• Journal of Korean Society for Geospatial Information Science
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• v.3 no.1 s.5
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• pp.123-137
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• 1995

The digital information of Land is very important as the basis of geo-spatial information system. And the necessity of it is also increasing. But these days, every other institute that is needing digital map is seperately digitalizing lsnd information. So we need the stadard of accuracy evaluation and the method of hypothesis test for it. In this study, we check the standards of foreign countries and compare and analyze with our country's. After doing it, we suggest the direction for standard of digital map and statistical methods for testing accuracy evaluation about total maps that is digitized. Using hypergeometric distribution for considering consumer risk and producer risk, the statistical test can be for deciding optimal sampling map numbers by the total map and the agreement of contacting parties.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.3
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• pp.176-183
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• 2015

This research proposes a method to estimate the fatigue life of SSD(solid-state drive) due to the effect of dummy solder ball under forced vibration. A finite element model of the SSD was developed to simulate the forced vibration and a modal testing was performed to verify the developed finite element model. Fatigue life of the SSD under vibration was experimentally determined according to JEDEC standard in which the SSD was excited by a sinusoidal sweep vibration within the narrow frequency band around the first natural frequency until the SSD fails. Basquin's equation was introduced to estimate the fatigue life of the SSD due to the effect of dummy solder balls. It shows that the dummy solder balls are effective elements of the SSD to increase the fatigue life of an SSD by increasing 700 times of the fatigue life of the given SSD.

• Journal of the Korean Society of Safety
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• v.27 no.5
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• pp.30-34
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• 2012

A safety helmet is a personal protective equipment to protect the head from falling and flying objects. A safety helmet has the maximum delivered impact force as shock absorption performance, the lower delivered impact force the better performance, which was not a controlled variety during manufacturing safety helmet. Accordingly there were some difficulties in establishing the standard for improved performance as there was not a clear controllable impact force for improved performance. In this study the shock absorption performance was intended to be found as coefficient of restitution related to impulse. As a research method, a coefficient of restitution during the absorption of shock was calculated using the impulse transferred to pharynx utilizing the safety helmet shock absorption performance testing device based on the theory of momentum and impulse. The estimated impulsive force curve was derived assuming that shock was not absorbed using the measured data. The sample was selected as tested goods of ABS material for safety certification available mainly in the market. As a result of study, the maximum delivered impact force of safety helmet made by a domestic safety certified a company was 735 N, and its coefficient of restitution proved to be 0.64. The smaller coefficient of restitution is, the lower maximum delivered impact force and the higher shock absorption performance. The coefficient of restitution can be used as a performance index of safety helmet.

• Steel and Composite Structures
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• v.15 no.6
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• pp.659-677
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• 2013

This paper introduces new specimens of Steel-Carbon Fibre Reinforced Polymer composite developed in accordance with standard test method and definition for mechanical testing of steel (ASTM-A370). The main purpose of this research is to study the behaviour of steel-CFRP composite specimen under uniaxial tension to use it in beams in lieu of traditional steel bar reinforcement. Eighteen specimens were prepared and divided into six groups, depending upon the number of the layers of CFRP. Uniaxial tensile tests were conducted to determine yield strength and ultimate strength of specimens. Test results showed that the stress-strain curve of the composite specimen was bilinear prior to the fracture of CFRP laminate. The tested composite specimens displayed a large difference in strength with remarkable ductility. The ultimate load for Steel-Carbon Fibre Reinforced Polymer composite specimens was found using the model proposed by Wu et al. (2010) and nonlinear FE analysis. The ultimate loads obtained from FE analysis are found to be in good agreement with experimental ones. However, ultimate loads obtained applying Wu model are significantly different from experimental/FE ones. This suggested modification of Wu model. Modified Wu's model which gives a better estimate for the ultimate load of Steel-Carbon Fibre Reinforced Polymer (SCFRP) composite specimen is presented in this paper.

• Journal of The Korean Society of Agricultural Engineers
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• v.49 no.3
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• pp.21-31
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• 2007

This study is aimed at the development of a runoff forecasting model by using the Fuzzy inference system and Neural Network model to solve the uncertainties occurring in the process of rainfall-runoff modeling and improve the modeling accuracy of the stream runoff forecasting. The Neuro-Fuzzy (NF) model were used in this study. The NF model, recently received a great deal of attention, improve the existing Neural Networks by the aid of the Fuzzy theory applied to each node. The study area is the downstreams of Naeseung-chun. Therefore, time-dependent data was obtained from the Wolpo water level gauging station. 11 and 2 out of total 13 flood events were selected for the training and testing set of model respectively. The schematic diagram method and the statistical analysis are conducted to evaluate the feasibility of rainfall-runoff modeling. The model accuracy was rapidly decreased as the forecasting time became longer. The NF model can give accurate runoff forecasts up to 4 hours ahead in standard above the Determination coefficient $(R^2)$ 0.7. In the comparison of the runoff forecasting using the NF and TANK models, characteristics of peak runoff in the TANK model was higher than ones in the NF models, but peak values of hydrograph in the NF models were similar.

• Microbiology and Biotechnology Letters
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• v.34 no.4
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• pp.357-362
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• 2006

A growth inhibition assay using Chlorella sp. AG 10002 based on the OECD 201 standard test procedure was applied to the toxicity testing of endosulfan and its reported metabolites. Comparison of dry cell weight, optical density (OD) at 680 nm, and chlorophyll a concentration indicated that optical density at 680 nm of culture broth is convenient, rapid, and accurate method for cell growth. In this microalgae system, the $IC_{50}$ values of endosulfan, endosulfan sulfate, endosulfan lactone, and endosulfan ether were determined as 9.45, 18.8, 18.2 and 37.5 mg/L, respectively. In a while, endosulfan diol did not show a significant toxicity up to 50 mg/L. Since endosulfan is liable at acidic or alkaline conditions, treatment of endosulfan in pH 3, 4, and 11 for 3 days resulted in reduced toxicity, as expected. These results suggested that the microalgae system is useful to evaluate various toxic chemicals and provide a new notion for bioremediation of endosulfan in aqueous systems.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.668-674
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• 2002

Structural integrity assessment is indispensable for preventing catastrophic failure of industrial structures/components/facilities. This diagnosis of operating components should be done periodically for safe maintenance and economical repair. However, conventional standard methods for mechanical properties have the problems of bulky specimen, destructive and complex procedure of specimen sampling. Especially, the mechanical properties at welded zone including weldment and heat affected zone could not be evaluated individually due to their size requirement problem. So, an advanced indentation technique has been developed as a potential method for non-destructive testing of in-field structures. This technique measures indentation load-depth curve during indentation and analyzes the mechanical properties related to deformation such as yield strength, tensile strength and work-hardening index. Also indentation technique can evaluate a residual stress based on the concept that indentation load-depth curves were shifted with the direction and the magnitude of residual stress applied to materials. In this study, we characterized the tensile properties and welding residual stress of various industrial facilities through the new techniques, and the results are introduced and discussed.

• Journal of the Microelectronics and Packaging Society
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• v.18 no.2
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• pp.35-41
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• 2011

Recently, board level solder joint reliability performance of IC packages during drop impact becomes a great concern to semiconductor and electronic product manufacturers. The handheld electronic products are prone to being dropped during their useful service life because of their size and weight. The IC packages are susceptible to solder joint failures, induced by a combination of printed circuit board (PCB) bending and mechanical shock during impact. The board level drop testing is an effective method to characterize the solder joint reliability performance of miniature handheld products. In this paper, applying the JEDEC (JESD22-B111) standard present a finite element modeling of the FBGA. The simulation results revealed that maximum stress was located at the outermost solder ball in the PCB or IC package side, which consisted well with the location of crack initiation observed in the failure analysis after drop reliability tests.

• Journal of Environmental Health Sciences
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• v.37 no.1
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• pp.57-63
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• 2011

Crocidolite quality control (QC) sampling created by the wet generation method has been validated by validation tests such as the accuracy, precision, and storage tests. For this study we designed and developed a manufacturing apparatus and standard operating procedure for making these QC samples. The most important step in the procedure of making QC samples was the stage eliminating static electricity in asbestos fibers. This static electricity hampers the fibers clog functioning. In accuracy and precision tests by phase contrast microscopy analysis, the difference between the reference values and the studied values was at maximum 17.8%. This satisfies the AIHA proficiency analytical test criteria for asbestos. We could confirm the nearly even distribution of crocidolite fibers on the membrane filter. Also, there was no loss of fibers in the storage test after the one month.

• Journal of Environmental Health Sciences
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• v.40 no.2
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• pp.81-87
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• 2014

Objectives: We measured the concentrations of culturable airborne fungi (CAF) in enclosed environments at 16 underground subway stations of the Seoul Metro in 2013, and investigated the effect of environmental factors, including temperature, relative humidity, the number of passengers, and distance from the platform. Methods: The cultured fungi were identified by the lactophenol cotton blue (LPCB) staining method and were classified by observing the form, shape, and color of colony. A nonparametric analysis was used to determine if the differences in the concentrations of CAF were statistically significant. Results: The concentrations of CAF at the stations were the highest in station p ($367CFU/m^3$) with arange between 3 and $437CFU/m^3$. There was a significant correlation between CAF concentration and the distance from platform (r = 0.544, p < 0.01). Geotrichum spp. and Penicillium spp. were the predominant species. Conclusion: It is recommended that special attention be given during rush hour, which is in the morning (08:00-10:00) and in the early evening (18:00-19:00) to improve the indoor air quality of the subway stations.