• Journal of the Korean Society of Safety
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• v.37 no.1
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• pp.12-19
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• 2022

Circuit breakers are a crucial factor in ensuring the safety of a Direct Current (DC) grid. One type of DC circuit breaker, the Z-source DC circuit breaker (ZCB), uses a thyristor, which is a type of semiconductor switch. In the event of a fault in the circuit, the ZCB isolates the fault by generating a zero crossing current in the thyristor. The thyristor quickly and actively isolates the fault while generating a zero crossing current, but thyristor switch cannot control turn-off and the allowable current is lower than the current of the mechanical switch. Therefore, it is best to use a mechanical switch with a high allowable current capacity that is capable of on/off control. Due to the slow reaction time of mechanical switches, they may not isolate the fault during the zero crossing current time interval created by the existing circuit. In this case, the zero crossing current time can be increased by using the property that hinders the rapid change in the current of the inductor. This paper will explore whether adding system inductance to increase the zero crossing current time interval is a solution to this problem. The simulation of changing inductor and capacitor (LC) of the circuit is repeated to find an optimal change in the zero crossing current time according to the LC change and provides an inductor and capacitor range optimized for a specific load. The inductor and capacitor range are expected to provide optimization information in the form LC values for future applications of ZCB's using a mechanical switch.

• International Journal of High-Rise Buildings
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• v.12 no.1
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• pp.93-105
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• 2023

Seismic isolation and vibration control techniques have been developed and put into practical use by challenging researchers and engineers worldwide since the latter half of the 20th century, and after more than 40 years, they are now used in thousands of buildings, private residences, highways in many seismic areas in the world. Seismic isolation and vibration control structures can keep the structures undamaged even in a major earthquake and realize continuous occupancy. This performance has come to be recognized not only by engineers but also by ordinary people, becoming indispensable for the formation of a resilient society. However, the dynamic characteristics of seismically isolated bearings, the key elements, are highly dependent on the size effect and rate-of-loading, especially under extreme loading conditions. Therefore, confirming the actual properties and performance of these bearings with full-scale specimens under prescribed dynamic loading protocols is essential. The number of testing facilities with such capacity is still limited and even though the existing labs in the US, China, Taiwan, Italy, etc. are conducting these tests, their dynamic loading test setups are subjected to friction generated by the large vertical loads and inertial force of the heavy table which affect the accuracy of measured forces. To solve this problem, the authors have proposed a direct reaction force measuring system that can eliminate the effects of friction and inertia forces, and a seismic isolation testing facility with the proposed system (E-isolation) will be completed on March 2023 in Japan. This test facility is designed to conduct not only dynamic loading tests of seismic isolation bearings and dampers but also to perform hybrid simulations of seismically isolated structures. In this paper, design details and the realization of this system into an actual dynamic testing facility are presented and the outcomes are discussed.

• Journal of Korean Biological Nursing Science
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• v.25 no.3
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• pp.143-159
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• 2023

Purpose: The purpose of this study was to provide evidence for future research by analyzing the contents, delivery methods, and educational effects of educational programs for hemodialysis patients. Methods: A literature review was conducted in the following order: problem identification, literature search and data collection, data evaluation, data analysis, and data presentation. In total, 936 documents were retrieved from the search, and 24 documents were finally included in this study. Results: The contents of the educational programs were comprehensive hemodialysis-related knowledge education in seven studies, exercise-related education in 10 studies, diet-related education in four studies, drug-related education in one study, and complex education in two studies. The delivery methods were pamphlets in six studies, audio-visual materials in four studies, direct guidance by researchers in six studies, and multiple methods in seven studies. The effects of the educational program were divided into physical indicators, emotional indicators, and knowledge and performance related to hemodialysis. Sixteen out of 20 articles using physical indicators showed significant outcomes, and 10 out of 12 articles using emotional indicators derived positive results. Hemodialysis-related knowledge and performance were measured in eight and 10 studies, respectively, and meaningful results were found in six studies for knowledge and seven studies for performance. Conclusion: Future research will require the development of a systematic and standardized educational program with comprehensive content that can be provided to all hemodialysis patients, as well as a highly accessible education delivery method to enhance the effectiveness of education.

• International conference on construction engineering and project management
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• 2007.03a
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• pp.642-652
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• 2007

Many contracting firms and project managers in the construction industry have started to utilize multi objective optimization methods to handle multiple conflicting goals for completing the project within the stipulated time and budget with required quality and safety. These optimization methods have increased the pressure on decision makers to search for an optimal resources utilization plan that optimizes simultaneously the total project cost, completion time, and crashing cost by considering indirect cost, contractual penalty cost etc., practically charging them in terms of direct cost of the project which is fuzzy in nature. This paper presents a multiple fuzzy goal programming model (MFGP) that supports decision makers in performing the challenging task. The model incorporates the fuzziness which stems from the imprecise aspiration levels attained by the decision maker to these objectives that are quantified through fuzzy linear membership function. The membership values of these objectives are then maximized which forms the fuzzy decision. The problem is solved using LINGO 8 optimization solver and the best compromise solution is identified. Comparison between solutions of MFGP, fuzzy multi objective linear programming (FMOLP) and multiple goal programming (MGP) are also presented. Additionally, an interactive decision making process is developed to enable the decision maker to interact with the system in modifying the fuzzy data and model parameters until a satisfactory solution is obtained. A case study is considered to demonstrate the feasibility of the proposed model for optimization of project network parameters in the construction industry.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.962-969
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• 2009

The market of building construction has been competitive in Hong Kong, perhaps as anywhere else in the world. The barrier to entry is low because there are relatively low requirements on the three factors of production - technology, manpower and finance. The prevailing building technology is traditional and labour-intensive. There is also not much need of capital because clients' periodic payments have been the main source of project finance. Further, capitalizing on trade sub-contracting, contractors have been able to keep their direct labour-force small and to transfer much of their business risk to the sub-contractors. Based on interviews to solicit the perception of a sample of building contractors on the particular issues of construction finance, we present the findings in this paper and discuss the various implications. We believe that the current practice of construction financing is both the cause and effect of the competition within, and the competitiveness of, the building construction sector in Hong Kong. We conclude that the building construction sector is "locked or stuck" in this "equilibrium" of traditional technology, reliance on clients' finance and exploitation of sub-contracting. In this "equilibrium" state, there is hardly any motivation for contractors to engage themselves in product or process innovation. Consequently, any talk of industry reform or innovation could only remain just that. We believe that this problem is not unique in Hong Kong. The building construction sector in many other developed and developing economies is posed with similar if not the same problems and constraints. We conclude that there has to be some "external forces" to bring this "equilibrium" state to a higher level "equilibrium" one where higher value-added building construction services are supplied and demanded. This is a state where building contractors possessing innovative technology, better financial and manpower resources could thrive to build better buildings with innovative building methods and processes.

• Journal of Korea Society of Industrial Information Systems
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• v.14 no.1
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• pp.43-55
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• 2009

We consider a Direct Input Output Manufacturing System(DIOMS) which has a number of machine centers placed along a built-in Automated Storage/Retrieval System(AS/RS). The Storage/Retrieval (S/R) machine handles parts placed on pallets for the operational aspect of DIOMS and determines the optimal operating policy by combining computer simulation and genetic algorithm. The operational problem includes: input sequencing control, dispatching rule of the SIR machine, machine center-based part type selection rule, and storage assignment policy. For each operating policy, several different policies are considered based on the known research results. In this paper, using the computer simulation and genetic algorithm we suggest a method which gives the optimal configuration of operating policies within reasonable computation time.

• Research in Plant Disease
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• v.28 no.4
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• pp.195-203
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• 2022

Zea mays, known as maize or corn, is a major staple crop and an important source of energy for humans and animals, thus ensuring global food security. Approximately 9.4% of the loss of total annual corn production is caused by pathogens including fungi, bacteria, and viruses, resulting in economic losses. Although the use of fungicides is one of the most common strategies to control corn diseases, the frequent use of fungicides causes various health problems in humans and animals. In order to overcome this problem, an eco-friendly control strategy has recently emerged as an alternative way. One such eco-friendly control strategy is the use of beneficial microorganisms in the control of plant pathogens. The beneficial microorganisms can control the plant pathogens in various ways, such as spatial competition with plant pathogens, inhibition of fungal or bacterial growth via the production of secondary metabolites or antibiotics, and direct attack to plant pathogens via enzyme activity. Here, we reviewed microorganisms as biocontrol agents against corn diseases.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.59 no.1
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• pp.55-64
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• 2023

Gas turbine engines are widely used as prime movers of generator and propulsion system in warships. This study addresses the problem of designing a DS-based PID controller for speed control of the LM-2500 gas turbine engine used for propulsion in warships. To this end, we first derive a dynamic model of the LM-2500 using actual sea trail data. Next, the PRC (process reaction curve) method is used to approximate the first-order plus time delay (FOPTD) model, and the DS-based PID controller design technique is proposed according to approximation of the time delay term. The proposed controller conducts set-point tracking simulation using MATLAB (2016b), and evaluates and compares the performance index with the existing control methods. As a result of simulation at each operating point, the proposed controller showed the smallest in %OS, which means that the rpm does not change rapidly. In addition, IAE and IAC were also the smallest, showing the best result in error performance and controller effort.

• 한국정보교육학회:학술대회논문집
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• 2021.08a
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• pp.303-308
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• 2021

In this study, we intended to present a class design plan that combines safety education and software education, which are very important in the school field, but are considered necessary for change. In order to realize safety education centered on indirect experience, the 12th class plan was devised as a "Smart Safety Commuter Road Production Project" using a physical computing tool called Bitbrick. Based on the 12th city's class plan, qualitative research was conducted with interviews with a total of five teachers, showing both the effectiveness and problems of applying them to the class. The effectiveness is that unlike conventional delivery-type safety education, indirect experience-oriented safety education centered on real-life situations is possible, and it can be expected that procedural thinking skills can be developed along with stimulating interest. However, the problem has been shown that the process of implementing the direct situation can be challenging and that even activities can be more efficient than group activities.

• Journal of Environmental Science International
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• v.32 no.6
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• pp.453-464
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• 2023

To this day, conflicts have intensified between managers who want to preserve biosphere reserves and citizen who want to develop them. Based on this problem, this study seeks to investigate the establishment of a forum for communication between various stakeholders and to promote the economic development of local communities while preserving biodiversity. First, in terms of conservation, the results indicated that Gyeonggi Province and Namyangju City highly valued direct conservation activities in biosphere reserves, whereas Pocheon and Uijeongbu City highly valued indirect conservation functions through management or monitoring. Second, in terms of development, it was found that there were differences in the roles, perceptions and responsibilities with respect to biosphere reserves among the different layers of government: the central government agency, the Cultural Heritage Administration, the metropolitan government, Gyeonggi-do, and the local governments, Pocheon, Namyangju, and Uijeongbu. Third, in terms of logistical support, which serves as a function for communication and practical participation among management entities, the results suggested that it was necessary to establish a comprehensive decision-making organization for efficient management and operation and to provide opportunities for active participation. The study can be utilized as a basic reference for developing efficient communication by management entities in protected areas with similar challenges.