• Journal of the Korean Society of Radiology
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• v.9 no.2
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• pp.121-124
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• 2015

Digital Mammography is very important for the early diagnosis of breast cancer. but excessive radiation dose to the patient may increase the probability of occurrence of breast cancer. absorbed dose rate and signal, noise, and contrast in accordance with the change of the filter, and analyzed the signal-to-noise ratio. absorbed dose rate GE Equipment is higher than that of Siemens and Hologic. using the material of Mo / Mo was lower than the other target-filter combination. SNR of Siemens equipment is high and measured high when Mo / Mo selected, the other two devices was measured high when Mo / Rh selected. when you choose a target-filter combination our results will be a good indicator.

• Journal of Korean Society on Water Environment
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• v.36 no.5
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• pp.453-467
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• 2020

This study aimed to inventory the water pollutant discharge of wastewater from two facilities, one primary steel manufacturing facility and one petroleum refinery, both of which are located in Korea, and to identify ways to improve the wastewater treatment process through field investigation. Probability evaluation was used to inventory the substances in polluted water. The samples collected in this study included original wastewater, on processing wastewater, and treated water. The general description of wastewater occurrence, major sources, and treatment facilities were also investigated to obtain an integrated database of the pollutants created by different industrial categories. Based on our analysis of raw wastewater and final effluent, the detected pollutants were confirmed by analyzing their presence in the raw or supplemental materials, the potential of formation as byproducts, and the possibility of inclusion as impurities. The compounds detected for each category were screened via investigation of their possible sources and confirmed as the final water pollutant inventories. Thirty kinds of water pollutants were emitted by the primary steel manufacturing facility (reference in case A), including 14 specified hazardous water pollutants. The petroleum refinery (reference in case B) emitted 36 water pollutants, including 16 specified hazardous water pollutants.

• Journal of the Korean Wood Science and Technology
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• v.28 no.1
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• pp.18-27
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• 2000

Even the same materials are assembled in flush door skin panel, warping is not simply prevented under the changes of environmental conditions since wood and wood-based material have large variations in their physical and mechanical properties. The parameters such as linear movement coefficient(LMC), modulus of elasticity (MOE), required to predict warping could be estimated by oven drying method and dynamic method instead of American Society for Testing Materials(ASTM) procedure. The relationship between warping and LMC was curvilinear, while it between warping and MOE was linear. LMC had a larger effect on warping than MOE. Material propensity of skin panel such as hardboard and plywood showed normal distributions. The variation of material properties, however, was much larger in plywood than in hardboard. Monte Carlo simulation also indicated that rejection ratio of flush door due to the occurrence of warping could be predicted with consideration of the relationship of warping and parameters of probability distribution of MOE, LMC, and moisture content.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2007.04a
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• pp.1-4
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• 2007

This study investigated the applicability of insulation curing method with double layer bubble sheets to the man concrete subjected to cold weather. Temperature history of the mass concrete indicated that the highest temperature of center section was exhibited at $34^{\circ}C$ while the that of surface section was $25^{\circ}C$. Difference between center and surface was shown to be less $10^{\circ}C$ when the temperature of center section was peak section, and thereby associated temperature cracking index was calculated 1.5, and occurrence probability of temperature cracking was 5%, so there was no temperature cracking caused by internal restraint. No temperature crack was observed by naked eye. It was clear that early frost demage and temperature cracking could be restrained due to reducing temperature difference between inner part and outside in the case double bubble sheets applied to insulation curing method in cold weather. The maturity of mass concrete is higher than outside about $72\sim89^{\circ}$ DD, so it was demonstrated to prevent early frost demage and ensure strength excellently. Insulation curing method with double bubble sheets was more economic than heating curing method.

• Journal of the Korea Institute of Building Construction
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• v.13 no.1
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• pp.75-83
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• 2013

The prevention of safety accidents can be achieved through Harvey's 3E's: Engineering, Enforcement, and Education. On construction sites, however, enforcement and engineering did not prove to be valid ways of reducing the number of safety accidents, as enforcement and engineering have failed to overcome and/or supplement the realistic limits regarding the relatively lower education levels of construction workers and the communication issues with foreign workers. On the other hand, safety education can enable the advancement of safety management by enhancing the educational contents and their methods of delivery. To improve the efficiency of safety education via educational contents, this research conducted a qualitative and quantitative analysis on the validity of the newly educational contents by overviewing possible accident types in different work phases. Of the accident types identified by the qualitative analysis, neither highly important nor insignificant accident types were found, yet all the suggested types are found to be required. In addition, this study did not find any significant differences in the occurrence probability of safety accidents related to the level of importance of each type of accident. The qualitative analysis in this research verified that the suggested accident types can be valid, educational material that can take into account future safety accidents.

• Korean Journal of Construction Engineering and Management
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• v.8 no.2
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• pp.68-74
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• 2007

It has been recognized that safety management is activated during the construction phase to prevent accidents and fatalities of workers. However, It is revealed that about 15% of fatal death accidents is caused by the lack of management of planning and design phases. There is a crucial need of assessing safety risk during building design phase. This paper is aimed to develop a safety risk assessment checklist that can be used during building design phase, utilizing the concept of Design for Safety. In doing so, a broad literature survey on safety management of building Process, various safety risk assessment toolboxes being utilized in the HSE and the BAA of UK. The proposed checklist contains the followings: 1) classification structure for safety design on space, element, and trade work 2) hazard risk factor, probability and degree of intensity of accident occurrence, and 3) safety assessment criteria. It is expected that the checklist would be an effective tool of preventing and minimizing fatal accidents of building construction projects.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.41 no.1
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• pp.50-58
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• 2018

Intermittent demand is a demand with a pattern in which zero demands occur frequently and non-zero demands occur sporadically. This type of demand mainly appears in spare parts with very low demand. Croston's method, which is an initiative intermittent demand forecasting method, estimates the average demand by separately estimating the size of non-zero demands and the interval between non-zero demands. Such smoothing type of forecasting methods can be suitable for mid-term or long-term demand forecasting because those provides the same demand forecasts during the forecasting horizon. However, the smoothing type of forecasting methods aims at short-term forecasting, so the estimated average forecast is a factor to decrease accuracy. In this paper, we propose a forecasting method to improve short-term accuracy by improving Croston's method for intermittent demand forecasting. The proposed forecasting method estimates both the non-zero demand size and the zero demands' interval separately, as in Croston's method, but the forecast at a future period adjusted by binomial weight according to occurrence probability. This serves to improve the accuracy of short-term forecasts. In this paper, we first prove the unbiasedness of the proposed method as an important attribute in forecasting. The performance of the proposed method is compared with those of five existing forecasting methods via eight evaluation criteria. The simulation results show that the proposed forecasting method is superior to other methods in terms of all evaluation criteria in short-term forecasting regardless of average size and dispersion parameter of demands. However, the larger the average demand size and dispersion are, that is, the closer to continuous demand, the less the performance gap with other forecasting methods.

• Journal of the Korean Society for Railway
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• v.12 no.5
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• pp.678-686
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• 2009

A trial run of locally-developed tilting train has been in process on Chungbuk line since the test vehicle was first produced. For the system stabilization, interface verification among the systems including track, structure, catenary and signaling system, not to mention the rolling stock, is very crucial. Therefore, in this study, the dynamic rail force of the tilting (Hanvit 200), high-speed (KTX) and general (Mugunghwa) vehicle caused by driving in transition curve track was measured. And, it compared the tilting response with the other by using the measured rail force data in transition curve track, and then evaluated probability the range of load fluctuation for the variable dynamic vertical and lateral wheel load. As a result, a range of rail force by occurred a change of cant from the high-speed and general vehicle which had fixed bogie structure was distributed throughout small deviation. Otherwise, in case of the tilting train which was consisted of the pendulum bogie structure was distributed wide range about large deviation by changed of cant.

• Journal of Korea Water Resources Association
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• v.46 no.8
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• pp.795-805
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• 2013

Drought is one of the severe natural disasters and it can profoundly affect our society and ecosystem. Also, it is a very important variable for water resources planning and management. Therefore, the drought is analyzed in this study to understand the drought distribution and trend. The Standard Precipitation Index (SPI) is estimated using precipitation data obtained from 55 rain gauge stations in South Korea and the SPI based drought variables such as drought duration and drought severity were defined. Drought occurrence and joint probabilistic analysis for SPI based drought variables were performed with run theory and copula functions. And then the return period and spatial distribution of droughts on the South Korea was estimated. As the results, we have shown that Gongju and Chungju in Chungcheong-do and Wonju, Inje, Jeongseon, Taebeak in Gangwon-do have vulnerability to droughts.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.37.2-37.2
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• 2009

In this study, we present a new empirical forecasting method of solar proton events based on flare parameters. For this we used NOAA solar energetic particle (SEP) events from 1976 to 2006 and their associated X-ray flare data. As a result, we found that about only 3.5% (1.9% for M-class and 21.3% for X-class) of the flares are associated with the proton events. It is also found that this fraction strongly depends on longitude; for example, the fraction for $30W^{\circ}$ < L < $90W^{\circ}$ is about three times larger than that for $30^{\circ}E$ < L < $90^{\circ}E$. The occurrence probability of solar proton events for flares with long duration (> 0.3 hours) is about 2 (X-class flare) to 7 (M-class flare) times larger than that for flares with short duration (< 0.3 hours). The relationship between X-ray flare peak flux and proton peak flux as well as its correlation coefficient are strongly dependent on longitude. Using these results for prediction of proton flux, we divided the data into 6 subgroups depending on two parameters: (1) 3 longitude ranges (east, center, and west) and (2) flare impulsive times (long and short). For each subgroup, we make a linear regression between the X-ray flare peak flux and the corresponding proton peak flux. The result shows that the proton flux in the eastern region is much better correlated with the X-ray flux than that in the western region.