• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.550-558
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• 2018

This paper presents the current limit strategy of voltage controller of delta-connected H-bridge static synchronous compensator (STATCOM) under an unbalanced voltage fault event. When phase to ground fault happens, the feasibility to heighten the magnitude of sagging phase voltage is considered by using symmetric transformation method in delta-structure STATCOM. And the efficiency to cover the maximum physical current limit of switching device is considered by using vector analysis method that calculate the zero sequence current for balancing the cluster energy in delta connected H-bridge STATCOM. The result is simple and obvious. Only positive sequence current has to be used to support the unbalanced voltage sag. Although the relationship between combination of the negative sequence voltage with current and zero sequence current is nonlinear, the more negative sequence current is supplying, the larger zero sequence current is required. From the full-model STATCOM system simulation, zero sequence current demand is identified according to a ratio of positive and negative sequence compensating current. When only positive sequence current support voltage sag, the least zero sequence current is needed.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2019년도 추계학술발표대회
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• pp.585-588
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• 2019

Predictions of Energy Consumption for Industries gain an important place in energy management and control system, as there are dynamic and seasonal changes in the demand and supply of energy. This paper presents and discusses the predictive models for energy consumption of the steel industry. Data used includes lagging and leading current reactive power, lagging and leading current power factor, carbon dioxide (tCO2) emission and load type. In the test set, four statistical models are trained and evaluated: (a) Linear regression (LR), (b) Support Vector Machine with radial kernel (SVM RBF), (c) Gradient Boosting Machine (GBM), (d) random forest (RF). Root Mean Squared Error (RMSE), Mean Absolute Error (MAE) and Mean Absolute Percentage Error (MAPE) are used to measure the prediction efficiency of regression designs. When using all the predictors, the best model RF can provide RMSE value 7.33 in the test set.

• 스마트미디어저널
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• 제12권1호
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• pp.92-101
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• 2023

현재 실감 콘텐츠에 대한 소비자 욕구가 증대하여 고화질 영상에 대한 중요성이 높아지므로, 본 연구는 지상파 방송사의 UHD 전략을 글로벌 경쟁력 확보를 위한 차원에서 제시하였다. 첫째, 실무적 전략으로, 견고한 내수시장 확보를 위해 각 부서간 협력을 통한 생태계 확보에 주력, 시너지를 창출하고, 글로벌 경쟁력을 갖추기 위한 UHD 분야에 우선순위를 두고 해당 분야의 강국과 긴밀한 협조체제의 필요, 우리나라 사회 문화적 실정을 고려한 가성비에 주목한 UHDTV 개발로 내수시장 확보 후 이를 통한 재정, 기술력 등으로 글로벌 시장 개발을 추진해야 함을 제시했다. 둘째, 정부는 글로벌 콘텐츠 강화를 위한 컨트롤타워 역할, 장기적 로드맵 구성, 관련 자료 지원과 우리나라만의 UHDTV 성과 모델을 만들어 해외에 적극 수출함으로써 글로벌 경쟁력 증대를 지원해야 함을 강조했다.

• 정보처리학회논문지:소프트웨어 및 데이터공학
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• 제9권5호
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• pp.153-160
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• 2020

산업용 에너지 소비 예측은 에너지 수요와 공급에 동적이고 계절적인 변화가 있기 때문에 에너지 관리 및 제어 시스템에서 중요한 위치를 차지한다. 본 논문은 철강 산업의 에너지 소비 예측 모델을 제시하고 논의한다. 사용되는 데이터에는 후행 및 선도적인 전류 반응 전력, 후행 및 선도적인 전류 동력 계수, 이산화탄소(TCO2) 배출 및 부하 유형이 포함된다. 테스트 세트에서는 (a) 선형 회귀(LR), (b) 방사형 커널(SVM RBF), (c) Gradient Boosting Machine (GBM), (d) 무작위 포리스트(RF). 평균 제곱 오차(RMSE), 평균 절대 오차(MAE) 및 평균 절대 백분율 오차(ME)의 네 가지 통계 모델을 사용하여 예측하고 평가한다. 회귀 설계의 효율성 모든 예측 변수를 사용할 때 최상의 모델 RF는 테스트 세트에서 RMSE 값 7.33을 제공할 수 있다.

• 한국정보과학회논문지:데이타베이스
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• 제31권4호
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• pp.422-431
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• 2004

최근에 이동 컴퓨팅 환경에서 여러 데이타 전송 모델이 연구되고 있다. 특히 서버가 반복적으로 필요한 정보를 전파해주는 주기적 푸시 모델에 대한 연구가 활발히 진행되고 있다. 그러나 데이타 평균 대기 시간은 브로드캐스트 한 주기의 길이에 상당히 영향을 받으며, 또한 여러 사용자들간의 접근 데이타가 차이가 날 경우 응답시간에 상당히 나빠질 수 있다. 이 경우, 그 사용자들은 차라리 서버에게 명시적으로 데이타를 요청하기를 바랄 것이다. 이러한 두 가지 접근방식을 모두 지원하는 것을 복합 브로드캐스트라고 한다. 이 환경에서, 본 논문에서는 새로운 이동 트랜잭션 처리 알고리즘(O-PreH)을 개발하였다. 우선 서버가 관리하는 데이타는 주기적 브로드캐스트 방식으로 처리되는 Push_Data와 요구-처리방식으로 처리되는 Pull_Data로 나뉘어 진다. 즉, 사용자는 요구하는 데이타의 타입에 따라 접근하는 방식이 차이가 난다. 또한 서버는 이동 트랜잭션 일관성 유지를 돕기 위해 주기적으로 무효화 보고를 전송해준다. 만약 사용자가 무효화 보고에 의해 하나 이상의 충돌을 발견한다면, 일관성을 침해하지 않는 범위 내에서 그 충돌 순서를 결정한 후(pre-reordering) 나머지 연산들을 비관적으로 수행시킨다. 자세한 실험 과정을 거쳐 제안한 알고리즘의 성능 향상을 보였다.

• 한국GIS학회:학술대회논문집
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• 한국GIS학회 1995년도 추계학술대회 발표요약문
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• pp.9-21
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• 1995

계획지원체계는 도시성장관리수단으로 간선시설 시설확장을 이용하는 우리의 능력을 증진시킨다. 이연구는 그러한 계획지원체계 (PEGASUS: 공간도시체계의 생성 및 분석을 위한 계획환경)의 개발계획의 일환으로서 상수도 시설확장모델의 개발에 관한 연구이다. 이 연구는 토지이용과 개발은 간선시설의 수요를 유발하고 간선시설은 토지가 이용되고 개발되는 방향에 영향을 미친다는 전제하에서 시작된다. 상수도 시설 확장은 2 방법으로 해결될 수 있다: 1) 최적통제이론, 2) MINLP 방법. 이 방법들은 각각장단점을 가지고 있다. 이 연구에서는 동적 시설 확장 크기 및 시기를 동시에 결정할 수 있는 MINLP방법이 채택이 되었다. 상수도 관망해석모델과 동적 상수도 시설 최적화 모델이 상수도계획과 토지이용계획의 동적 연관관계를 해결할 수 있다. 상수도 관망해석모델은 생성된 관경의 적정성을 분석하며 동적 상수도 시설 최적화모델은 변화하는 상수도 수요량을 충족할 수 있는 대안을 작성한다. 표준화기법에 의한 비용편익분석은 가장 경제적인 대안을 선정한다. GIS는 필요 상수도 수요량을 산정하고 시설확장모델의 결과를 이용자에게 보여주는데 훌륭한 역활을 할 수 있다.

• Transactions on Control, Automation and Systems Engineering
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• 제3권3호
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• pp.181-189
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• 2001

The software components of embedded control systems get extremely complex as they are designed into distributed systems get extremely complex as they are designed into distributed systems consisting of a large number of inexpensive microcontrollers interconnected by low-bandwidth real-time networks such as the controller area network (CAN). While recently emerging middleware technologies such as CORBA and DCOM address the complexity of distributed programming, they cannot be directly applied to distributed control system design due to their excessive resource demand and inadequate communication models. In this paper, we propose a CORBA-based middleware design for CAN-based distributed embedded control systems. Our design goal is to minimize its resource need and make it support group communication without losing the IDL (interface definition language) level compliance to the OMG standards. To achieve this, we develop a transport protocol on the CAN and a group communication scheme based on the well-known publisher/subscriber model. The protocol effectively realizes subject-based addressing and supports anonymous publisher/subscriber communication. We also customize the method invocation and message passing protocol, referred to as the general inter-ORB protocol (GIOP), of CORBA so that CORBA method invocations are efficiently serviced on a low-bandwidth network such as the CAN. This customization includes packed data encoding and variable-length integer encoding for compact representation of IDL data types. We have implemented our CORBA-based middleware on the mArx real-time operating system we have developed at Seoul National University. Our experiments clearly demonstrate that it is feasible to use CORBA in developing distributed embedded control systems possessing severe resource limitations. Our design clearly demonstrates that it is feasible to use a CORBA-based middleware in developing distributed embedded systems on real-time networks possessing severe resource limitations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권11호
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• pp.5301-5323
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• 2017

Small cell deployment offers a low-cost solution for the boosted traffic demand in heterogeneous cellular networks (HCNs). Besides improved spatial spectrum efficiency and energy efficiency, future HCNs are also featured with the trend of network architecture convergence and feasibility for flexible mobile applications. To achieve these goals, dual connectivity (DC) is playing a more and more important role to support control/user-plane splitting, which enables maintaining fixed control channel connections for reliability. In this paper, we develop a tractable framework for the downlink SINR analysis of DC assisted HCN. Based on stochastic geometry model, the data-control joint coverage probabilities under multi-frequency and single-frequency tiering are derived, which involve quick integrals and admit simple closed-forms in special cases. Monte Carlo simulations confirm the accuracy of the expressions. It is observed that the increase in mobility robustness of DC is at the price of control channel SINR degradation. This degradation severely worsens the joint coverage performance under single-frequency tiering, proving multi-frequency tiering a more feasible networking scheme to utilize the advantage of DC effectively. Moreover, the joint coverage probability can be maximized by adjusting the density ratio of small cell and macro cell eNBs under multi-frequency tiering, though changing cell association bias has little impact on the level of the maximal coverage performance.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2015년도 학술발표회
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• pp.216-216
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• 2015

Frequent hydro-meteorological events caused by global climate change and human exacerbate activities, make the water resource problem more complicated. The increasing speed urbanization brings a significant impact on the city flood control and security, water supply safety, water ecological security, water environment safety and the water engineering security in China, and puts forward higher requirements to urban water integrated management, undoubtedly which become the biggest obstacle for water ecological civilization construction, thus urgent requiring an advanced methods to enhance the effectiveness of the water integrated management. The other fields of smart ideas point out a development path for water resource development. The construction demand of smart water resource is expounded in the paper, combining the philosophy of modern Internet of things with the application of cloud computing technology. The concept of smart water resource is analyzed, the connotation characteristics of smart water resource is extracted, and the general model of smart water resource is refined. Then, the frame structure of smart water resource is put forward. The connotation and the overall framework of the smart water resource represent a higher level of water resource informationization development and provide a comprehensive scientific and technological support to transform water resource management from an extensive, passive, static, branch and traditional management to a fine, active, dynamic, collaborative and modern management.

• Asia Marketing Journal
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• 제15권2호
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• pp.49-73
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• 2013

In this study, the author develops and tests a model that incorporates the mediating effects of two frontline employee psychological variables (emotional exhaustion and intrinsic motivation) based on job demand and resource model. As a form of environmental resource, person-organization fit was proposed as a leading factor of frontline employee boundary spanning behavior through emotional exhaustion and intrinsic motivation. All measures were adapted from or developed based on prior research. Data for the study were collected from a cross-sectional sample of retail bank employees in South Korea. Questionnaires were distributed to 500 frontline employees across several banks. Of these, 322 usable questionnaires were returned. To analyze the data, a structural equation model procedure using LISREL 8.5 was employed. Results show that an employee's perceived fit with his/her organization enhances intrinsic motivation and reduces emotional exhaustion. These mechanisms, in turn, increase the employee's boundary spanning behavior. These results support the notion that person-organization fit should be one of the factors affecting motivation, affect and attachment, and extends such an understanding to a purely service-based environment among customer contact employees. Results also confirms that P-O fit can be viewed as environmental resources, and the JD-R model provides a theoretical base in further studying the antecedent role of P-O fit on frontline employees's boundary spanning behavior through intrinsic motivation and emotional exhaustion. These results suggest that organizations have to do their best to manage P-O fit, be it through employee screening or training and workshops to try and align organization and employee values and objectives. If managers of organizations are positively evaluated by the employees, it will be easier for them to, give things of value to employees, such as sense of direction, values, and recognition, and receive other things in return such as esteem and responsiveness. Consequently, organizational leaders are not only able to manage employee experiences, but also their fit with the organization. Even if a manager cannot control employee P-O fit, this research suggests, that a focus on reducing emotional exhaustion rather than increasing intrinsic motivation seems optimal. This research also supports the idea that motivation has a direct association with a frontline employee's boundary spanning behavior. Even in situations where emotional exhaustion cannot be reduced, organizations may still influence frontline behaviors through motivation.