• Journal of Korea Water Resources Association
• /
• v.35 no.5
• /
• pp.463-474
• /
• 2002

A two-dimensional water quality management model, Unsteady/Uncertainty Water Quality Model(UUWQM), is developed for a hydrodynamic analysis, an advection-diffusion analysis, and a reliability analysis by using uncertainty technique. The model is applied to the 35 km reach of Sungju to Hyunpoong in the midstream of Nakdong River. 2-D hydrodynamic and water quality analyses are peformed in this reach. Important input variables are decided by sensitivity analysis and verified by Monte Carlo method. Frequency distributions of water quality concentrations are computed from MFOSM method and Monte Carlo method at several locations in this study area. A water quality management system is constructed by calculating the violation probabilities of existing water quality standards.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.8
• /
• pp.691-697
• /
• 2016

Remanufacturing refers to restoring a used product to an acceptable condition for resale in the market of remanufactured items. In this paper, we deal with the acquisition price and remanufacturing decision for remanufacturing systems in the case where the demand for the remanufactured product in a single period is known and the return quantity of the used product is determined by its acquisition price. The quality of the acquired used product is categorized into two classes, high and low, through inspection and different qualities incur different remanufacturing costs. The probability that the acquired used product is categorized as high class can be a constant or random variable. We derive the expected total cost functions, obtain the optimal solutions, and interpret the managerial meaning of the optimal solution for each case. The sensitivity of the optimal solution with respect to the variation of the inspection cost and uncertainty of the quality of the used product is investigated through numerical examples.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.7
• /
• pp.785-790
• /
• 2011

The goal of this study is to estimate the force acting on the knee joint in the human body by using the Hilltype muscle model based on a musculoskeletal model of the human lower extremity in the sagittal plane. For estimating the force applied, the human leg is modeled using multi-body modeling. This leg model comprises biarticular muscles acting on two joints of the upper and lower limbs, and the muscles include some of the major muscles such as the hamstring. In order to analyze the uncertainty of the applied forces acting on the knee joint, statistical distributions of human body, leg part, parameters are required and to obtain the parameter's statistical characteristic of the part sample survey method is employed. Finally, by using the sensitivity information of the parameters, the force acting on the knee joint can be estimated.

• Journal of Korea Water Resources Association
• /
• v.31 no.5
• /
• pp.553-564
• /
• 1998

For the proper design and management of underground storage cavern, groundwater flow around cavern should be analyzed. Since this flow is influenced by spatial nonuniformity of hudraulic conductivity, the two-dimensional finite element flow model incorporating stochastic concepts was developed to analyze influences due to this nonuniformity. Monte Carlo technique was applied to obtain an approximate solution for two-dimensional, steady flow in a stochastically defined nonuniform medisu. For this purpose, the values of hydraulic conductivity were generated for each element with known mean and standard deviations. The uncertainty in model prediction depends on both the nonuniformity in hydraulic conductivity and the natures of the flow system such as water curtain and boundary condition. Therefore the uncertainties in predicted hydraulic head and gradient are the greatest where the mean hydraulic gradients are relatively large and far from the boundaries. Especially, we relate these uncertainties with well known gas tightness condition.

• Korean Journal of Optics and Photonics
• /
• v.13 no.6
• /
• pp.521-529
• /
• 2002

We have recently proposed the new concept of a phase-measuring volumetric interferometer that enables us to accurately measure the xyz-coordinates of the probe without metrology frames. The interferometer is composed of a movable target and a fixed photo-detector array. The target is made of point diffraction sources to emit two spherical wavefronts, whose interference is monitored by an array of photo-detectors. Phase shifting is applied to obtain the precise phase values of the photo-detectors. Then the measured phases are fitted to a geometric model of multilateration so as to determine the xyz-location of the target by minimizing least square errors. The proposed interferometer has been designed and built with a volumetric uncertainty of less than 1.0 $\mu\textrm{m}$ within a cubic working volume of side 120 mm. Here, in this paper, we also present error sources, an evaluated uncertainty, and test results from the prototype system. The self-calibration of two-dimensional precision metrology stages is applied to test the performance of the interferometer.

• Smart Structures and Systems
• /
• v.17 no.2
• /
• pp.209-230
• /
• 2016

The Canton Tower is a high-rise slender structure with a height of 610 m. A structural health monitoring system has been instrumented on the structure, by which data is continuously monitored. This paper presents an investigation on the identified modal properties of the Canton Tower using ambient vibration data collected during a whole day (24 hours). A recently developed Fast Bayesian FFT method is utilized for operational modal analysis on the basis of the measured acceleration data. The approach views modal identification as an inference problem where probability is used as a measure for the relative plausibility of outcomes given a model of the structure and measured data. Focusing on the first several modes, the modal properties of this supertall slender structure are identified on non-overlapping time windows during the whole day under normal wind speed. With the identified modal parameters and the associated posterior uncertainty, the distribution of the modal parameters in the future is predicted and assessed. By defining the modal root-mean-square value in terms of the power spectral density of modal force identified, the identified natural frequencies and damping ratios versus the vibration amplitude are investigated with the associated posterior uncertainty considered. Meanwhile, the correlations between modal parameters and temperature, modal parameters and wind speed are studied. For comparison purpose, the frequency domain decomposition (FDD) method is also utilized to identify the modal parameters. The identified results obtained by the Bayesian method, the FDD method and a finite element model are compared and discussed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.258-265
• /
• 2017

At the early stage of the development of high speed propulsion systems, the designers suffer from the lack of both the quantity and the quality of test data. In that situation, the associated uncertainties could not be modeled as probabilistic distribution since probabilistic modelling requires large amount of data. In this paper, instead, the information provided by experts based on their experience and engineering knowledge was used to model uncertainty using the evidence theory. In designing the DCR(Dual Combustion Ramjet) engine, the combustion efficiencies, not well understood and little data existing, are assumed to have been provided by experts. And the uncertainties are quantified by Evidence theory. The quantified uncertainties are incorporated into the optimization. The design variables, area of inlet and area of combustor exit, have been found while satisfying reliability margins of thrust and thermal choking. The results show a reasonable design of the engine under the uncertain circumstances.

• Journal of Korea Water Resources Association
• /
• v.51 no.9
• /
• pp.813-826
• /
• 2018

Recently, weather radar system has been widely used for effectively monitoring near real-time weather conditions. The radar rainfall estimates are generally relies on the Z-R equation that is an indirect approximation of the empirical relationship. In this regards, the bias in the radar rainfall estimates can be affected by spatial-temporal variations in the radar profile. This study evaluates the uncertainty of the Z-R relationship while considering the rainfall types in the process of estimating the parameters of the Z-R equation in the context of stochastic approach. The radar rainfall estimates based on the Bayesian inference technique appears to be effective in terms of reduction in bias for a given season. The derived Z-R equation using Bayesian model enables us to better represent the hydrological process in the rainfall-runoff model and provide a more reliable forecast.

• Information Systems Review
• /
• v.5 no.2
• /
• pp.169-182
• /
• 2003

The growth of electronic commerce make business to business electronic commerce market grow dramatically due to dramatic decrease of transaction cost and increase of productivity. It also influences the way of building transaction relationship between buyers and suppliers. This study tends to prove electronic market theory for Internet based 13213 commerce. We observe and analyze the implementation and usage patterns of procurement system of I company. The result shows that even through Internet enable many buyers and suppliers to participate and transact each other, the transaction pattern is different according to asset specificity and uncertainty as follows. First, with adoption of internet, the product with the higher asset specificity rather than lower asset specificity can be easily purchased. Second, Internet doesn't make any significant influence on the transaction of the product with higher uncertainty. But, organization's pre-audit process can indirectly influence on the decrease of the transaction uncertainty.

• The Korean Journal of Franchise Management
• /
• v.12 no.1
• /
• pp.35-44
• /
• 2021

Purpose: This study examines the opportunism moderating effect by the startup experience in the relationship between franchisor and franchisees. In the case of a franchise system that has a continuous relational exchange transaction, relationship management is a very important activity because the relationship management between franchisor and franchisees improves the quality of the relationship. Nevertheless, there is insufficient of research on opportunism, which is a negative factor in managing the relationship between franchisor and franchisees in continuous relationship. Research design, data and methodology: This study, we explore the cause of opportunism based on transaction cost theory through prior research and establish a research model based by goal incongruity, uncertainty, information asymmetry, transaction specific assets, the relevance to determinant of opportunism and the startup experienced which is a moderating variable. To verify several hypotheses, the data were collected from 300 out of 1,760 domestic franchisees and analyzed using multiple regression analysis with SPSS program. Results: The findings are as follows. Goal incongruity did not affect opportunism. Opportunism increased as uncertainty increased, and as information asymmetry increased, opportunism increased. An opportunism decreased as transaction specific assets increased. Moreover, the findings show that startup experience only plays a moderating role in the relationship between information asymmetry and opportunism. Therefore, 4 out of 8 hypotheses were supported. Conclusions: The findings show that uncertainty, information asymmetry, and transaction specific assets are the determinants of opportunism. In addition, the results of the analysis of the moderating role of startup experience show that the less entrepreneurial experience, the greater the influence of information asymmetry on opportunism. Our findings mean that maintaining a successful relationship between franchisors and franchisees is possible when franchisors provide knowledge sharing, goal sharing, environmental sharing, and management information sharing to franchisees. In addition, the findings of this study shows that the contract content and management should be changed according to the entrepreneurial experience. In other words, the franchisors must share and integrate the accumulated franchisees' and franchisors' experience with the franchisees to create a synergy that can lead to successful bilateral relationship maintenance, which in turn reduces opportunism.