• Nuclear Engineering and Technology
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• v.52 no.12
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• pp.2717-2724
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• 2020

Silicon, especially silicon in the form of SiO₂, is a major component of rocks. Final spent fuel storages, which are being designed, are located in suitable rock formations in the Earth's crust. Reduction of the uncertainty of silicon neutron scattering and capture is needed; improved silicon evaluations have been recently produced by the ORNL/IAEA collaboration within the INDEN project. This paper deals with the nuclear data validation of that evaluation performed at the LR-0 reactor by means of critical experiments and measurement of reaction rates. Large amounts of silicon were used both as pure crystalline silicon and SiO₂ sand. The critical moderator level was measured for various core configurations. Reaction rates were determined in the largest core configuration. Simulations of the experimental setup were performed using the MCNP6.2 code. The obtained results show the improvement in silicon cross-sections in the INDEN evaluations compared to existing evaluations in major libraries. The new Thermal Scattering Law for SiO₂ published in ENDF/B-VIII.0 additionally reduces the discrepancy between calculation and experiments. However, an unphysical peak is visible in the neutron spectrum in SiO₂ obtained by calculation with the new Thermal Scattering Law.

• Progress in Medical Physics
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• v.32 no.4
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• pp.122-129
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• 2021

Purpose: This study aimed to design a multipurpose dose verification phantom for external audits to secure safe and optimal radiation therapy. Methods: In this study, we used International Atomic Energy Agency (IAEA) LiF powder thermoluminescence dosimeter (TLD), which is generally used in the therapeutic radiation dose assurance project. The newly designed multipurpose phantom (MPP) consists of a container filled with water, a TLD holder, and two water-pressing covers. The size of the phantom was designed to be sufficient (30×30×30 cm³). The water container was filled with water and pressed with the cover for normal incidence to be fixed. The surface of the MPP was devised to maintain the same distance from the source at all times, even in the case of oblique incidence regardless of the water level. The MPP was irradiated with 6, 10, and 15 MV photon beams from Varian Linear Accelerator and measured by a 1.25 cm³ ionization chamber to get the correction factors. Monte Carlo (MC) simulation was also used to compare the measurements. Results: The result obtained by MC had a relatively high uncertainty of 1% at the dosimetry point, but it showed a correction factor value of 1.3% at the 5 cm point. The energy dependence was large at 6 MV and small at 15 MV. Various dosimetric parameters for external audits can be performed within an hour. Conclusions: The results allow an objective comparison of the quality assurance (QA) of individual hospitals. Therefore, this can be employed for external audits or QA systems in radiation therapy institutions.

• Journal of the Korea Safety Management & Science
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• v.24 no.2
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• pp.67-76
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• 2022

Power generation construction projects involving large amounts of capital can affect the survival of a company along with huge economic losses in the event of a business failure. In general, private companies are organizations with challenging risk taking tendencies while public companies have a risk averse tendency to avoid risk, so these differences in organizational tendencies make it difficult to respond to risk. In particular, public companies are more likely to fail than private companies because they choose the contradiction of risk picking to enter overseas markets with high uncertainty despite their tendency to risk averse due to the nature of the organization. Therefore, these organizations need risk management techniques that reflect a risk-averse strategy. Accordingly, this paper analyzes the risk management research papers of the existing overseas development EPC business in order to find the risk management techniques related to the organizational tendencies of public companies and proposes "establishing a performance audit system for risk management of the organizational tendencies of public companies" as a way to extract the risk factors through the examples of overseas development projects of public companies and to manage the organizational tendencies of public companies that affect them.

• Geomechanics and Engineering
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• v.28 no.1
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• pp.65-75
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• 2022

Time and cost of construction are key factors in decision-making during a tunnel project's planning and design phase. Estimations of time and cost of tunnel construction projects are subject to significant uncertainties caused by uncertain geotechnical and geological conditions. The Gaussian Process Regression (GPR) technique for predicting ground condition and construction time and cost of mountain tunnel projects is used in this work. The GPR model is trained with data from past mountain tunnel projects. The model is applied to a case study in which the predicted time and cost of tunnel construction using the GPR model are compared with the actual construction time and cost for model validation and reducing the uncertainty for the future projects. In addition, the results obtained from the GPR have been compared with to other models of artificial neural network (ANN) and support vector regression (SVR) that the GPR model provides more accurate results.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.48-49
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• 2020

Recently the diversification of construction market and the continuous reduction of construction amount are raising the need of alternative delivery method in the construction industry. The foreign advanced companies actively adopted the CM at Risk delivery method where they perform the service of agent CM in the design phase, and agree GMP(Guaranteed Maximum Price) with the client at the time of 50~80% completion of design. Even in Korea they began to apply that method to pilot projects. In CM at Risk, through the early participation of builder, the level of design completion can be improved and the change order and construction period delay can be minimized. On the other hand, GMP is usually calculated when the design is about 80% complete, so there is uncertainty in the construction cost. Therefore, in this research, the increased amounts of construction cost are analyzed in a number of public construction projects, and GMP calculation process is proposed using the analysis results and CBR(Case-Based Reasoning) technique to reduce the construction cost increase in the construction phase.

• International conference on construction engineering and project management
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• 2015.10a
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• pp.289-293
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• 2015

The construction industry has been evolving with the development of information technology. According to this trend, the current industry changes from 2d drawings to Building Information Modeling(BIM). Current studies on the BIM-based estimation have problems such as Quantity Take-Off(QTO) specificity toward a particular software, the uncertainty of the amount in accordance with the model quality. These studies focus on QTO based on BIM rather than schematic estimation. In addition, studies on the connection with the QTO and unit cost for schematic estimation are insufficient. The purpose of this study is to propose schematic estimation process by utilizing construction codes and QTO in architectural object BIM libraries. Construction codes are classified in detail in order to input codes inside each. This study has connected unit cost and construction classification codes that obtain from BIM model. The results of this study will be helpful in decision-making and communication for schematic estimation of the design phase. It will improve the efficiency and reliability problems of existing schematic estimation.

• International conference on construction engineering and project management
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• 2011.02a
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• pp.340-349
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• 2011

During the negotiation and resolution of delay and disruption disputes on construction projects, the use and misappropriation of float, and the question of float ownership, are considered to be a major concern to those involved. Most practitioners and authors are of the opinion that it is an issue that should be clearly defined and addressed within the provisions of the contract. However, the terms "float" or "ownership of float" are rarely mentioned (if at all) in most of the standard forms of Australian construction contracts, giving little guidance to those involved as to how this issue should be addressed. In October 2002 the United Kingdoms Society of Construction Law (SCL) published a Delay and Disruption Protocol (the Protocol) that contains a suggested approach to the issue. The aim of this research was to obtain an Australian opinion of the suitability of the SCL's Delay and Disruption Protocols suggested approach to the issue of float and ownership of float for use by the Australian construction industry. Qualitative interviews were carried out with Australian construction industry experts experienced in the administration, negotiation, and resolution of delay and disruption disputes to obtain their opinions of the suitability of the SCL's proposed approach. Results indicate general confusion and uncertainty as to how the issue of float and float ownership should be addressed in general, with the SCL's approach adding further to that confusion.

• Journal of Korean Society of Transportation
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• v.34 no.5
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• pp.421-436
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• 2016

Public-Private-Partnerships tend to be committed high project development cost and recover the cost through future revenue during the operation period. In general, long-term concession can bring on more revenue to private investors, but short-term concession less revenue due to the short recovering opportunities. The concession period is usually determined by government in advance or by the private sectors's proposal although it is a very crucial factor for the PPPs. Accurate traffic forecasting should be most important in planing and evaluating the operation period in that the forecasted traffic determines the project revenue with user fees in PPPs. In this regards, governments and the private investors are required to consider the traffic forecast risk when determining concession period. This study proposed a model for the optimal concession period in the PPPs transportation projects. Monte Carlo simulation was performed to find out the optimal concession period while traffic forecast uncertainty is considered as a project risk under the expected return of the private sector. The simulation results showed that the optimal concession periods are 17 years and 21 years at 5.5% and 7% discount level, respectively. This study result can be applied for the private investors and/or any other concerned decision makers for PPPs projects to set up a more resonable concession period.

• KDI Journal of Economic Policy
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• v.34 no.1
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• pp.135-168
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• 2012

This study analyzes ways to detect protest responses (hereafter, PR zero-bid) in the contingent valuation method (CVM). In order to distinguish PR zero-bids from true zero-bids (non-PR zero bids), this study adopts the concept of the implicit willingness to pay employing the Hicksian compensating surplus and the Taylor's 1st order approximation. When a respondent proposes a zero-bid (i.e., WTP=0) and chooses a PR filtering item to indicate that her implicit WTP is not necessary zero, her response is identified as a PR zero bid. PR filtering items falling into the PR zero bids category include the uncertainty of information, distrust in the government and project achievement, disagreement to project plans, discontent with the fairness of public works and their payment method and animosity against the CVM itself. The empirical analysis shows that PR zero bids take place systematically in particular respondent groups: respondents who have never used similar facilities before nor plans to use the facility provided by the public project, the employed, and low income groups. In conclusion, the study suggests that a CVM questionnaire needs to be designed carefully to minimize problems associated with PR zero bids and the potential risks of having sample selection bias should be concerned.

• Journal of Technology Innovation
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• v.20 no.2
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• pp.29-48
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• 2012

As the complexity and uncertainty of social and economic systems increase, the strategic foresight that actively and effectively responds to the environmental changes becomes important. A wide range of future forecasting methods are available for strategic foresight. Selecting one of the methods depends on several factors such as availability of time and financial resources and the objectives of the exercise. Although trend extrapolation analysis has been used for many years, scenario planning is being widely used by government and corporate as a tool for strategic decision making in recent years. Generally, scenario planning is carried out through workshop, in which experts with diverse backgrounds exchange information, views, and insights and integrate the diverse viewpoints. However, only a small number of experts can participate in a workshop and citizen opinion is not easily transformed into the policy for the scenario exercise due to the limitation of budget and short duration of a project. It is also much harder to develop creative ideas in the workshop because of the limited time and space. In this study, a new scenario process combining scenario workshop and wiki is proposed to overcome the limitation of scenario workshop. This combined approach can be more productive than using scenario workshop alone when developing new ideas. In this study, we applied the combined approach to develop scenarios for the strategic foresight of future media and present suggestions for improving the process.