• Nuclear Engineering and Technology
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• v.52 no.5
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• pp.984-994
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• 2020

It is reported that about 20% of accidents at nuclear power plants in Korea and abroad are caused by human error. One of the main factors contributing to human error is fatigue, so it is necessary to prevent human errors that may occur when the task is performed in an improper state by grasping the status of the operator in advance. In this study, we propose a method of evaluating operator's fitness-for-duty (FFD) using various parameters including eye movement data, subjective fatigue ratings, and operator's performance. Parameters for evaluating FFD were selected through a literature survey. We performed experiments that test subjects who felt various levels of fatigue monitor information of indicators and diagnose a system malfunction. In order to find meaningful characteristics in measured data consisting of various parameters, hierarchical clustering analysis, an unsupervised machine-learning technique, is used. The characteristics of each cluster were analyzed; fitness-for-duty of each cluster was evaluated. The appropriateness of the number of clusters obtained through clustering analysis was evaluated using both the Elbow and Silhouette methods. Finally, it was statistically shown that the suggested methodology for evaluating FFD does not generate additional fatigue in subjects. Relevance to industry: The methodology for evaluating an operator's fitness for duty in advance is proposed, and it can prevent human errors that might be caused by inappropriate condition in nuclear industries.

• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4291-4296
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• 2011

Gravitational SPLITT fractionation (GSF) provides separation of colloidal particles into two subpopulations in a preparative scale. Conventionally, GSF is carried out in a thin rectangular channel having two inlets and two outlets at the top and bottom of the channel, respectively. And the channel is equipped with two flow-splitters, one between the top and bottom inlets and another between the top and bottom outlets. A large scale splitter-less GSF system had been developed, which was designed to operate in the full feed depletion (FFD) mode. In the FFD mode, there is only one inlet through which the sample is fed, thus preventing the sample dilution. In this study, the effect of the sample-loading (in the unit of g/hr) on the fractionation efficiency (FE, number% of particles in a GSF fraction that have the sizes expected by theory) of the new large scale splitter-less FFD-GSF system was investigated. The system was tested in the sample-loading range of 3.0-12.0 g/hr with polyurethane latex beads (PU) and sea-sediment. It was found that there is an optimum range in the sample-loading for a FFD-GSF separation. It was also found that there is a general tendency of FE decreasing as the concentration of the sample suspension increases.

• Analytical Science and Technology
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• v.28 no.6
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• pp.453-459
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• 2015

Split-flow thin cell fractionation (SPLITT fractionation, SF) is a particle separation technique that allows continuous (and thus a preparative scale) separation into two subpopulations based on the particle size or the density. In SF, there are two basic performance parameters. One is the throughput (TP), which was defined as the amount of sample that can be processed in a unit time period. Another is the fractionation efficiency (FE), which was defined as the number % of particles that have the size predicted by theory. Full-feed depletion mode (FFD-SF) have only one inlet for the sample feed, and the channel is equipped with a flow stream splitter only at the outlet in SF mode. In conventional FFD-mode, it was difficult to extend channel due to splitter in channel. So, we use large scale splitter-less FFD-SF to increase TP from increase channel scale. In this study, a FFD-SF channel was developed for a large-scale fractionation, which has no flow stream splitters (‘splitter less’), and then was tested for optimum TP and FE by varying the sample concentration and the flow rates at the inlet and outlet of the channel. Polyurethane (PU) latex beads having two different size distribution (about 3~7 µm, and about 2~30 µm) were used for the test. The sample concentration was varied from 0.2 to 0.8% (wt/vol). The channel flow rate was varied from 70, 100, 120 and 160 mL/min. The fractionated particles were monitored by optical microscopy (OM). The sample recovery was determined by collecting the particles on a 0.1 µm membrane filter. Accumulation of relatively large micron sized particles in channel could be prevented by feeding carrier liquid. It was found that, in order to achieve effective TP, the concentration of sample should be at higher than 0.4%.

• Bulletin of the Korean Mathematical Society
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• v.41 no.3
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• pp.473-482
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• 2004

Let D be an integral domain, I a proper ideal of D, and R =D[It, $t^{-1}$] a generalized Rees ring, where t is an indeterminate. For suitable conditions, we show that R satisfies the ACCP (resp., is a BFD, an FFD, a (pre-) Schreier domain, a G-GCD domain, a PVMD, a v-domain) if and only if D satisfies the ACCP (resp., is a BFD, an FFD, a (pre-) Schreier domain, a G-GCD domain, a PVMD, a v-domain).

• Proceedings of the Safety Management and Science Conference
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• 2009.04a
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• pp.423-427
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• 2009

This study proposes the generation mechanism of various design matrix using generalized linear model for design of experiment. Design generation method of GLM analysis, factorial design(FD) with center points, ANOVA design with lack-of-fit test, and response surface design are introduced. In central composite(CC) design, orthogonal blocking and fractional factorial design(FFD) are presented. We compare the design of Box-Benhken(BB) and face-centred central compsite design.

• Korean Journal of Computational Design and Engineering
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• v.9 no.1
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• pp.44-50
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• 2004

Mechanical parts are often grouped into part families based on the similarity of their shapes, to support efficient manufacturing process planning and design modification. The 2-part sequence papers present similarity assessment techniques to support part family classification for machined parts. These exploit the multiple feature decompositions obtained by the feature recognition method using convex decomposition. Convex decomposition provides a hierarchical volumetric representation of a part, organized in an outside-in hierarchy. It provides local accessibility directions, which supports abstract and qualitative similarity assessment. It is converted to a Form Feature Decomposition (FFD), which represents a part using form features intrinsic to the shape of the part. This supports abstract and qualitative similarity assessment using positive feature volumes. FFD is converted to Negative Feature Decomposition (NFD), which represents a part as a base component and negative machining features. This supports a detailed, quantitative similarity assessment technique that measures the similarity between machined parts and associated machining processes implied by two parts' NFDs. Features of the NFD are organized into branch groups to capture the NFD hierarchy and feature interrelations. Branch groups of two parts' NFDs are matched to obtain pairs, and then features within each pair of branch groups are compared, exploiting feature type, size, machining direction, and other information relevant to machining processes. This paper, the first one of the two companion papers, describes the similarity assessment methods using convex decomposition and FFD.

• Bulletin of the Korean Chemical Society
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• v.32 no.2
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• pp.681-686
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• 2011

SPLITT Fractionation (SF) provides separation of sample into two subpopulations. Separation into more than two subpopulations requires repeated SF operations. In this study, two Gravitation SF (GSF) channels were connected in a series (Tandem GSF) to obtain a separation into three subpopulations and to improve the fractionation efficiency (FE) of the fraction-b in the full-feed depletion (FFD) mode. In a single channel FFD-GSF operation, the fraction-a contained mostly the beads smaller than the cutoff diameter ($d_c$), while the fraction-b contained beads smaller than $d_c$ as well as those larger than dc, as expected. The measured FE's of the fraction-b are much lower than those of the fraction-a in all cases. The FE's of the fraction-a are higher than 84% with the average of about 91%, while those of the fraction-b are lower than 60% with the average of about 43%. No particular trends were found between FE and $d_c$, indicating the performance of FFD-GSF does not change with $d_c$ in the range where tested. Also no clear trends were observed between the FE and the sample-feeding flow rate, indicating higher sample-feeding rate can be used to increase the sample throughput without losing resolution. When two GSF channels were connected so that the flow stream emerging from the outlet-b of the channel-1 is fed directly into the channel-2, all three FE's measured for the fraction-1a were high with the average value of 99%, indicating it contains almost purely the beads smaller than $d_c$. The FE's measured for the fraction-2a are still good with the average value of 92%. The FE's measured for the fraction-2b are 64% in average, which is about 20% improvement from those obtained in a single channel FFD-GSF at the same conditions.

• Journal of radiological science and technology
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• v.21 no.1
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• pp.52-58
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• 1998

We can and must improve the diagnostic images using available knowledge and technology. At the same time we must strive to reduce the patient's integral and entrance radiation dose. Reducing the integral dose to the patient during the radiologic procedure is a primary concern of the patient, especially the pediatric patient, the radiologist and the technologist. A 100cm focal film distance generally is used for most over-table radiography. The early x-ray tubes and screen film combinations required long exposures, which often resulted in motion artifacts. But nowaday, we have the generators and x-ray tubes that can deliver the energy necessary in a very short time and the receptors that can record the information just as rapidly. And, we performed this studies to evaluate the patient exposure dose and the image quality by increasing focal film distance in diagnostic radiography. There are many factors which affected to exposure factor, but we studied to verify of FFD increase, only. Effect of increasing the focal film distance to a 140 cm distance was tested as follows; 1. The focal film distances were set at 100, 120, and 140cm. 2. A 18cm acryl(tissue equivalent) phantom was placed on the table top. 3. An Capintec 192 electrometer with PM 05 ion chamber was placed at the entrance surface of the phantom, and exposure were made at each focal film distances. 4. The procedure was repeated in the same manner as above except the ion chamber was placed beneath the phantom at the film plane. 5. Exit exposure were normalize to 8mR for each portions of the experiment. Based on the success of the empirical measurements, a detailed mathematical analysis of the dose reduction was performed using the percent depth dose data. The results of this study can be summerized as followings ; 1) Increasing FFD from 100 cm to 140 cm, we would create a situation that would have a significant effect on the overall quality of radiograph and achive the 17.42% reduction of entrance dose and the 18.95% reduction of integral dose that the patient receives. 2) Thickness of Al step wedge for equal film density increased with the long distance. 3) Increasing FFD, Magnification of image was lowered. 4) Resolution of image also increased with the FFD. As the results described above, we strongly recommend using the long FFD to provide better information for our patients and profession in abdomen radiographic studies.

• Journal of Environmental Impact Assessment
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• v.32 no.1
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• pp.49-59
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• 2023

The rapid advance of technology has accelerated global warming. As 50.4 percent of South Korea's population is concentrated in the Seoul Metropolitan Area, which has become a considerable emitter of greenhouse gases, the city's average temperature is expected to increase more rapidly than in other areas in the country. A rise in the average temperature would affect everyday life and urban ecology; thus, appropriate measures to cope with the forthcoming disaster are in need. This study analyzed the changes in plant phenological phases from the past to the present based on temperatures (average temperature of Feb, Mar, April) observed in seven different weather stations nearthe Seoul Metropolitan Area (Ganghwa, Seoul, Suwon, Yangpyeong, Icheon, Incheon, and Paju) and the first flowering dates of Plum tree (Prunus mume), Korean forsythia (Forsythia koreana), Korean rosebay (Rhododendron mucronulatum), Cherry tree (Prunus serrulate), Peach tree (Prunus persica), and Pear tree (Pyrus serotina). Then, RCP (Representative Concentration Pathways) 2.6 and 8.5 scenarios were used to predict the future temperature in the Seoul Metropolitan Area and how it will affect plant phenological phases. Furthermore, the study examined the differences in the flowering dates depending on various strategies to mitigate greenhouse gases. The result showed that the rate of plant phenological change had been accelerated since the 1900s.If emission levels remain unchanged, plants will flower from 18 to 29 earlier than they do now in the Seoul Metropolitan Area, which would be faster than in other areas in the country. This is because the FFD (First Flowering Date), is highly related to temperature changes. The Seoul Metropolitan Area, which has been urbanized more rapidly than any other areas, is predicted to become a temperature warming, forcing the FFDs of the area to occur faster than in the rest of the country. Changes in phenology can lead to ecosystem disruption by causing mismatches in species interacting with each otherin an ecosystem. Therefore, it is necessary to establish strategies against temperature warming and FFD change due to urbanization.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.5
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• pp.729-737
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• 2009

This paper introduces the machine tools feed system, which can be optimized the control's performance through simulation and the adjustment of the mechanical components. One method simulates the frequency response of the speed-loop with the design value using the MATLAB application, so that all of the interpolation axis can be equal to the response bandwidth, resulting in a high accuracy rate. The other method sees the mechanical component being adjusted by analyzing the results of various experiments. Lastly, this client's program is able to change the parameters that are related to the FFD, as well as the parameters in the friction compensation of the OPEN-CNC.