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동기발전기 동요 특성을 고려한 전력계통 안정화 장치에 대한 연구
김종주(Jongju Kim),이흥석(Heungseok Lee),이화석(Hwaseok Lee),김형수(Hyungsoo Kim),박준호(June Ho Park) 대한전기학회 2021 대한전기학회 학술대회 논문집 Vol.2021 No.4
본 논문에서는 동기발전기의 동기임피던스 특성을 활용하여 회전자의 저주파 진동에 대한 제동력을 향상시킨 전력계통 안정화 장치(PSS)를 제안한다. 동기임피던스의 변화와 동요의 크기를 관계를 통해 PSS가 안정화 신호를 추가 공급하도록 하는 구조로 설계되었다. 제안하는 PSS에 대한 성능검증을 위해서 발전기-여자기-PSS(GEP)모델과 Single Machine Infinite Bus (SMIB)모델을 활용한 주파수영역 분석, 그리고 MATLAB /Simulink를 활용하여 구성한 동기발전기 4기 계통에 적용하여 시뮬레이션을 수행하였다.
소프트웨어프리랜서의 경력몰입이 프로젝트 중도 포기 의도에 미치는 영향에 관한 연구: 조직몰입의 매개효과와 경력기간의 조절효과
이종주(Lee Jongju),오인하(Oh Inha) 한국혁신학회 2021 한국혁신학회지 Vol.16 No.4
4차 산업혁명, 긱 이코노미(gig economy)로 인해 새로운 일자리로 프리랜서가 주목받고 있다. 이러한 변화의 기반인 소프트웨어 산업도 프리랜서의 역할과 규모가 증가하고 있는 것으로 보인다. 소프트웨어 기업의 사용자는 개발 프로젝트에서 소프트웨어프리랜서를 통해서 이윤을 창출하고 있지만, 사용자는 프리랜서에 대한 인적자원관리 방안이 없어서 어려움을 겪고 있다. 본 연구는 이를 해결하기 위해서 소프트웨어프리랜서 대상의 총 250부의 설문을 활용해 이들의 프로젝트 중도 포기를 낮추는 방안에 대해 구조방정식 모형 분석을 하였고, 다음과 같은 결과를 얻었다. 첫째, 소프트웨어프리랜서의 경력몰입이 프로젝트 중도 포기의도에 영향을 미치지 않음을 확인하였다. 둘째 소프트웨어프리랜서의 경력몰입이 조직몰입에 유의한 영향을 미침을 확인하였다. 셋째, 소프트웨어프리랜서의 조직몰입이 프로젝트 중도 포기의도에 유의한 영향을 미침을 확인하였다. 넷째, 소프트웨어프리랜서의 경력몰입이 조직몰입을 매개하여 프로젝트 중도 포기의도에 영향을 미침을 확인하였다. 다섯째, 소프트웨어프리랜서의 경력몰입과 조직몰입 사이에서 프리랜서 활동 경력기간의 유의한 조절효과를 확인하였다. 본 연구는 소프트웨어프리랜서가 프로젝트를 완수하게 하려면 조직몰입이 중요한 요소임을 확인하였고, 프리랜서로 활동한 경력기간에 따라 조직몰입이 달라짐을 밝혔다. 소프트웨어프리랜서의 조직몰입을 관리한다면 사용자의 프로젝트 성공률을 높이는데 도움이 될 것이다. Freelancers are attracting attention for new jobs due to the 4th industrial revolution and the gig economy. In the SW industry, the role and size of freelancers appears to be increasing. Employers of SW companies are making profits through SW freelancers in development projects, but employers are having difficulties in managing human resources of freelancers. In order to solve this problem, this study conducted a structural equation model analysis on how to lower their project abandonment by using a total of 250 questionnaires for SW freelancers, and the following results were obtained. First, their career commitment does not significantly affect their intention to give up on a project. Second, their career commitment has a significant effect on organizational commitment. Third, their organizational commitment has a significant effect on their intention to give up on a project. Fourth, their career commitment mediates organizational commitment and significantly affects their intention to give up on a project. Fifth, between their career commitment and organizational commitment, the length of their freelance career had a significant moderating effect. This study confirmed that organizational commitment is an important factor for SW freelancers to complete their projects, and revealed that organizational commitment varies according to the length of their freelance career. Managing the organizational commitment of software freelancers will help increase the project success rate from the user"s point of view.
Kim Jongju,Lee Heungseok,Kim Sungshin,Park June Ho 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.4
This paper proposes a real-time transient stability prediction model based on neural networks. The proposed convolutional long short-term memory (C-LSTM), including convolution operation and recurrent network structure, effectively learns transient stability characteristics from multidimensional tensors of the power system and exhibits high-performance prediction in real-time. To construct the transient stability prediction model, the method of preprocessing the phasor measurement unit (PMU) data, the structural features of the C-LSTM, and the procedure of training neural networks are dealt with in detail. In the case study, the performance of the proposed model trained by the simulation data of the IEEE-39 bus system is evaluated through the confusion matrix. To verify the capability of the proposed model, the robustness against the noise and the relationship between the performance and the prediction time are analyzed.
Yun, Jongju,Lee, Cheesung,Zheng, Qing,Baik, Seunghyun American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.8
<P>We synthesized vertically-aligned multi-walled carbon nanotubes with an inner diameter of 1.6-7.5 nm and stack height of 80-28600 microm by chemical vapor deposition. The effects of synthesis conditions such as substrate position in the tube furnace, maximum temperature, temperature increasing rate and synthesis duration on the structure of nanotubes were investigated. It was found that slightly faster temperature increase rate resulted in significantly longer length, larger diameter and more defects of nanotubes. Structural parameters such as inner, outer diameters, wall thickness and defects were investigated using transmission electron microscopy and Raman spectroscopy.</P>
Extraordinary High Microwave Absorption Cross Section of Ultralong Carbon Nanotubes
Yun, Jongju,Jeon, Wonjae,Drahushuk, Lee W.,Baik, Seunghyun,Strano, Michael S. American Chemical Society 2014 The Journal of Physical Chemistry Part C Vol.118 No.25
<P>The microwave-induced heating of nanoparticles has been actively studied in pursuit of more efficient microwave absorbers. Here we systematically investigated the microwave absorption cross section of conductive particles (Al), magnetic particles (Fe<SUB>3</SUB>O<SUB>4</SUB>), and carbon nanotubes with different lengths. The particles were suspended in silicone oil and irradiated with a microwave at 2.45 GHz using a single-mode microwave reactor. The experimentally measured heating rate was analytically modeled based on the modified Lambert–Beer law to obtain the microwave absorption cross section per mass. The microwave-induced heating rate was primarily dependent on optical absorbance, which is proportional to the mass concentration of suspended particles. Under the similar optical absorbance, longer nanotubes provided greater microwave absorption cross section which could be described by the short dipole antenna theory. The microwave absorption cross section of 5 mm long multiwalled carbon nanotubes was ∼4080 times greater than that of Al particles. One-dimensional ultralong carbon nanotubes provide a unique opportunity as super microwave absorbers which may be useful in chemical, biomedical, and process applications.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2014/jpccck.2014.118.issue-25/jp500831c/production/images/medium/jp-2014-00831c_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp500831c'>ACS Electronic Supporting Info</A></P>