korean Journal of Malacology
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• v.19 no.1
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• pp.1-8
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• 2003

The present study was performed to describe the influence of water temperature and salinity on the filtration rates of the short-necked clam, Ruditapes philippinarum. The clams were collected at tidal flat near Yeosu city, Cheollanamdo, Korea, from July 2001 to August 2001. Diatoms, Phaeodactylum tricornutum (KMCC B-128), were indoor-cultured by f/2 medium, and were used to measure the filtration rate of the clams. Filtration rates of the clams were measured by indirect method. Cell concentrations of food organisms were determined by direct counting cells using the hemacytometer under the light microscope. The filtration rate of the clams increased with temperatures up to the optimum temperature, circa 25$^{\circ}C$. Above this optimum temperature, the filtration rate decreased drastically. Also the filtration rate of the clams increased with salinity up to 35 psu. The maximal filtration rates of the clams were recorded at 20-25$^{\circ}C$, similar to be known as the optimal temperature for their growth, and 25-35 psu, respectively. The minimal filtration rates of the clams were recorded at 5$^{\circ}C$ and 15 psu. At the similar temperature and salinity, the filtration rate of the younger clams was higher than that of the older ones. Thermal coefficient, Q$_{10}$ values at low temperature range were much higher than those at high temperature range. These results indicate the short-necked clam is more sensitive in cold water. As they grow up, they become more stronger against their ambient environmental changes, such as thermal-shock, salinity changes.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.3 no.3
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• pp.159-165
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• 2005

The characterization of radiological contamination inside pipes generated during the decommission of a nuclear facility is necessary before pipes can be recycled or disposed. But, existing direct measurements of radioactive contamination level using the survey-meter can not estimate the characteristic of contamination on a local area such as the pipe inside. Moreover, the measurement of surface contamination level using the indirect methods has many problems of an application because of the difficulty of collecting sample and contamination possibility of a worker when collecting sample. In this work, plastic scintillator was simulated by using Monte Carlo simulation method for detection of beta radiation emitted from internal surfaces of small diameter pipe. Simulation results predicted the optimum thickness and geometry of plastic scintillator at which energy absorption for beta radiation was maximized. In addition, the problem of scintillator processing and transferring the detector into the pipe inside was considered when fabricating the plastic detector on the basis of simulation results. The characteristic of detector fabricated was also estimated. As a result, it was confirmed that detector capability was suitable for the measurement of contamination level. Also, the development of a detector for estimating the radiological characteristic of contamination on a local area such as the pipe inside was proven to be feasible.

• Journal of Oral Medicine and Pain
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• v.21 no.1
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• pp.153-171
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• 1996

저수준레이저를 이용하여 창상이나 병소의 치유과정에 대한 효과를 조사하기 위하여 많은 연구가 시행되었다. 연구에 의하면 갈륨비소 레이저광이 생체자극효과를 가진다고 하며, 저수준레이저를 조사하면 단백질과 핵산 (DNA) 합성을 자극하여 치은섬유아세포의 증식을 촉진한다고 보고하였다. 외상병소나 근육병소의 치료에 사용된 레이저치료법에 관한 관심이 점증함에 따라 저수준레이저요법 (LLLI)의 치유효과를 설명하기 위하여 분자생물학적 수준의 연구를 시행하기에 이르렀다. 보고에 의하면 Mutans Streptococcide 는 LLLI를 사용시 증식이 촉진되며, 다른 세균에서도 유사한 증식효과가 나타날 것이라고 주장하였다. 그러므로 LLLI가 피부감염을 야기하는 가장 흔한 원인인 Staphylococcus aureus 도 마찬가지로 증식이 촉진되는 지를 조사해볼 필요가 있으며, 또한 감염과 같이 특정 병적 상태에서의 저수준레이저광의 효과는 아직까지 명확하게 밝혀져 있지 않았다. 그러므로 본 연구의 목적은 첫째, Staphyloc occus aureus 의 증식에 대한 저수준레이저광의 효과를 조사하는 실험이며, 둘째 Staphylococcus aureus 로 가염된 피부창상에 대한 저수준레이저광의 효과를 판정하는데 있다. 34개의 Staphylococcus aureus 배양표본을 사용하여 48시간의 세포주기동안 조사기간과 조사시간, 그리고 레이저 펄스(laser pulse)형에 따라 3가지 실험을 시행하여 증식에 가장 효과적인 상태와 가장 비효과적인 상태의 갈륨비소 반도체 레이저펄스를 결정하였다. 이후 지름 약 6 mm의 개방창상을 44마리 백서의 양측 대퇴부에 형성하여 모든 창상에 S. aureus를 감염시켰다. 모든 표본은 펄스형과 조사방법 (중앙조사법과 주변조사법)에 따르는 실험을 하기 위하여 4가지로 분류하였다. 각 백서의 양측 창상중 하나는 1,3,5,7일 마다 각 실험의 방법에 따라 레이저를 조사하고 실험동물의 다른 창상은 대조군으로서 사용하였다. 모든 창상의 면적은 실험 1,3,5,7 일째에 일정한 거리에서 사진촬영하여 면적계를 이용, 측정한 후 통계적인 의의를 조사하였다. 본 연구의 결과는 저수준레이저는 특정 조건하에서 S. aureus의 증식을 촉진하였다. 그러나 S. aureus에 감염된 창상을 저수준레이저로 조사시 치유가 촉진되었다. 중앙 조사법고 주변조사법에 의한 창상치유효과는 통계적인 의의가 보이지 않았다. 따라서 결론적으로 S. aureus 에 감염된 창상에 직접 또는 간접적이든 pulse의 종류에 관계없이 조사하는 경우 치유효과가 나타나는 것은 정사주위 조직의 LLLI 자극효과가 염증의 확산을 억제한다고 말할수 있다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.3
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• pp.732-737
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• 2016

Using the pyrolyzed carbon black (PCB) from waste tires, the performance of 13 mm dense-graded hot mix asphalt was evaluated. The Marshall mix design was carried out and the measured optimal asphalt content was 5.8%. The impact resonant test was conducted to obtain the elastic modulus and damping ratio of the hot mix asphalt. The elastic modulus of HMA increased with increasing amount of PCB. On the other hand, there was no significant change in the damping ratio. The Marshall mix design, indirect tensile test, permanent deformation test, and program analysis were carried out. The strength ratio of the PCB modified asphalt mixtures was within 10%. More 10% of PCB was not good for the permanent deformation of hot mix asphalt. From the pavement design program, the use of 5% PCB in hot mix asphalt showed a decrease in the top-down crack, bottom-up crack, and permanent deformation. Judging from the limited test and analysis, the use of 5% PCB is good for enhancing the pavement performance.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.320-320
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• 2023

강우 데이터는 수문기상, 환경, 농업, 자연재해, 그리고 수자원 시스템 분야에서 가장 필수적인 기본 요소 중 하나이다. 또한 강우 데이터는 수문학적 분석에서 활용되는 필수 입력 자료 중 하나로 관측 데이터의 품질에 따라 수문 모형을 이용한 모의 결과물의 정확도가 결정된다고 할 수 있다. 따라서, 강우 관측소별로 강우 데이터의 품질을 어떻게 관리하느냐에 따라 수문 모형의 활용 범위 및 수자원 관리의 효율성이 결정될 수 있다. 강우의 시공간적 변동성은 수 많은 인자들과 직간접적으로 연계되어 있기 때문에 미계측 강우 자료에 대해 직접 관측이 아닌 수치 모형을 이용하여 강우의 발생과 강우량을 산정하는 것은 매우 복잡한 과제 중 하나이다. 현재 국내에서 운용되고 있는 강우 관측소의 경우에도 미계측 된 강우 데이터가 존재함으로써 강우 데이터의 활용에 제한이 생기는 경우가 있다. 따라서, 이러한 미계측 데이터의 추정 및 보완은 보다 효과적인 수재해 방지, 수자원 관리를 위한 필수 과제 중 하나이다. 일반적으로, 미계측 강우를 산정하기 위해서 Kriging, Thiessen, 등우선법, 그리고 역거리 관측법 등 다양한 수문학적 방법들이 적용되고 있다. 이러한 방법들은 산악효과나 강우 관측소의 분포 상태 등을 고려하지 못하기 때문에 측정하는 지역에 따라 강우 추정 오차가 커질 수 있다는 한계가 있다. 최근에는 데이터 관측 시스템과 빅데이터 기술의 발전과 활용 가능한 데이터의 양이 증가함에 따라 머신러닝을 활용한 사례가 증가하고 있다. 머신러닝은 데이터 사이의 관계를 기반으로 분류, 회귀, 그리고 예측 문제에 주로 사용되는 기법 중 하나이다. 따라서, 본 연구에서는 광주광역시 지역에 위치한 주요 강우 관측 지점들을 대상으로 미계측 된 시강우 데이터를 추정 및 복원하고자 한다. 여기서 데이터 추정 기술이란 미계측 강우의 발생 유무 및 강우량을 추정할 수 있는 기술을 의미한다. 이를 위해 대표적인 머신러닝 알고리즘인 인공신경망(Artificial Neural Network) 및 랜덤포레스트(Random Forest)를 적용하였다.

• Journal of Conservation Science
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• v.31 no.3
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• pp.267-278
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• 2015

In this study, the elastomer cover, a new contact material, was developed to establish the customized ultrasonic measurement considering surface irregularities of stone cultural heritages. The cover exhibits high elastic force and wear resistance because it has tensile strength of 17MPa and elongation of 625%. In addition, as a result of comparative experiments for the seven types according to transducers and contact materials including the elastomer cover, rock surface irregularities significantly affect attenuation of ultrasonic velocity. The phenomenon was more noticeable in the chiseling finish and indirect transmission measurement rather than the dabbed finish and direct transmission measurement. However, the Type F using the exponential transducer and elastomer cover showed stable P-wave velocity and high amplitude regardless of the surface irregularities. This because the elastomer cover sufficiently sticks to surface irregularities and removes pores between a transducer and a rock specimen. Therefore, the Type F should be used for the ultrasonic measurement of stone cultural heritages with surface irregularities.

• Geophysics and Geophysical Exploration
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• v.6 no.1
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• pp.23-27
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• 2003

A magnetic survey on the lake war carried out to explore the possible UXO (unexploded ordnance) under the water. A magnetic gradiometer with 2 magnetometer sensors was used, which measures total magnetic intensity. For the positioning of the measurement points on the water, RTK (real time kinematic) survey system was used. The theoretical responses were calculated assumming the dimension and the material of the UXO so that the detectability could be investigated. Since the areal size of the survey vessel was rather small, the influence from the magnetic material of the vessel and the other equipments such as a laptop computer was not negligible, and the influence did not remain constant during the survey due to the change of survey direction. These effects were reduced remarkably using moving average technique. The result reveals the lineament of a pipe line laid on the bottom of the lake, which can be regarded as an indirect proof of detectability of the method.

• 한국HCI학회:학술대회논문집
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• 2008.02b
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• pp.126-130
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• 2008

It takes only few seconds to find an artifact that has anthropomorphic form. There are numerous examples illustrating human's shape in daily life products. Usage of anthropomorphic form has been a basic design strategy especially when industrial designers design intelligent service robots because most of robot features were basically from human. Therefore, it's necessary to use anthropomorphic form not only in appearance design but also in interaction design. To use anthropomorphic form effectively, it needs to measure how much the artifact is similar to human, and then to evaluate whether the usage of anthropomorphic form fits to the artifact. This study's goal was to set up an evaluation standard for anthropomorphism for robot design. We suggest that there are three criteria for the evaluation standard. Those are 'anthropomorphic form in appearance', 'anthropomorphic form in Human-Robot Interaction', and 'accordance in two former criteria'. We expect that when designers put an evaluation step of anthropomophism in their design process of robots, robots might become more preferred by users, and easier to understand how to interact with.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.3 s.55
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• pp.1-10
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• 2007

In general, the tension forces of hanger cable in suspension bridges play an important role in evaluating the bridge conditions. The vibration method, as a conventional one, has been widely applied to estimate the tension forces by using the measured frequencies on hanger cables. However, the vibration method is not applicable to short hanger cables because the fiequencies of short cables are severely sensitive to flexural rigidity. Thus, in this study, the tension forces of short hanger cables, of which the length is shorter than 10 meters, were estimated through back analysis of the cable fiequencies measured from Gwang-An suspension bridge in Korea. Direct approach to back analysis is adopted using the univariate method among the direct search methods as an optimization technique. The univariate method is able to search the optimal tension forces without regard to the initial ones and has a rapid convergence rate. To verify the feasibility of back analysis, the results from back analysis and vibration method are compared with the design tension forces. From the comparison, it can be inferred that back analysis results are more reasonable agreement with the design tension forces of short hanger cable. Therefore, it is concluded that back analysis applied in this study is an appropriate tool for estimating tension forces of short hanger cables.