• Journal of Ocean Engineering and Technology
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• v.10 no.2
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• pp.77-87
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• 1996

The estimation of the remaining life for the aged components in power plant as well as chemical and peroleum plants has been recently coberned. The raw materials used in this syudy are the 1Cr-1Mo-0.25V rotor steel which intensified P and S compositions along with the nominal compositions of ASTM A470 standard. Five kinds of specimens with the different degradation levels were prepared by isothermal aging teat treatment at $630^{\circ}C$ The mechanical properties and fatigue strength of virgin and aged 1Cr-1Mo-0.25V rotor steel have been inbestigated through the hardness, tensile, fatigue test, SEM fractograph and EDS analysis at room temperature. Thus, the data of aged specimens were compared with those of virgin specimen to evaluate the aging effects. The main results obtained in this study are as follows; The decrease of the hardness due to degradation was distinguished until 50, 000hrs simulated service time. And is was confirmed that the considerable amount of P, Mn, Cr and S was precipitated at the grain boundary of aged material through the SEM and EDS analysis. The fatigue strength of 25, 000, 50, 000, 75, 000 and 100, 000hrs aged material was decreased 29.5%, 24.4%, 28.6%, 35.7% than that of virgin material at $10^7$ cycles of room temperature. The major cracks of virgin and aged materials initiated at the inclusions including Si, P and Mn compositions which were located at the outer periphery of the specimen.

• The Transactions of the Korea Information Processing Society
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• v.4 no.2
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• pp.409-429
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• 1997

Problems encountered during software development or pteration nay result from defects in the software,ghrdware,or their oterations.Because of their diversity,the determination of the sources of a problem and its corrective adtion requires a centrally controlled system for monitoring provlems and detemining systematiccauses. In the paper,the SPR/SCR management system was developed and applied for the collection and analysis of the error data,process data and product data delected by each phasd in SDLC.There are four objectibes in the SPR/SCR management system.The first is to assure that software errors are documented,corrected,and vot forgottem. The second is to assure that SPR.are assessed for their validity.The third is to provide feedback on SPR status to the developer and the user.The fourth is ot prvide data for measuring and prediciting sofware quality and reliability.These goals could be satisfied by the application of the SPR/SCR mangement system.Also,the accomplishment rate of software reliability,criterion of test completion,estimation of release time, efficient development and management can be reflected by applying the SPR/SCR management system.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.6
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• pp.1479-1485
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• 2012

The parking management system can increase driver's convenience with detailed parking information service in the parking lot. At the same time, parking management system consumes non-negligible electrical energy with large amount of sensors, displays and control modules. With the increase in the demand for green and sustainable building design all over the world, it becomes a meaningful issue for parking management system to reduce operating power. This paper presents the preliminary design and estimated results of a parking management system which is optimized to reduce the power consumption mainly on detectors and displays. The system design is based on pre-developed wireless parking detectors, Park Tile and Park Disk. The system has a number of parking space detectors, vehicle count detectors, information displays, guidance terminals and other control units. We have performed system architecture design, communication network design, parking information service scenario planning, battery life regulation and at last operating power estimation. The estimated operating power was 0.93KW per parking-slot, which is 20% of traditional systems. The estimated annual maintenance cost was 18% of traditional systems.

• Journal of Environmental Health Sciences
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• v.34 no.4
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• pp.316-326
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• 2008

The Earth's temperature has risen $0.76^{\circ}C$ (degree) during last 100 years which Implies a sudden rise, compare with the 4oC (degrees) rise through out the past 20,000 years. If the volume of GHG (Greenhouse Gas) emission continues at the current level, the average temperature of the Earth will rise by $1^{\circ}C$ (degree) by 2030 with the further implication that the temperature of Earth will rise by $2{\sim}5^{\circ}C$ (degrees) every 100 years. Therefore, as we are aware that the temperature of the glacial epoch was $8{\sim}9^{\circ}C$ (degrees) lower than the present time, we can easily predict that the above temperature rises can be potentially disastrous for human life. Every country in the world recognizes theseriousness of the current climate change and adopted a convention on climate change in June 1992 in Rio. The COP1 was held in March 1995 in Berlin and the COP3 in Dec. 1997 in Kyotowhere the target (2008-2012) was determined and the advanced nations' reduction target (5.2%, average)was also agreed at this conference. Korea participated in the GHG reduction plan which required the world's nations to ratify the Kyoto Protocol. Ratification of the Kyotoprotocol and the followup requirement to introduce an international emissions trading scheme will require severe reductions in GHGs and considerable economic consequences. USA are still refusing to fully ratify the treaty as the emission reductions could severely damage the economies of these countries. In order to estimate the exact $CO_2$ emission, this study statistically analyzed $CO_2$ emission of each country based on the following variables : level of economic power and scientific development, the industrial system, productivity and energy efficiency.

• Journal of the Korean Data and Information Science Society
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• v.25 no.6
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• pp.1315-1331
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• 2014

Replacement rates which shows the ratio of retirement income relative to preretirement income is used for a valuable evaluation measures while discussing social security benefit levels or the adequacy of retirement income. However, replacement rates has been only used for an index for evaluating benefit level at the time of retirement or specific retirement period in advanced research projects. This article analyzes how much the uncertainty of survival has an influence on retirement income, and shows replacement rates in conformity with the period of survival as an index. The researchers named this index lifetime income replacement rates. Analysis based on this index shows both life replacement income rates of 38.3% in men's case and of 41.1% in women's case while enrolled for 20years in three pension plans - national pension, retirement pension and individual annuity.

• Fire Science and Engineering
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• v.33 no.2
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• pp.85-97
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• 2019

Today, building constructions are becoming larger, higher, deeper, and complex to improve quality of human life and meet various needs. As a result, new design space for non - typically standardized space has been created, and targets for performance-based design are also becoming increased. An evacuation safety evaluation of performance-based design should be compared with ASET and RSET estimation so that the value of RSET does not exceed the value of ASET. However, there is a problem that it is difficult to secure the safety with using the performance-based design evaluation method currently in use, especially in case of the underground parking lot, because it has wide compartment area and various routes for evacuation. Therefore, in order to overcome these problems, this paper first investigates the simulation setting method of the performance-based design that is currently in use, and then conducts two fire simulations and three evacuation simulations for underground parking lots each time, so performs the evacuation safety evaluationin total six cases of situations. Here this paper analyzes the problem with comparative evaluation research and suggests the better solution for improved evacuation safety evaluation of performance-based design.

• Journal of Radiation Protection and Research
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• v.46 no.4
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• pp.178-183
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• 2021

Background: This study was carried out to provide environmental transfer parameter values to estimate activity concentrations of these radionuclides in agricultural crops when direct contamination occurred. Materials and Methods: Mass interception fractions (F_Bs) and weathering half-lives (T_ws) of ¹³¹I and radiocesium were calculated using openly available monitoring data obtained after the Fukushima Daiichi Nuclear Power Plant accident. F_B is the ratio between the initial radioactivity concentration of a radionuclide retained by the edible part of the plant (Bq·kg^-1 fresh weight [FW]) and the amount of deposited radionuclide in that area (Bq·m^-2). T_w values can be calculated using activity concentrations of crops decreased with time after the initial contamination. Results and Discussion: Calculated F_B and T_w values for ¹³¹I and radiocesium were mostly obtained for leafy vegetables. The analytical results showed that there was no difference of F_Bs between ¹³¹I and radiocesium by t-test; geometric mean values for leafy vegetables cultivated under outdoor conditions were 0.058 and 0.12 m²·kg^-1 FW, respectively. Geometric mean T_w value of ¹³¹I in leafy vegetables grown under outdoor conditions was 8.6 days, and that of radiocesium was 6.6 days; there was no significant difference between T_w values of these radionuclides by Wilcoxon rank sum test. Conclusion: There was no difference between ¹³¹I and radiocesium for F_Bs and T_ws. By using these factors, we would be able to carry out a rough estimation of the activity concentrations of ¹³¹I and radiocesium in the edible part of leafy crops when a nuclear accident occurred.

• Journal of the Korean Wood Science and Technology
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• v.31 no.2
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• pp.84-91
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• 2003

In this study, the three species (Populus euramericana, Pinus densiflora and Quercus variabilis) were cut to difference (0, 0.15, 0.3, 0.45 mm) between the size of tip and that of root of the finger (DSTR) and jointed with poly vinyl acetate (PVA) and resorcinol-phenol resin (RPR). We described the relationship between the bending strength properties of finger DSTR and the acoustic emission (AE) generated during the bending test. The results were as follows: The AE generation time of finger-jointed specimens with RPR adhesive was earlier than that with PVA adhesive. The AE cumulative event count of finger-jointed specimens with RPR adhesive continuously increased with increasing load and the event count was much more than that with PVA adhesive. Also, the AE cumulative event count for resorcinol-phenol resin adhesive obtained from low load level was abundant. The AE wave in finger-jointed specimens with RPR adhesive could be detected in the below proportional limit load. Therefore, AE signals from bending test are useful for the estimation of strength in finger DSTR specimens.

• Journal of Korean Neurosurgical Society
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• v.66 no.4
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• pp.382-392
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• 2023

Objective : The use of indocyanine green videoangiography (ICG-VA) to assess blood flow in the brain during cerebrovascular surgery has been increasing. Clinical studies on ICG-VA have predominantly focused on qualitative analysis. However, quantitative analysis numerical modelling for time profiling enables a more accurate evaluation of blood flow kinetics. In this study, we established a multiple exponential modified Gaussian (multi-EMG) model for quantitative ICG-VA to understand accurately the status of cerebral hemodynamics. Methods : We obtained clinical data of cerebral blood flow acquired the quantitative analysis ICG-VA during cerebrovascular surgery. Varied asymmetric peak functions were compared to find the most matching function form with clinical data by using a nonlinear regression algorithm. To verify the result of the nonlinear regression, the mode function was applied to various types of data. Results : The proposed multi-EMG model is well fitted to the clinical data. Because the primary parameters-growth and decay rates, and peak center and heights-of the model are characteristics of model function, they provide accurate reference values for assessing cerebral hemodynamics in various conditions. In addition, the primary parameters can be estimated on the curves with partially missed data. The accuracy of the model estimation was verified by a repeated curve fitting method using manipulation of missing data. Conclusion : The multi-EMG model can possibly serve as a universal model for cerebral hemodynamics in a comparison with other asymmetric peak functions. According to the results, the model can be helpful for clinical research assessment of cerebrovascular hemodynamics in a clinical setting.

• Structural Engineering and Mechanics
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• v.90 no.1
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• pp.27-40
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• 2024

The prediction of VIV amplitude is essential for the design and fatigue life estimation of steel tubes in tubular transmission towers. Limited to costly and time-consuming traditional experimental and computational fluid dynamics (CFD) methods, a machine learning (ML)-based method is proposed to efficiently predict the VIV amplitude of steel tubes in transmission towers. Firstly, by introducing the first-order mode shape to the two-dimensional CFD method, a simplified response analysis method (SRAM) is presented to calculate the VIV amplitude of steel tubes in transmission towers, which enables to build a dataset for training ML models. Then, by taking mass ratio M^*, damping ratio ξ, and reduced velocity U^* as the input variables, a Kriging-based prediction method (KPM) is further proposed to estimate the VIV amplitude of steel tubes in transmission towers by combining the SRAM with the Kriging-based ML model. Finally, the feasibility and effectiveness of the proposed methods are demonstrated by using three full-scale steel tubes with C-shaped, Cross-shaped, and Flange-plate joints, respectively. The results show that the SRAM can reasonably calculate the VIV amplitude, in which the relative errors of VIV maximum amplitude in three examples are less than 6%. Meanwhile, the KPM can well predict the VIV amplitude of steel tubes in transmission towers within the studied range of M^*, ξ and U^*. Particularly, the KPM presents an excellent capability in estimating the VIV maximum amplitude by using the reduced damping parameter S_G.