• Progress in Medical Physics
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• v.18 no.1
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• pp.48-54
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• 2007

This study is to develope a phantom for MOSFET (Metal Oxide Semiconductors Field Effect Transistors) dosimetry and compare the dosimetric properties of standard MOSFET and microMOSFET with the phantom. In this study, the developed phantom have two shape: one is the shape of semi-sphere with 10cm diameters and the other one is the flat slab of $30{\times}30cm$with 1 cm thickness. The slab phantom was used for calibration and characterization measurements of reproducibility, linearity and dose rate dependency. The semi-sphere phantom was used for angular and directional dependence on the types of MOSFETs. The measurements were conducted under $10{\times}10cm^2$ fields at 100cm SSD with 6MV photon of Clinac (21EX, Varian, USA). For calibration and reproducibility, five standard MOSFETS and microMOSFETs were repeatedly Irradiated by 200cGy five times. The average calibration factor was a range of $1.09{\pm}0.01{\sim}1.12{\pm}0.02mV/cGy$ for standard MOSFETS and $2.81{\pm}0.03{\sim}2.85{\pm}0.04 mV/cGy$ for microMOSFETs. The response of reproducibility in the two types of MOSFETS was found to be maximum 2% variation. Dose linearity was evaluated In the range of 5 to 600 cGy and showed good linear response with $R^2$ value of 0.997 and 0.999. The dose rate dependence of standard MOSFET and microMOSFET was within 1% for 200 cGy from 100 to 500MU/min. For linearity, reproducibility and calibration factor, two types of MOSFETS showed similar results. On the other hand, the standard MOSFET and microMOSFET were found to be remarkable difference in angular and directional dependence. The measured angular dependence of standard MOSFET and microMOSFET was also found to be the variation of 13%, 10% and standard deviation of ${\pm}4.4%,\;{\pm}2.1%$. The directional dependence was found to be the variation of 5%, 2% and standard deviation of ${\pm}2.1%,\;{\pm}1.5%$. Therefore, dose verification of radiation therapy used multidirectional X-ray beam treatments allows for better the use of microMOSFET which has a reduced angular and directional dependence than that of standard MOSFET.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.5
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• pp.397-401
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• 2000

The corrosion-fatigue characteristics of the 12Cr steel, which is widely used in fossil power plants as a turbine blade material, are evaluated nondestructively by use of the Rayleigh surface wave. In this study, the frequency dependency of the Rayleigh surface wave is investigated indirectly by measuring the angular dependency of the backward radiation of the incident ultrasonic wave in the aged specimens, and then compared to the corrosion-fatigue characteristics. The width of the backward radiation profile decreases as the increase of the aging temperature, which seems to result from the increase of the effective degrading layer thickness. This parameter also shows an inversely proportionality to the exponent, m, in the Paris law which predicts the crack size increasement due to fatigue. The result observed in this study demonstrates high potential of the backward radiated ultrasound as a tool for the nondestructive evaluation of the corrosion-fatigue characteristics of the aged materials.

• Geotechnical Engineering
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• v.11 no.4
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• pp.99-110
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• 1995

In this study, friction angles on the surface of vertical rigid ground anchor in normally consolidated dry sand were measured by model pullout tests in laboratory. Friction angles were obtained from the normal and shear stresses measured along depth of the anchor stir face by attaching several 2-dimensional load cells. Model tests were conducted under the plane strain state and axial symmetric state. From the results of tests, it was concluded that the maximum friction angle on the anchor surface coincides nearly with the maximum angle of stress obliquity on the plane of zero-extension direction obtained by plane strain compression test. This result was made with regard to the strength anisotropy and stress dependency of sand. It showed that when angle of shear resistance of the sand is applied to the friction angle of the anchor surface, the design capacity could be less than the applied force, thus making the anchor unsafe.

• Journal of The Korean Association For Science Education
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• v.26 no.3
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• pp.406-414
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• 2006

This study investigated 7th grade students' context dependency on explanations about propagating path of light in three different contextual problems: observation of an object, observation of an object's image in a mirror, and observation of one's own face reflection in a mirror. Researchers examined student response in each context through interviews. The students were classified into four groups according to their explanations for the three different contexts. Each group was redivided into two or three subgroups in accordance with their conceptual features. After that, researchers investigated the characteristics of each subgroup. Main findings of the study indicated that (1) group 1 students' conceptions differed in each context; (2) group 2 students showed scientific conceptions in C1 context but in C2 context they showed visual ray conceptions or image misconceptions; (3) group 3 students did not show scientific conceptions in C3 context by strong misconceptions about one's own face reflection in the mirror. Also, this paper discussed the educational implications of the results.

• The Korean Journal of Financial Management
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• v.20 no.2
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• pp.151-180
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• 2003

We examine the interdependence of the major Asia-Pacific stock markets including S&P 500, FTSE 100, Kualar Lumpur Composite, Straits Times, Hang Seng, NIKKEI 225 and KOSPI 200 from October 4, 1995 to March 31,2000. The analysis employs the vector-auto-regression, Granger causality, impulse response function and variance decomposition using daily returns on the national stock market indices. The findings in this paper indicate that the volatilities of all countries has grown after IMF crisis, while there is no significance in cointegration test of both total period and sub-periods. This result implies that investors are able to get abnormal returns by investment diversification according to the portfolio theory. We find that while the effect from NIKKEI 225 to others is relatively weak, the interdependence from S&P 500 to other countries is strong. Also we find that the strong effect from Straits Times to Hang Seng exists. This study suggests that there is slight feedback relation between KOSPI 200 and Kualar Lumpur Composite, Straits Times, Hang Seng stock market.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.1
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• pp.8-15
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• 2019

When RC(Reinforced Concrete) structures are exposed to harsh environment, deterioration phenomenon occurs, and the corrosion in rebar due to chloride intrusion is known as representative deterioration, so called chloride attack. In this paper, chloride resistance performance of 2 years aged concrete is evaluated considering 3 levels of water to binder ratio(0.37, 0.42, and 0.47) and 2 levels of substitution ratio of fly ash(0% and 30%). Accelerated chloride diffusion coefficient tests referred to Tang's method, total passed charge tests referred to ASTM C 1202, and compressive strength tests referred to KS F 2405 are performed. With adaptation of the previous test results and the results from this study, time-dependent chloride diffusion characteristics are analyzed for each concrete. The FA(Fly Ash) concrete has higher chloride resistance performance than OPC(Ordinary Portland Cement) concrete. According to the evaluation standard of ASTM C 1202, the FA concrete has "Moderate" grade after 49 days while OPC concrete does "Moderate" grade after 365 days. As the results of time-parameter for chloride diffusion, OPC concrete and FA concrete show the decreasing behavior of time-parameters with increasing water to binder ratio. Also, FA concrete has 1.57~2.74 times of time-parameter than OPC concrete. That's cause is thought that the time-parameter indicates the gradient of decreasing of diffusion coefficient. FA concrete has higher time-parameters than OPC concrete by pozzolanic reaction of FA.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.9
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• pp.5652-5659
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• 2014

The purpose of this study was to introduce a software task processing evaluation model that considers the following situations: i) a software system is integratedly composed of several number of modules, ii) each modules has its corresponding module task, iii) all module tasks are tested simultaneously, and iv) the processing times of the module tasks are mutually dependent. The software task completion probability with the module dependency was derived using the joint distribution function of Farlie [11]. The results showed that the task completion probability of software increases with increasing module dependency parameter.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5C
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• pp.255-262
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• 2008

In order to investigate the strength anisotropy of compacted materials, a series of unsaturated and saturated-drained triaxial compression tests was performed. Three different orientation angles of the axial direction of samples with respect to the horizontal plane were investigated: ${\delta}=0$, 45 and 90 degrees. As the results showed, the suction rate on the strength of the unsaturated specimen was not influenced by ${\delta}$. And the effect of the angle ${\delta}$ on the strength was more pronounced on unsaturated specimen as compared to saturated specimen. Moreover, a new procedure was proposed to take into account the effect of the angle ${\delta}$ on the shear strength of unsaturated soils.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.444-446
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• 2009

현재 대다수의 맥박(또는 심박) 측정 장치는 electrodes와 PPG로 국한되어 있다. 그러나 electrodes는 착용자의 불편감과 수입 의존성에 의한 높은 가격이라는 단점을 가지고 있으며, PPG는 동잡음에 약하다는 단점을 갖는다. 본 논문에서는 PPG와 flexible sensor를 동시 적용하여 상호 작용하게 함으로서 각 센서들의 단점을 보완 해줄 수 있는 하이브리드형의 맥박 측정 장치에 대하여 연구하였다.

• KIPS Transactions on Software and Data Engineering
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• v.8 no.3
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• pp.129-136
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• 2019

There are a variety of entities in natural language such as people, organizations, places, and products. These entities can have many various meanings. The ambiguity of entity is a very challenging task in the field of natural language processing. Entity Linking(EL) is the task of linking the entity in the text to the appropriate entity in the knowledge base. Pairwise based approach, which is a representative method for solving the EL, is a method of solving the EL by using the association between two entities in a sentence. This method considers only the interdependence between entities appearing in the same sentence, and thus has a limitation of global interdependence. In this paper, we developed an Entity2vec model that uses Word2vec based on knowledge base of RDF type in order to solve the EL. And we applied the algorithms using the generated model and ranked each entity. In this paper, to overcome the limitations of a pairwise approach, we devised a pairwise approach based on comprehensive interdependency and compared it.