• Journal of Power Electronics
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• v.14 no.2
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• pp.271-281
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• 2014

Fluctuating wind conditions necessitate the use of a variable speed wind turbine (VSWT) with a AC/DC/AC converter scheme in order to harvest the maximum power from the wind and to decouple the synchronous generator voltage and frequency from the grid voltage and frequency. In this paper, a combination of a three phase diode bridge rectifier (DBR) and a modified topology of the diode clamped multilevel inverter (DCMLI) has been considered as an AC/DC/AC converter. A control strategy has been proposed for the DCMLI to achieve the objective of grid interface of a wind power system together with local load compensation. A novel fixed frequency current control method is proposed for the DCMLI based on the level shifted multi carrier PWM for achieving the required control objectives with equal and uniform switching frequency operation for better control and thermal management with the modified DCMLI. The condition of the controller gain is derived to ensure the operation of the DCMLI at the fixed frequency of the carrier. The converter current injected into the distribution grid is controlled in accordance with the wind power availability. In addition, load compensation is performed as an added facility in order to free the source currents being fed from the grid of harmonic distortion, unbalance and a low power factor even though the load may be unbalanced, non-linear and of a poor power factor. The results are validated using PSCAD/EMTDC simulation studies.

• The KIPS Transactions:PartB
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• v.9B no.6
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• pp.845-852
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• 2002

Electronic document processing using EDl (Electronic Data Interchange) must exchange documents using VAN (Value Added Network). However. the use of exclusive software needs alteration of a new document and the use of VAN(Value Added Network) demands an exchange of document and high cost for maintenance. Due to these problems, the existing EDI (Electronic Data Interchange) is turning into Web-based EDI (Electronic Data Interchange). This paper suggests techniques that change EDI (Electronic Data Interchange) messages which exist in two relational databases into XML (extensible Markeup Language) using the JDBC bridge. Also this paper proposes a method that recovers schema using converted XML (extensible Markeup Language) file, and a method which inserts an original record into a declared table. This solves the limitation of an original method that have to use sane database management system and also overcomes the problem in certain circumstances where the EDI (Electronic Data Interchange) exchange does not work.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.164-164
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• 2011

최근들어 교량 건설 프로젝트는 그 규모가 방대해 졌을 뿐만아니라, 건설에 사용되는 장비 및 자재, 인력의 종류 또한 다양해 지고 있다. 이에 따라 종래 구조적 안전만을 추구하던 건설현장은 이러한 제반 요소들을 효율적으로 관리하여 경제성뿐만 아니라 시공의 효율성 까지 고려할 수밖에 없게 되었다. 따라서 건설 현장의 진도 및 자재, 인력관리는 현대 건설 산업의 주요 과제라 할 수 있다. 이에 따라 본 연구에서는 현장의 시공정보를 무선으로 송신할 수 있는 단말기 및 RFID를 이용하여 종래에 시행되던 작업을 자동화함으로써 작업의 편리성을 도모하고 이를 통하여 시간과 인력의 낭비를 줄일 수 있는 시공관리 시스템에 대한 모듈을 제안 하였다. 제안된 시스템은 3D모델을 기반으로 하여 진도 및 공비를 한눈에 알아볼 수 있는 방안을 제시한다. 사용자는 현재 진행되고 있는 공정을 3차원 모델에서 확인할 수 있으며, 현재까지 사용된 비용 및 공정률을 손쉽게 확인할 수 있다. 3D모델은 공사 시작 전 공정에 맞추어 분절된 형태로 제작되어 현장에서 송신한 위치정보가 통합관리 시스템에서 수신되면 해당 새그가 화면에 나타나게 된다. 3D모델은 공정시각화의 역할을 할 뿐만 아니라 각 새그에는 사용된 자재의 종류나 수량등이 DB화 되어 있어, 실시간으로 공사에 사용된 물량을 산출 할수 있도록 한다. 시공정보의 수신은 각 자재에 부착한 RFID태그를 직접 읽어서 송신하거나, 작업자가 시공상황을 단말기를 통하여 직점 송신함으로써 이루어지게 된다. 수집된 시공정보는 3D모델과 연계됨과 동시에 통합관리 시스템에 내장된 DB와 연결되어 사용 자재 및 물량에 대한 비용산출에 중요한 역할을 하게 된다. 현재 우리나라의 교량 시공 현장에서는 기성청구시 내역서를 기준으로 비용을 산정하게 되는데, 시공관리 통합 프로그램에서는 각 공정이 DB화된 내역서와 연계되어 3D모델에서 얻어진 물량으로 공비를 산출하는 과정이 자동으로 이루어지게 된다. 이러한 과정은 단일 현장뿐만 아니라, 공구 내의 여러 교량 현장에 대하여도 적용이 가능하므로, 방대한 현장의 공사관리에 소요되던 시간과 노력을 절감 할 수 있다. 본 연구를 통하여 현장에서 이루어지는 공사관리 작업에 대해 IT기술을 접목하여 자동화 할 수 있는 방법에 대한 알고리즘을 제시하였다. 이는 모바일 오피스 및 단말기를 이용하여 현 공정까지 사용된 물량, 인력, 장비 정보를 관리하는 한편, 현재까지 진행된 공사 내용을 3D모델을 통하여 한눈에 알아볼수 있는 교량 건설현장 통합관리 시스템의 모듈을 제공한다. 이에따라 공무 작업에 소모되는 인력 및 시간을 크게 절약 할 수 있을 것이라 판단된다.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.93-93
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• 2011

연육 연도교에 주로 건설되는 초장대교량은 시설물 특성상 이용객들의 대피공간이 제약받고 태풍, 해일 등 자연재해에 노출이 많기 때문에 다른 공공시설물보다 재난에 취약한 구조물이다. 최근 공공시설물의 건설동향이 구조물의 장대화로 되어감에 따라 재난 발생시 예상 위험이 점점 더 커져가고 있다. 본 연구는 이전 연구를 통해서 구축된 재난관리 시나리오를 토대로 재난관리 알고리즘을 개발하였다. 초장대교량의 재난은 자연재해와 인적재해로 구분할 수 있다. 여러 가지 재해 중 본 연구에서 제시한 재난관리 알고리즘은 자연재해의 경우 안개, 강설, 결빙, 강풍, 지진, 해일 및 풍수해이며 인적재해의 경우 화재, 교통사고, 구조물파괴 및 테러이다. 이 재난관리 알고리즘은 재난관리 전산 프로그램 구축의 기초로 사용될 것이다. 본 연구는 국내외 재난관리 관련 사례조사를 토대로 재난 수준별 평가방법을 수립하였다. 안개, 강설, 결빙, 강풍, 지진, 해일 및 풍수해와 같은 자연재난은 심각한 재난 발생전에 교통통제가 가능한 형태로 분류될 수 있으며 사례조사를 통해 교통통제 관리기준을 설정하였다. 화재, 교통사고, 구조물 파괴 및 테러와 같은 인적재난은 상황 발생시부터 비상대응을 취해야할 재난의 형태로 분류될 수 있으며 사고발생 시나리오를 통해 대응 단계별 평가방법을 설정하였다. 또한 재난 수준별 평가방법을 토대로 재난관리 알고리즘을 개발하였다. 자연재해와 같이 사고 발생 전에 교통통제가 가능한 재해는 교통통제 모듈로 구분하여 재난관리 알고리즘을 설정하였다. 인적재해와 같이 사고 발생 즉시 비상대응을 실시해야할 재해는 비상대응 모듈로 구분하여 재난관리 알고리즘을 설정하였다. 교통통제 모듈과 비상대응 모듈은 원칙적으로 국가재난관리등급에 따라 관심, 주의, 경계, 심각의 4단계로 구분하였다. 교통통제 모듈과 비상대응 모듈은 AAD에 의해 관리자, 외부기관 및 이용자 각각의 세부 행동지침 및 요령을 제시하였다.

• Journal of Industrial Convergence
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• v.18 no.1
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• pp.97-107
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• 2020

Since long ago, there has been a saying that "Drink water to quench thirst, drink alcohol to remove anguish and anxiety, and drink tea to recover from fatigue and refresh mind." Tea is really better for body and mind than water when it is drunken long and is valuable Jinda(眞茶) given by mother nature. In particular, curing tea reflecting characteristics of climate changes in all seasons helps in keeping health. Since tea contains the Yin-Yang system, which is a philosophical ideology of ancient people, old predecessors knew which tea they should brew and drink for curing in harmony with Yin and Yang. As a factor that influences component changes of tea, a complex interaction of heaven, earth and man is important and especially, mind of a person to handle tea is most important. Tea is a natural curing drink, which plays a role as a bridge between humans and nature.

• Journal of Information Technology Services
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• v.20 no.4
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• pp.129-140
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• 2021

Recently, interest in AI tutors is rising as a way to bridge the educational gap in school settings. However, research confirming the effectiveness of AI tutors is lacking. The purpose of this study is to explore how effective learner characteristics and recommended item learning activities are in predicting learner's academic performance in an adaptive online learning environment. This study proposed the hypothesis that learner characteristics (prior knowledge, midterm evaluation) and recommended item learning activities (learning time, correct answer check, incorrect answer correction, satisfaction, correct answer rate) predict academic achievement. In order to verify the hypothesis, the data of 362 learners were analyzed by collecting data from the learning management system (LMS) from the perspective of learning analytics. For data analysis, regression analysis was performed using the regsubset function provided by the leaps package of the R program. The results of analyses showed that prior knowledge, midterm evaluation, correct answer confirmation, incorrect answer correction, and satisfaction had a positive effect on academic performance, but learning time had a negative effect on academic performance. On the other hand, the percentage of correct answers did not have a significant effect on academic performance. The results of this study suggest that recommended item learning activities, which mean behavioral indicators of interaction with AI tutors, are important in the learning process stage to increase academic performance in an adaptive online learning environment.

• Journal of Intelligence and Information Systems
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• v.18 no.3
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• pp.153-169
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• 2012

Exhibitions have played a key role of effective marketing activity which directly informs services and products to current and potential customers. Through participating in exhibitions, exhibitors have got the opportunity to make face-to-face contact so that they can secure the market share and improve their corporate images. According to this economic importance of exhibitions, show organizers try to adopt a new IT technology for improving their performance, and researchers have also studied services which can improve the satisfaction of visitors through analyzing visit patterns of visitors. Especially, as smart technologies make them monitor activities of visitors in real-time, they have considered booth recommender systems which infer preference of visitors and recommender proper service to them like on-line environment. However, while there are many studies which can improve their performance in the side of new technological development, they have not considered the choice factor of visitors for booth recommender systems. That is, studies for factors which can influence the development direction and effective diffusion of these systems are insufficient. Most of prior studies for the acceptance of new technologies and the continuous intention of use have adopted Technology Acceptance Model (TAM) and Extended Technology Acceptance Model (ETAM). Booth recommender systems may not be new technology because they are similar with commercial recommender systems such as book recommender systems, in the smart exhibition environment, they can be considered new technology. However, for considering the smart exhibition environment beyond TAM, measurements for the intention of reuse should focus on how booth recommender systems can provide correct information to visitors. In this study, through literature reviews, we draw factors which can influence the satisfaction and reuse intention of visitors for booth recommender systems, and design a model to forecast adaptation of visitors for booth recommendation in the exhibition environment. For these purposes, we conduct a survey for visitors who attended DMC Culture Open in November 2011 and experienced booth recommender systems using own smart phone, and examine hypothesis by regression analysis. As a result, factors which can influence the satisfaction of visitors for booth recommender systems are the effectiveness, perceived ease of use, argument quality, serendipity, and so on. Moreover, the satisfaction for booth recommender systems has a positive relationship with the development of reuse intention. For these results, we have some insights for booth recommender systems in the smart exhibition environment. First, this study gives shape to important factors which are considered when they establish strategies which induce visitors to consistently use booth recommender systems. Recently, although show organizers try to improve their performances using new IT technologies, their visitors have not felt the satisfaction from these efforts. At this point, this study can help them to provide services which can improve the satisfaction of visitors and make them last relationship with visitors. On the other hands, this study suggests that they managers along the using time of booth recommender systems. For example, in the early stage of the adoption, they should focus on the argument quality, perceived ease of use, and serendipity, so that improve the acceptance of booth recommender systems. After these stages, they should bridge the differences between expectation and perception for booth recommender systems, and lead continuous uses of visitors. However, this study has some limitations. We only use four factors which can influence the satisfaction of visitors. Therefore, we should development our model to consider important additional factors. And the exhibition in our experiments has small number of booths so that visitors may not need to booth recommender systems. In the future study, we will conduct experiments in the exhibition environment which has a larger scale.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.6
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• pp.131-138
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• 2014

The steel structure fabrication plant certification program was enacted as a part of the construction technology management act, article 24-3, to improve the quality of steel construction after the decay falling accident of Seongsu Bridge in 1994. However, the national certification program for structural precast concrete that is a prefabricated construction products produced by casting concrete in plant is not implemented yet. So, to introduce the proper certification system for precast concrete, the quality certification programs of North America, Europe and Japan are surveyed. In North America, the organizations that manage the plant certification programs are PCI, NPCA, CPCI and so on. Sales of precast concrete elements in Europe are governed by the construction products regulation 305/2011. Therefore, CE marking is mandatory from July 2013 for all construction products including precast concrete. In Japan, precast concrete products used in civil engineering are certificated by JIS mark, product certification system and plants for manufacturing precast concrete building elements are audited by Japan Prefabricated Construction Suppliers and Manufacturers Association. Based on these survey studies, in this paper is described an adaptation of precast concrete plant certification to comport with the certification system in Korea.

• Journal of the Korean Institute of Landscape Architecture
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• v.52 no.4
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• pp.86-103
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• 2024

This study interprets the evolving ideologies of Singapore's urban environmental policies focusing on the meanings encapsulated within the notion of 'garden'. Through a comprehensive review of policy documents, legislative materials, development projects, government promotional materials, and organizational changes in each era, the study identifies three phases, each with distinct central themes. Commencing in the 1960s, the initial phase projected a meticulously controlled and managed cityscape using the notion of garden, which was epitomized by the slogan 'Garden City'. In this phase, garden was a representative concept that embodied the cleanliness and greenness of the city, and also served as a strategic rhetoric to effectively transfer the ideology of an exemplary picturesque city to the public. Subsequently, in the 1970s, the focus gradually shifted from individual green spaces and bodies of water towards a collective system which served as a foundational infrastructure of the city-nation. This evolution was reflected in the new slogan 'City in a Garden', where the garden is now not only summoned for its external appearance but also as an unified system which serves as the cornerstone of the city. Through these phases, the Singaporean government developed a scheme capable of integrated management of green spaces and water resources tailored to the scale and function of each. Building upon this foundation, the early 2000s saw the adoption of a new orientation focusing on sustainability and urban ecology, encapsulated in the revised slogan 'City in Nature'. For more than five decades, Singapore has demonstrated an adept utilization of the notion 'garden'. This scholarly examination underscores Singapore's journey in redefining urban landscapes through the strategic employment of the concept of garden in its urban environmental policies. By tracing the evolution of the garden concept across distinct phases, the study illuminates how the Singaporean government leveraged the garden's versatility: from an effective metaphor of aesthetic values to an integral component of its holistic urban system, and finally to a bridge between the urban and the natural.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.5
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• pp.144-155
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• 2022

The Korea Coast Guard evaluates the risk of major coastal activity places to prevent coastal accidents, and patrols and manages them based on that, but it is not responding properly to the continuously increasing number of coastal accidents. The reason for this is that, despite the gradual expansion of coastal activity places, there is a lack of manpower to manage and supervise them, resulting in blind spots in coastal accident safety management. Therefore, in order to solve this problem, it is necessary to prepare more efficient and effective measures that check and supplement the current coastal safety management system. Coastal accidents show different characteristics of accident causes and places due to differences in the activity characteristics of users according to time. As a result of analyzing coastal accident data (2017~2021), the frequency of daytime accidents is high in the case of sea rock, beach, and offshore, where family leisure activities are frequent. In the case of wharf, tidal flat and bridge, where accidents due to drinking, disorientation, and suicide mainly occur, the frequency of accidents at night is high. In addition, there were more accidents on weekends when the number of users increased compared to weekdays. This trend indicates that the user's temporal activity characteristics must be reflected in the risk assessment of coastal activity places. Therefore, in this study, based on the case of coastal accidents, the characteristics of accidents at coastal activity places according to time were identified, and the criteria were presented for risk evaluation by grading them. It is expected that it will be possible to lay the foundation for reducing coastal accidents by efficiently managing and supervising coastal activity places over time using the presented evaluation criteria.