• Nuclear Engineering and Technology
• /
• v.56 no.4
• /
• pp.1472-1479
• /
• 2024

Cyber-Physical Energy Systems (CPESs) integrate cyber and hardware components to ensure a reliable and safe physical power production and supply. Renewable Energy Sources (RESs) add uncertainty to energy demand that can be dealt with flexible operation (e.g., load-following) of CPES; at the same time, scenarios that could result in severe consequences due to both component stochastic failures and aging of the cyber system of CPES (commonly overlooked) must be accounted for Operation & Maintenance (O&M) planning. In this paper, we make use of Deep Reinforcement Learning (DRL) to search for the optimal O&M strategy that, not only considers the actual system hardware components health conditions and their Remaining Useful Life (RUL), but also the possible accident scenarios caused by the failures and the aging of the hardware and the cyber components, respectively. The novelty of the work lies in embedding the cyber aging model into the CPES model of production planning and failure process; this model is used to help the RL agent, trained with Proximal Policy Optimization (PPO) and Imitation Learning (IL), finding the proper rejuvenation timing for the cyber system accounting for the uncertainty of the cyber system aging process. An application is provided, with regards to the Advanced Lead-cooled Fast Reactor European Demonstrator (ALFRED).

• Journal of the Korean Society of Hazard Mitigation
• /
• v.10 no.1
• /
• pp.89-102
• /
• 2010

Future uncertainty on water demand caused by future climate condition and water consumption leads a difficulty to determine the reservoir operation rule for supplying sufficient water to users. It is, thus, important to operate reservoirs not only for distributing enough water to users using the limited water resources but also for preventing floods and drought under the unknown future condition. In this study, the reservoir storage is determined in the first stage when future condition is unknown, and then, water distribution to users and river stream is optimized using the available water resources from the first stage decision using 2-stage stochastic linear programming (2-SLP). The objective function is to minimize the difference between target and actual water storage in reservoirs and the water shortage in users and river stream. Hedging rule defined by a precaution against severe drought by restricting outflow when reservoir storage decreases below a target, is also applied in the reservoir operation rule for improving the model applicability to the real system. The developed model is applied in a system with five reservoirs in the Han River basin, Korea to optimize the multi-reservoir system under various future water demand scenarios. Three multi-purposed dams - Chungju, Hoengseong, and Soyanggang - are considered in the model. Gwangdong and Hwacheon dams are also considered in the system due to the large capacity of the reservoirs, but they are primarily for water supply and power generation, respectively. As a result, the water demand of users and river stream are satisfied in most cases. The reservoirs are operated successfully to store enough water during the wet season for preparing the coming drought and also for reducing downstream flood risk. The developed model can provide an effective guideline of multi-reservoir operation rules in the basin.

• Journal of Korea Water Resources Association
• /
• v.55 no.7
• /
• pp.505-513
• /
• 2022

Recently, uncertainty in predicting available water resources is gradually increasing due to climate change and extreme weather conditions. Social interest in water management such as flood and drought prevention is also increasing, and after the unification of water management implemented in 2018, domestic water management is facing a major turning point. As part of such strengthening of water management capabilities, various studies are being conducted to utilize a hydropower dam for flood control and water supply purposes, which was mainly operated for hydroelectric power generation. However, since the dam evaluation methods developed based on a multi-purpose dam are being applied to hydropower dams, an additional evaluation approach that can consider the characteristics of hydropower dams is required. In this study, a new water supply capacity evaluation method is presented in consideration of the operational characteristics of hydropower dams in terms of water supply, and a connected reservoir simulation method is proposed to evaluate the comprehensive water supply capacity of a dam group operating in a river basin. The presented method was applied to the hydropower dams located in the Bukhan River basin, and the results of the water supply yield of individual dams and multi-reservoir systems were compared and analyzed. In the future, the role of hydropower dams for water supply during drought is expected to become more important, and this study can be used for sustainable domestic water management research using hydropower dams.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
• /
• v.12 no.5
• /
• pp.117-126
• /
• 2017

This study analyzed both the effect small and medium-sized suppliers' SCM capacity on the performance and how the moderating effect of demand uncertainty as an environmental factor affects this relation. The study is based on the data collected from the survey of small and medium-sized suppliers operating in electronics, metal, machinery, automobile, and textile. It analyzed the results of survey targeting suppliers of these areas by using structure equation modeling. According to the analyzed result, the relation capital of small and medium-sized supplier affects the performance, but there is no relation between coordination capability and the performance. In case of the moderating effect of demand uncertainty, while there is a positive moderating effect of demand uncertainty between relation capital and performance, there is no any moderating effect between coordination capability and performance. It turns out that the relation capital keep having a positive effect on the performance even if there is a demand uncertainty.

• Journal of Korea Water Resources Association
• /
• v.43 no.2
• /
• pp.131-138
• /
• 2010

Due to the increased water demand and severe drought as an effect of the global warming, the effluent from wastewater treatment plants becomes considered as an alternative water source to supply agricultural, industrial, and public (gardening) water demand. The effluent from the wastewater treatment plant is a sustainable water source because of its good quality and stable amount of water discharge. In this study, the water reuse system was developed to minimize total construction cost to cope with the uncertain water demand in future using two-stage stochastic linear programming with binary variables. The pipes in the water reuse network were constructed in two stages of which in the first stage, the water demands of users are assumed to be known, while the water demands in the second stage have uncertainty in the predicted value. However, the water reuse system has to be designed now when the future water demands are not known precisely. Therefore, the construction of a pipe parallel with the existing one was allowed to meet the increased water demands in the second stage. As a result, the trade-off of construction costs between a pipe with large diameter and two pipes having small diameters was evaluated and the optimal solution was found. Three scenarios for the future water demand were selected and a hypothetical water reuse network considering the uncertainties was optimized. The results provide the information about the economies of scale in the water reuse network and the long range water supply plan.

• Knowledge Management Research
• /
• v.11 no.5
• /
• pp.59-78
• /
• 2010

In this paper, we arrange the concept of 'Green' in SCM after literature study of Green SCM and investigate causal relationships between influencing factors, practice level and environmental performance focused on Korean firms empirically and conduct path analysis for hypothesis test using partial least squares regression with bootstrap. Firstly, we divide influencing factors of Green SCM into environmental and organizational factors through the previous studies of innovation diffusion theory and environmental management theory, and then we selected 'uncertainty', 'competitiveness' as the environmental factors and 'top management support', 'perceived benefit', 'training' as the organizational factors. Secondly, we classify practice level of Green SCM into 'internal environmental management', 'green purchasing', 'eco-design'. Finally, we selected 'financial performance', 'environmental performance' as the organizational performance. We conducted a survey on the middle manager of manufacturing companies implementing SCM and an empirical analysis. The results of analysis show that there exist causal relationships between influencing factors, practice level, and environmental performance of Green SCM. We expect that the result of this study will suggest useful information to managers who are responsible for SCM to design and execute Green SCM in strategic perspectives.

• Proceedings of the KIEE Conference
• /
• 2000.07a
• /
• pp.406-408
• /
• 2000

Recently, Korea's electric industry is in the midst of a period of profound changes in the structure and function, including the introduction of market competition in the generation sector. Therefore, it is difficult to promote long-term capacity planning and new generating capacity construction which have been driven by KEPCO so far, after the introduction of market competition, so new generating capacity construction and security of reserve margin is needed through self·regulation plan of private generation producers by market mechanism. According to the competition in the generation sector, a new paradigm is necessary to the long-term capacity planning driven by the Government. This paper analyzes the plan and the incentive level able to guide the new generation capacity construction considering the uncertainty risk in a period of introduction of competition. In addition, this paper analyzes the plan able to guide the new capacity construction by market function at the stage which market become established and Government's role to solve the anxiety about the capacity supply and demand.

• Journal of the Korea Safety Management & Science
• /
• v.17 no.1
• /
• pp.149-168
• /
• 2015

It is expected that the temperature in Pyeongyang will be similar to that ($16.6^{\circ}C$) in Seogwipo in the late 21st century, and most of South Korea will enter the subtropical climate due to climate change. Change in the precipitation pattern like the range of fluctuation caused by climate change will lead to expanded uncertainty in securing reliable water supply, along with a serious impact on demands for living and industrial water due to change in the volume and period of river outflow. As industrial water for production activities is estimated based on the contract quantity, it is difficult to apply rationalization of water usage and incentives in water recycling. Therefore many companies are making efforts in complying with the effluent standard while spending few resources on such rationalization and recycling. This study researched water risk management over 115 Korean companies by 28 questions in 4 categories. Through the research, this study aims to understand water risk management levels and seek response plans.

• Journal of Korean Society of Water and Wastewater
• /
• v.25 no.3
• /
• pp.293-305
• /
• 2011

A special concern is paid to the risks with which small-sized water resources systems are confronted in supplying water in the far future. Taking the Gwangdong dam reservoir as a case study, the authors seek to understand demand-side and supply-side disturbances of a reservoir, which, respectively, corresponds to effects of water demand changes on the intake amount and those of climate changes on the inflow amount. In result, it is demonstrated that both disturbances in the next 50 years are almost unpredictable. Yet the projection ranges, thought of as relatively reliable information that models offer, reveal that severity and period of water shortage is very likely to change. It is therefore concluded that water resources management requires more rigorous approaches to overcoming high uncertainties. The methods and models for projecting those disturbances are selected, based on practicality and applicability. Nevertheless, they show a large usefulness, especially in dealing with data shortage and reducing the needs for expensive modeling resources.

• Korean Management Science Review
• /
• v.33 no.1
• /
• pp.17-33
• /
• 2016

This study investigated the relationships among proper types of e-commerce, patterns of inter-organizational information flow (IIF), benefits of e-commerce, and supply-chain performance. In IIF, it was empirically observed that environmental competition positively influences the frequency of IIF, and environmental uncertainty has a positive impact on the quality of IIF. It was also empirically confirmed that only quality of IIF has effects on the usage levels of e-procurement as well as e-partnerships. Through regression analyses and cluster analysis, it was found that under high degrees of the frequency and quality of IIF, the benefits of e-commerce are vastly realized in the firms that highly utilize e-partnerships. The results of this study also showed that when the degrees of quality of IIF are high, the levels of benefits of e-commerce are increased in the firms that employ e-procurement. The moderating effects of buyer and supplier firms' abilities on the relationships between patterns of IIF and usage levels in various types of e-commerce were empirically examined. According to the results, the moderating roles of buyer firms' capabilities and suppliers' abilities were partially demonstrated. Finally, it was found that the realization of benefits of e-commerce can lead to the improvement of supply-chain performance.