• Journal of the Korean Society of Systems Engineering
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• v.11 no.1
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• pp.9-24
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• 2015

Construction industry faces a lot of inherent uncertainties and issues and the construction phase of nuclear power project is not free from this risk. This paper investigates promising methodologies to be used on nuclear power plant (NPP) construction schedule delay risk assessment by using entry level systems engineering approach. This study contains how the initial concept for the risk assessment methodology has been developed. In this point of view, this work structured on three main phases: needs analysis (NA), concept exploration (CE), and concept definition (CD) through systems engineering (SE) approach. Traditionally, the SE process is applied to technical development programs but this study opens up a new avenue that SE can also be successfully applied to the development and optimization of the risk assessment model. This study provides a rational and systematic process for developing and selecting the best risk assessment model. This paper selects analytic hierarchy process (AHP) method to assess NPP construction schedule delay risk for international project. As conclusion, the proposed concept and selected method can discriminate successfully and clearly among schedule delay risk assessment methods.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.12
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• pp.3117-3132
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• 2012

The tree topology in multicast systems has high transmission efficiency, low latency, but poor resilience to node failures. In our work, some nodes are selected as backbone nodes to construct a tree-like core overlay. Backbone nodes are reliable enough and have strong upload capacity as well, which is helpful to overcome the shortcomings of tree topology. The core overlay is organized into a spanning tree while the whole overlay is of mesh-like topology. This paper focuses on improving the performance of the application-layer multicast overlay by optimizing the core overlay which is periodically adjusted with the proposed optimization algorithm. Our approach is to construct the overlay tree based on the out-degree weighted reliability where the reliability of a node is weighted by its upload bandwidth (out-degree). There is no illegal solution during the evolution which ensures the evolution efficiency. Simulation results show that the proposed approach greatly enhances the reliability of the tree-like core overlay systems and achieves shorter delay simultaneously. Its reliability performance is better than the reliability-first algorithm and its delay is very close to that of the degree-first algorithm. The complexity of the proposed algorithm is acceptable for application. Therefore the proposed approach is efficient for the topology optimization of a real multicast overlay.

• Korean Journal of Agricultural Science
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• v.45 no.4
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• pp.859-870
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• 2018

Dried red peppers are a staple agricultural product used in Korean cuisine and as such, are an important aspect of agricultural producers' income. Correctly forecasting both their supply and demand situations and price is very important in terms of the producers' income and consumer price stability. The primary objective of this study was to compare the performance of time series forecasting models for dried red peppers in Korea. In this study, three models (an autoregressive model with exogenous variables [ARX], AR-exponential generalized autoregressive conditional heteroscedasticity [EGARCH], and ARX-EGARCH) are presented for forecasting the wholesale price of dried red peppers. As a result of the analysis, it was shown that the ARX model and ARX-EGARCH model, each of which adopt both the rolling window and the adding approach and use the agricultural cooperatives price as the exogenous variable, showed a better forecasting performance compared to the autoregressive model (AR)-EGARCH model. Based on the estimation methods and results, there was no significant difference in the accuracy of the estimation between the rolling window and adding approach. In the case of dried red peppers, there is limitation in building the price forecasting models with a market-structured approach. In this regard, estimating a forecasting model using only price data and identifying the forecast performance can be expected to complement the current pricing forecast model which relies on market shipments.

• Journal of Preventive Medicine and Public Health
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• v.57 no.2
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• pp.157-166
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• 2024

Objectives: Children with disabilities may exhibit a multitude of symptoms, and treatment requires a multidisciplinary approach for a satisfactory outcome. Lack of awareness among physicians, lack of referral, and lack of inter-sectoral coordination have hindered paediatric practice in Tamil Nadu, a state in India with a striking childhood disability rate that warrants a timely interdisciplinary approach. However, the perspectives of paediatricians on paediatric physiotherapy are unknown. The aim of the study was to investigate the perspectives of practicing paediatric physicians in Chennai on the role of physiotherapy in paediatrics. Methods: For an in-depth exploration, qualitative semi-structured interviews were conducted in person with 10 paediatricians. Audio from the sessions was recorded and transcribed, and data saturation was achieved through iterative analysis. Results: A grounded theory analysis of the results yielded 5 domains under which the perspectives and expectations of the physicians were described, along with the barriers experienced by patients' parents as explained by their paediatrician. The responses highlighted deficits in awareness, structural support, accessibility and direct communication between physicians and physiotherapists. Conclusions: Paediatric physicians have different opinions, and some ignorance persists concerning paediatric physiotherapy. This study warrants a proper structure of the paediatric rehabilitation unit and regular interdisciplinary meetings and focus group discussions to increase access for parents and improve patient outcomes.

• Nuclear Engineering and Technology
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• v.55 no.12
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• pp.4395-4407
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• 2023

Bubble columns are widely encountered in several industries, especially in the field of nuclear safety. The Eulerian-Eulerian and the Eulerian-Lagrangian methods are commonly used to investigate bubble columns. Eulerian approaches require additional tasks such as strict volume conservation at the interface and a predefined well-structured grid. In contrast, the Lagrangian approach can be easily implemented. Hence, we introduce a fully Lagrangian approach for the simulation of bubble columns using the discrete bubble model (DBM) and moving particle semi-implicit (MPS) methods. Additionally, we propose a rigorous method to estimate the volume fraction accurately, and verified it through experimental data and analytical results. The MPS method was compared with the experimental data of Dambreak. The DBM was verified by analyzing the terminal velocity of a single bubble for each bubble size. It agreed with the analytical results for each of the four drag correlations. Additionally, the improved method for calculating the volume fraction showed agreement with the Ergun equation for the pressure drop in a packed bed. The implemented MPS-DBM was used to simulate the bubble column, and the results were compared with the experimental results. We demonstrated that the MPS-DBM was in quantitative agreement with the experimental data.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10b
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• pp.100-104
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• 1993

In Part 1, we derived robust stability conditions for an LTI interconnected to time-varying nonlinear perturbations belonging to several classes of nonlinearities. These conditions were presented in terms of positive definite solutions to LMI. In this paper we address a problem of synthesizing feedback controllers for linear time-invariant systems under structured time-varying uncertainties, combined with a worst-case H$_{2}$ performance. This problem is introduced in [7, 8, 15, 35] in case of time-invariant uncertainties, where the necessary conditions involve highly coupled linear and nonlinear matrix equations. Such coupled equations are in general difficult to solve. A convex optimization approach will be employed in this synthesis problem in order to avoid solving highly coupled nonlinear matrix equations that commonly arises in multiobjective synthesis problem. Using LMI formulation, this convex optimization problem can in turn be cast as generalized eigenvalue minimization problem, where an attractive algorithm based on the method of centers has been recently introduced to find its solution [30, 361. In the present paper we will restrict our discussion to state feedback case with Popov multipliers. A more general case of output feedback and other types of multipliers will be addressed in a future paper.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 1999.12a
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• pp.557-575
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• 1999

As the Internet has been used widely in modern firms for gaining competitive advantage in the market, EC (Electronic Commerce) emerged as one of strong alternatives for this purpose. Many researchers and practitioners have proposed a wide variety of EC frameworks that can consider only the structured conditions, but there exists no EC mechanism in which engaged entities can take into account the various unstructured conditions. With the conventional EC framework, the structured EC conditions such as price, quantity, delivery date, etc. can be fully negotiated during the EC process. However, no studies have been conducted on the issue of incorporating those unstructured conditions which are difficult to represent in an explicit form and therefore hard to consider explicitly during the EC process. They are characterized by causal properties. This means that we should have a new EC mechanism which is capable of dealing with causal knowledge. In this sense, we propose a FCM (Fuzzy Cognitive Map)-based simulation framework for EC to resolve the problem of considering the unstructured conditions during the EC process. We experimented our prototype with several illustrative examples and proved that our approach is robust and meaningful.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 1999.12a
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• pp.537-555
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• 1999

As the Internet has been used widely in modern firms for gaining competitive advantage in the market, EC (Electronic Commerce) emerged as one of strong alternatives for this purpose. Many researchers and practitioners have proposed a wide variety of EC frameworks that can consider only the structured conditions, but there exists no EC mechanism in which engaged entities can take into account the various unstructured conditions. With the conventional EC framework, the structured EC conditions such as price, quantity, delivery date, etc. can be fully negotiated during the EC process. However, no studies have been conducted on the issue of incorporating those unstructured conditions which are difficult to represent in an explicit form and therefore hard to consider explicitly during the EC Process. They are characterized by causal properties. This means that we should have a new EC mechanism which is capable of dealing with causal knowledge. In this sense, we propose a FCM (Fuzzy Cognitive Map)-based simulation framework for EC to resolve the problem of considering the unstructured conditions during the EC process. We experimented our prototype with several illustrative examples and proved that our approach is robust and meaningful.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.4
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• pp.19-25
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• 2008

This paper proposes a hierarchically structured navigation algorithm for autonomous mobile robot under unknown environment based on fuzzy-neal network. The proposed algorithm consists of two basic layers as follows. The lower layer consists of two parts such as fuzzy algorithm for goal approach and fuzzy-neural algorithm for obstacle avoidance. The upper layer which is basically fuzzy algorithm adjusts the magnitude of the weighting factor depending on the environmental situation. The proposed algorithm provides an efficient method to escape local mimimum points as shown in the simulation result. Most simulation results show that this algorithm is very effective for autonomous mobile robots' traveling in unknown field.

• The Journal of Sustainable Design and Educational Environment Research
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• v.8 no.2
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• pp.1-11
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• 2009

The school complex project is driven by public calling for school facilities change due to the social change followed by the aging society and increasing interest in the lifelong education. The school complex project is defined as an activity in which the school facilities and space are not only used for students, but also for the local residents. Since the project was promoted in a link with reform of the education system in 2001, the demand in the expectation effect has been sharply increasing. Despite of the high expectation and attention, the school complex project, however, has been performed in a limit of efficiency. Consequently, public opinion calling for more structured and effective way on construction and administration has been certainly increasing. According to the strong demand, this study was carried out to provide basic data for, and suggest an approach to, more structured and effective way of establishment and administration of the school complex project by comparing the success cases in Seoul metropolitan city.