• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1193-1194
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• 2011

We performed commissioning of redundant digital excitation system for gas turbine generator. One of its issues is first power supply test to gird line when it was compared with the other commissioning. If blackout will be happened, a few of start power plants must supply power to grid line. And then generator must increase voltage and real power slowly for line charge. The trial product was installed and successfully operated at a 100MW power plant after commissioning.

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.230-233
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• 2003

Simulation model of induction type fixed speed wind power generator is developed. It is shown that the peak value of inrush current during start up changes according to the firing angle control strategy of soft starter. New proposed firing angle control scheme showed $25\%$ of reduction of peak current which results in smaller drop of gird voltage at the point of common coupling during start up.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.30 no.3
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• pp.313-323
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• 2020

With the development of smart grid technologies, a user can use the secure and reliable power services in smart gird environments. However, the users are not secure against various potential attacks because the smart gird services are provided through the public channel. Therefore, a secure and lightweight authentication and key agreement scheme has become a very important security issue in smart grid in order to guarantee user's privacy. In 2019, Zhang et al. proposed a lightweight authentication scheme for smart gird communications. In this paper, we demonstrate that Zhang et al.'s scheme is vulnerable to impersonation and session key disclosure attacks, and then we propose a secure authentication and key agreement scheme for smart grid environments without tamper-resistant devices. Moreover, we perform the informal security and the BAN logic analysis to prove that our scheme is secure various attacks and provides secure mutual authentication, respectively. We also perform the performance analysis compared with related schemes. Therefore, the proposed scheme is efficiently applicable to practical smart gird environments.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.28 no.3
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• pp.33-40
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• 2022

Background: The cross-body and the sleeper stretches have been used to improve posterior shoulder tightness (PST). However, such stretching techniques may not always help achieve scapular stability and may even aggravate patient's symptoms. Therefore, a new stretching technique (passive glenohumeral internal rotation with bridging) was developed as a more effective method that may allow for greater scapular stability without aggravating the symptoms. Thus, this study aimed to examine and compare this novel stretching technique to determine its effect on the range of motion (ROM) and acromio-humeral distance (AHD) in patients with glenohumeral internal rotation deficits (GIRD) with posterior shoulder tightness. Methods: A total of 30 symptomatic patients with asymmetrical GIRD were randomly assigned to two groups: the novel stretching group (n=15) and the joint mobilization group (n=15). The intervention was conducted twice a week for a total of four weeks. The ROM of shoulder internal rotation was measured by a goniometer and the AHD was evaluated by an X-ray before and after the intervention. Results: Both the treatments improved ROM and AHD in patients with GIRD (p<.05). However, the improvements in internal rotation ROM and AHD in the novel stretching group were significantly greater than that of the subjects in the mobilization group. There was a significant difference between the two groups (p<.05). Conclusion: These results show that both novel stretching and joint mobilization improved ROM and AHD in patients with GIRD with PST. However, novel stretching was more effective than joint mobilization.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1064-1070
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• 2007

This paper presents a grid-interactive current controlled voltage source inverter (CCVSI) with uniterruptible power supply (UPS), which uses an inner current control loop (polarized ramp time (PRT)) and outer feedback control loops to improve grid power quality and UPS. To reduce the complexity, cost and number of power conversions, which results in higher efficiency, a single stage CCVSI is used. The operation of this system could be divided into the power quality control (PQC) state mode and the UPS state mode. In PQC mode, the system operated to compensate the reactive power demand by nonlinear load or variation in load. In UPS mode. the system is controlled to provide a sinusoidal voltage at the rated value for the load when the gird fail. To verify the proposed system, a comprehensive evaluation with theoretical analysis, simulation and experimental results for 1KVA load capacity is presented.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1788-1790
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• 2005

In this paper, an operating characteristics of a 50 kW gird-connected photovoltaic(PV) power system was analysed from 2000 to 2004. The construction of the PV system includes a 3-phase inverter for grid connection, PV module, distribution box, and data monitoring system. The major results of the demonstration test of the 50 kW class gird-connected PV system showed that efficiency of PV system was 11.13%, and the conversion efficiency of the inverter was 92% at a 50% load.

• 한국전산유체공학회:학술대회논문집
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• 1996.05a
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• pp.118-124
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• 1996

When computing the flow around complex three dimensional configurations, the generation of the grid is the most time consuming. This paper presents a survey of the grid generation technique. The technique for treating problems arising in gird generation for complex geometries is addressed. A general procedure for generating boundary conforming grids is included

• Journal of the Korean GEO-environmental Society
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• v.25 no.1
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• pp.5-11
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• 2024

Ground subsidence mainly occurs in urban areas with high population density, so it is necessary to clearly identify the cause of occurrence and prepare in advance. The main cause of ground subsidence is reported to be the creation of cavities in the ground due to damage to underground pipes, but the property information and influencing factors of underground pipes to predict and prepare for ground subsidence are not properly established. Therefore, in this study, factors showing a significant correlation with the occurrence of ground subsidence were selected among the underground facility property information and a regression equation was proposed through logistic regression analysis. For this purpose, data on underground structures and ground subsidence history information in the target area were collected, and the target area was divided into girds of 100m x 100m in size using QGIS. The underground facility attribute information and ground subsidence history information contained within the gird were extracted. Then, preprocessing was performed to construct a dataset and correlation analysis was performed. As a result, factors excluding the year of sewer pipes and communication pipes and the average depth of communication pipes, heat pipes, and gas pipes were found to have a significant correlation with ground subsidence. In addition, a regression equation for whether ground subsidence occurred in the target area is proposed through logistic regression analysis.

• 한국전산유체공학회:학술대회논문집
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• 2001.10a
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• pp.174-181
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• 2001

The Gird is a communication service that collaborates dispersed high performance computers, large-scale databases and modern equipments so that those can be shared and worked together. In this paper. CFD research based on National Grid project is discussed. To validate the Grid technology, the flow past ONERA M6 wing and the flow past infinite wing are simulated on the National Grid testbed.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1999.06a
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• pp.99-104
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• 1999

화재 진압시스템 중 가장 대표적이고 많이 사용되는 설비는 스프링클러 시스템이다. 국내에 설치되고있는 스프링클러 시스템은 많은 문제점을 가지고 있으며 특히 배관방식과 설계부분이 그러하다. 지금까지의 국내의 스프링클러 시스템 설계는 규약배관방식만으로 이루어졌으며, 최근에 수리계산 방식의 인정이 법제화되어 사용이 늘어날 전망이지만, 이미 선진외국은 오래 전부터 수리계산방식을 사용하고 있으며, 급속히 발전되고있는 컴퓨터 프로그램을 이용한 수리계산 설계를 시행하고 있다. 특히 선진국에서는 국내에서는 사용하지 않고 있는 격자배관 방식(Gird System)을 사용하고 있는데 이는 컴퓨터 프로그램에 의한 설계로만 가능하다. (중략)