• International Journal of Fluid Machinery and Systems
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• v.8 no.4
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• pp.254-263
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• 2015

The failure of hydraulic turbine runners is a rare event. So in order to assess the reliability of these components one cannot rely solely on the number of observed failures in a given population. However, as there is a limited number of degradation mechanisms involved, it is possible to use physically-based reliability models. Such models are often more complicated but are able to account for physical parameters in the degradation process. They can therefore help provide solutions to improve reliability. With such models, the effect of materials properties on runner reliability can be highlighted. This paper presents a brief review of the Kitagawa-Takahashi diagram which links the damage tolerance approach, based on fracture mechanics, to the stress or strain-life approaches. Using simplified response spectra based on runner stress measurements, we will show how fatigue reliability is sensitive to materials fatigue properties, namely fatigue crack propagation behaviour and fatigue limit obtained on S-N curves. Furthermore, we will review the influence of the main microstructural features observed in 13%Cr-4%Ni stainless steels commonly used for runner manufacturing. The goal is ultimately to identify the most influential microstructural features and to quantify their effect on fatigue reliability of runners.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.09a
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• pp.197-204
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• 2002

The resent earthquakes in worldwide have caused extensive damage to highway reinforced concrete bridge piers. It has been observed in the Korean Peninsula that the number of minor or low earthquake motions have increased year by year. Since the concern about the earthquake hazards is increased, the objective of this research is to evaluate the damage of reinforced concrete bridge piers subjected to probable earthquake motions. Experimental investigation was conducted to study the seismic performance of the full-scale specimens in size D=1.2m H=4.8m, which were constructed with different longitudinal lap splice and loading pattern, through the quasi-static test and the pseudo-dynamic test. It is thought that this result could contribute to establish the retrofit decision-making and disaster planning of reinforced concrete bridge piers in earthquake regions. And it could be also possible to quantify the damage of reinforced concrete bridge piers under cyclic loading

• Economic and Environmental Geology
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• v.28 no.4
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• pp.433-438
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• 1995

The most popular minimization method is based on the least-squares criterion, which uses the $L_2$ norm to quantify the misfit between observed and synthetic data. The solution of the least-squares problem is the maximum likelihood point of a probability density containing data with Gaussian uncertainties. The distribution of errors in the geophysical data is, however, seldom Gaussian. Using the $L_2$ norm, large and sparsely distributed errors adversely affect the solution, and the estimated model parameters may even be completely unphysical. On the other hand, the least-absolute-deviation optimization, which is based on the $L_1$ norm, has much more robust statistical properties in the presence of noise. The solution of the $L_1$ problem is the maximum likelihood point of a probability density containing data with longer-tailed errors than the Gaussian distribution. Thus, the $L_1$ norm gives more reliable estimates when a small number of large errors contaminate the data. The effect of outliers is further reduced by M-fitting method with Cauchy error criterion, which can be performed by iteratively reweighted least-squares method.

• Proceedings of the KACD Conference
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• 2003.11a
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• pp.552-552
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• 2003

The purpose of this study was to quantify the amount of remaining gutta-percha/sealer on the walls of root canals when three types of nickel-titanium rotary instruments and a hand instrument were used to remove these materials. Forty extracted mandibular premolars were prepared by step-back method and obturated with gutta-percha and sealer. Gutta-percha removal for group 1 was done using hand file with chloroform, group 2 using Profile and group 4 using K3. The following factors were evaluated : Time taken to reach working length, total time for gutta-percha removal and number of fractured instruments.(중략)

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.75.2-75.2
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• 2015

Extremely Red Objects (EROs) are characterized by their red optical-infrared colors (e.g., R-Ks > 5.0), which would be caused by either dusty star formation or old stellar population at moderate to high redshifts. We combine deep optical (Subaru R) and near-infrared (CFHT Ks) observations obtained as part of the Subaru $GTO2deg^2$ survey to select EROs over this field and to explore their properties. We present number densities of EROs as a function of magnitudes. We are planning to quantify the environments for EROs and to see if EROs reside in overdense regions.

• Journal of Communications and Networks
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• v.8 no.4
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• pp.442-450
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• 2006

Inter-operability between heterogeneous radio access technologies (RATs), in the sense of seamless vertical han-dover (VHO) support with common radio resource management (CRRM) functionalities, has recently attracted a significant research attention and has become a prominent issue in standardization fora. In this paper, we formulate the problem of load balancing between cooperative RAT's as a mathematical program and by trading off a pre-defined delay tolerance per request we propose a vertical handover batch processing (VHBP) scheme. To quantify the performance of the proposed VHBP scheme we compare it with a baseline processing scheme, where each VHO request is processed independently under a number of different network scenarios. Numerical investigations reveal significant net benefits of the proposed scheme compared with the baseline, both in terms of achieved load balancing levels but also with regard to the acceptance rate of the VHO requests.

• Architectural research
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• v.8 no.2
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• pp.27-36
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• 2006

Structural uncertainties are generally modeled using probabilistic approaches in order to quantify uncertainties in behaviors of structures. This uncertainty results from the uncertainties of structural parameters. Monte Carlo methods have been usually carried out for analyses of uncertainty problems where no analytical expression is available for the forward relationship between data and model parameters. In such cases any direct mathematical treatment is impossible, however the forward relation materializes itself as an algorithm allowing data to be calculated for any given model. This study addresses a new method which is utilized as a basis for the uncertainty estimates of structural responses. It applies double uniform random numbers (i.e. DURN technique) to conventional Monte Carlo algorithm. In DURN method, the scenarios of uncertainties are sequentially selected and executed in its simulation. Numerical examples demonstrate the beneficial effect that the technique can increase uncertainty degree of structural properties with maintaining structural stability and safety up to the limit point of a breakdown of structural systems.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.51-56
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• 2001

Vapor explosion is one of the most important problems encountered in severe accident management of nuclear power plants. In spite of many efforts, a lot of questions still remain for the fundamental understanding of vapor explosion phenomena. Therefore, KAERI launched a real material experiment called TROI using 20 kg of UO2 and ZrO2 to investigate the vapor explosion phenomena. In addition, a small-scale experiment with molten-tin/water system was performed to quantify the characteristics of vapor explosion and to understand the phenomenology of vapor explosion. A number of instruments were used to measure the physical change occurring during the vapor explosion. In this experiment, the vapor explosion generated by molten fuel water interaction is visualized using high speed camera and the pressure behavior accompanying the explosion is investigated.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.935-938
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• 2004

This paper describes the quantitative analysis on the improvement of equilibrium sensory using virtual bicycle system. We have used a virtual bicycle system that combines virtual reality technology with a bicycle. In this experiment, 10 subjects were tested to investigate the influencing factors on equilibrium sensory. Straight road and curved road driving at several factors including cycling time, number of times of path deviation, and center of pressure(COP) were extracted and evaluated to quantify the extent of control. Also, To improve the effect of balance training, we investigated the usefulness of virtual feedback information by weight shift. The result showed that the system could be effective for equilibrium sensory rehabilitation training device. The analysis method might also have wider applicability to the rehabilitation field.

• Journal of the Korean Society of Safety
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• v.27 no.1
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• pp.117-122
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• 2012

In recent years, there have been a number of concerns and measures surrounding 'Traffic Safety' for children. But, actually, safety measurements of 'School Zone' lack. This research thesis was designed to quantify risk degrees of 'School Zone', in a simple way, with the development of evaluation indicators to evaluate risk degrees of 'School Zone'. This is deems to be used for a guideline necessary for devising improvements or safety measures against 'School Zone' in the future. And, this is expected to be useful for managing and controlling safety each local facility about elementary schools.