Modeling and Simulation about Long Term Dynamics Using Real Time Digital Simulator

Nam, Su-Chul,Song, Ji-Young,Lee, Jae-Gul,Shin, Jeong-Hoon,Kim, Tae-Kyun The Korean Institute of Electrical Engineers 2012 The Journal of International Council on Electrical Vol.2 No.4

RTDS (Real Time Digital Simulator) has several benefits. First, current power system simulation tool dose not simulate electromagnetic transient phenomenon, but it is possible using RTDS. Second, off-line electromagnetic transient simulation tools (EMTDC, PS-CAD, etc.) do not simulate real-time analysis, but RTDS is able to do real-time analysis. Third, RTDS is able to simulate related external devices those are protection relays, new developed control devices and power system devices. So many engineers use RTDS in power industry using these advantages of RTDS. KEPCO (Korea Electric Power Corporation) also use RTDS for developing new special protection scheme that is a new developed protection scheme for maintaining voltage stability in metropolitan area using real time synchro phasor data. Voltage stability phenomena of power system are divided three parts by time period. Those are transient, short term and long term voltage stability phenomena. Almost critical voltage stability problems happen in long term time period. Because power system devices and loads those influence voltage stability have long term dynamic characteristic. So if we want correct results of voltage stability analysis, then we have to analyze long term dynamic about voltage stability. Long term dynamic characteristic of voltage stability that is influenced by under voltage tap changer, over excite limiter, dynamic loads and so on. Unfortunately, we had not an analysis environment about long term dynamics for validating new control system. So this paper discusses about modeling and simulation of long term dynamics using RTDS. First, we build well known test system that consists of 2 generators and 11 buses using RTDS. Second, we model dynamic controllers and devices those are under load tap changer, over exciting limiter and dynamic load and we validate those dynamic characteristics. Those influence to long term voltage stability. Lastly, we simulate voltage collapse phenomena during long term time period using test-system include built long term dynamic models when occurring line fault.

Long-term Chemical Stability Study for I Waste-form Using TAB (Te-Ag-Bi) Matrix in Domestic Underground Water

Hyeon Jin Eom,Ki Rak Lee,Ga yeong Kim,Kyuchul Shin,Hwan-Seo Park 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.1

During the treatment of spent nuclear fuel, radioactive iodine is generated in a liquefied or gaseous form in a specific process. In the case of iodine 129, it is a long-lived nuclide with a very long halflife and has high groundwater mobility under repository conditions. Despite showing a low radioactivity value, research on the management of radioactive iodine from a long-term perspective is continuously being performed. Although research has been conducted using borosilicate glass as a medium for solidifying iodine, compatibility of I in borosilicate glass is very small and the volatility is high in the solidification process. So it is not suitable as a solidified substance of iodine. Therefore, studies on other solidification media to replace them are continuously being conducted. Our research team tried to develop a new medium that can contain iodine in a solidified body stably through a simple heat treatment process and can improve problems such as volatility and waste loading. Iodine is captured as AgI in the Ag ion-exchanged zeolite. So, TeO2, Ag2O, and Bi2O3 having a high AgI loading rate were used as main components. It was named TAB after taking the first letter of each element. In previous studies, the physical properties, structure, and chemical stability of TAB materials were confirmed. PCT (Product Consistent test) was performed to confirm chemical stability. It is mainly used to compare the chemical stability of glass materials with other glass materials, but there are limitations in evaluating the long-term chemical stability of materials. In this experiment, we tried to evaluate the long-term stability of TAB and compare it with borosilicate, which is conventionally used to treat radioactive waste. In addition, we tried to understand the leaching behavior inside the TAB medium. For this purpose, ASTM C1308 test was performed for 365 days, and distilled water and KURT groundwater were used as leachates to examine the effect of ions in the groundwater on the solidified body. To analyze the leaching behavior, ICP-MS and ICP-OES analyses were performed, and the cross-section of the sample after leaching was observed through SEM.

가속노화를 이용한 매칭젤 장기 저장 영향성 평가 연구

남준식 한국산학기술학회 2024 한국산학기술학회논문지 Vol.25 No.7

Refractive index matching gel(매칭젤)은 분리된 광통신 케이블의 접촉면에 사용되어 통신 신호 감쇄를 방지하는 소재이다. 매칭젤은 군수품에 사용되어 장비의 정상적인 통신 유지를 보장하기 위해 사용된다. 군수품은 상용품과는 다르게 30년 이상 장기간 저장되며 장기 저장된 이후에도 유사시 정상 작동이 요구된다. 따라서 매칭젤은 높은 수준의 장기 안정성이 요구된다. 매칭젤은 주로 광섬유와 굴절률이 유사하고 안정성이 높은 실리콘 오일 소재로 만들어진다. 안정성이 높은 소재들로 매칭젤이 만들어지지만, 현재까지 장기 안정성에 관한 연구는 미흡하였다. 이 논문에서는 매칭젤의 장기 저장 안정성을 평가하고자 하였다. 매칭젤의 장기 저장 상태를 가속 노화 실험을 이용해 모사하고, 모사된 저장 기간에 따른 매칭젤의 원소 함량, 화학 작용기의 비율 변화 및 굴절률 변화를 관찰하였다. 매칭젤은 최대 265년 저장 기간이 모사되었다. 장기 저장 후 원소 비율과 화학적 조성은 크게 변하지 않으나, 굴절률이 특정 저장 기간 이후부터 증가하는 것을 관찰하였다. 이 연구 결과를 활용하면 매칭젤이 사용된 군수품의 장기 저장에 따른 통신계통 정비 주기 정립에 도움이 되어 군수품 신뢰성 향상에 이바지할 것으로 기대된다. Refractive index matching gel is used on the contact surface of separated optical communication cables to prevent the attenuation of communication signals. The gel is composed primarily of silicone oil, which closely matches the refractive index of optical fibers. In military applications, matching gels ensure the proper equipment functioning and maintain efficient communication. Nevertheless, the materials used need to exhibit high stability because of the complexity of military equipment and the requirement for long-term stability. Research on the long-term stability of these gels has been insufficient. This study evaluated the long-term storage stability of the refractive index matching gel. Thermal accelerated aging experiments simulated a storage duration of up to 265 years. The study showed that the elemental and chemical compositions were similar after long-term storage. On the other hand, an increase in refractive index is observed after a specific storage duration. These findings are expected to help establish maintenance cycles for military equipment that use a refractive index matching gel, enhancing their reliability in military applications.

Controlling the emulsion stability of cosmetics through shear mixing process

Kwang-Mo Kim,오희묵,이준협 한국유변학회 2020 Korea-Australia rheology journal Vol.32 No.4

The manipulation of emulsion stability for kinetically sustainable cosmetic emulsions is an important technology in cosmetic industry, however the relationship between emulsifying process and long-term emulsion stability has not been elucidated. Herein, the effect of shear mixing process on the stability of oil-in-water cosmetic emulsions is investigated by varying the shear mixing rate, emulsification time, and water phase temperature. The analysis on droplet size distribution and shear viscosity revealed that the strong viscous forces at optimal shear mixing rate of 4000 rpm afforded the fine and uniform droplets for cosmetic emulsions, leading to the improvement of long-term emulsion stability. Moreover, since the prolonged shear mixing induced the destabilization of emulsion droplets through droplet coalescence, optimal shear mixing time of 3 min could improve the kinetic stability of cosmetic emulsions. The dependence of long-term emulsion stability on emulsification temperature was relatively low. The theoretical analysis using the Derjaguin-Landau-Verwey-Overbeek theory demonstrated that the shear mixing rate played a major role in sustaining fine and uniform cosmetic emulsions with long-term stability. The present study can greatly contribute to the fabrication of functional cosmetic emulsions with long-term stability by controlling the shear mixing parameters in simple emulsification process.

군 초급장교의 직업안정성 및 복무활성화에 관한 연구

박동순 대한민국재향군인회 안보전략연구원 2024 재향군인회 안보전략연구 Vol.11 No.-

한국은 인구절벽과 병 복무기간 단축 등으로 초급간부 모집에 비상이 걸렸다. 특히 비육사 출신 장교들은 장기복무선발에 대한 부담 등 직업안정성의 미 보장으로 인해 지원율이 급감하고 중도에 포기 인원도 늘고 있다. 육군3사관학교는 1968년 단기사관학교로 출발했으나, 1994년부터 생도 3, 4학년과정을 교육 후 임관시키는 ‘편입학사관학교’로 변신했다. 이 연구는 3사 출신의 직업 안정성 보장을 위한 법령 및 제도개선에 관한 것으로 우수자원의 장기적 확보에 기여할 목적으로 출발했다. 먼저 군의 복무환경 변화를 인식하고 3사 관련 법령의 형평성문제와 졸업자의 장기복무 실태를 분석했다. 이를 통해 관련 법령의 일부를 개정해야할 소요를 제시했다. 부가적으로 장기복무선발 등 인력운영시스템의 개선 등 관련 인사운영 정책의 개선을 도출하였다. 연구를 통해「육군3사관학교설치법」과「군인사법」의 장기복무선발 관련 조항에 대한 개정 필요성과 당위성을 중심으로 정책적 개선방향을 도출했다. 이를 바탕으로 사관학교 출신 초급장교의 직업안정성을 보장하고 출신 간 형평성을 유지하기 위해 장기복무선발 법령과 제도를 개선함으로써 육군3사관학교 특성을 고양하고 강군육성에 기여해야 할 것이다. Korea Army Academy at Yeongcheon(KAAY) started as a short-term military academy in 1968, but since 1994, it has been a ‘transfer academy’ that commissions 3rd and 4th year cadets after training. In Korea, there is an emergency in recruiting entry-level executives due to the population cliff and shortened military service period. In particular, the application rate for cadets among officers from the KAAY is rapidly decreasing due to the burden of being selected for long-term service and the lack of job security, and the number of officers giving up after commissioning is also increasing. This study is about improving laws and systems to ensure job stability for employees from the KAAY, and was started with the purpose of contributing to the long-term securing of excellent resources. First, we recognized changes in the military service environment and analyzed equity issues in laws related to the KAAY and the long-term service status of graduates. Through this, the need to revise some of the relevant laws was presented. Additionally, improvements were made to related personnel management policies, including improvements in the human resources management system, such as long-term service selection. Through research, policy improvement directions were derived focusing on the necessity and justification for revision of the provisions related to long-term service selection in the 「Act on Establishment of the Korea Army Academy at Yeongcheon(KAAY)」 and the 「Military Personnel Management Act」. As a result of the study, in order to ensure job stability, long-term service selection laws and systems must be improved and the characteristics of the KAAY must be enhanced to contribute to the development of a strong military.

시설유형별 요양보호사의 직무만족도와 근무안정성과의 관계에서 자기효능감의 조절효과

유연서 동방문화대학원대학교 문화예술콘텐츠연구소 2023 문화와예술연구 Vol.23 No.-

본 연구의 목적은 노인장기요양보험법 관련 시설에 종사하는 요양보호사의 직무만족도와 자기효능감, 그리고 근무안정성과의 관계를 고찰하는 것이며 특히 관련 시설 중 노인요양시설과 재가노인복지시설을 대표하는 주야간보호센터를 비교 분석하고자 한다. 노인장기요양보험법 관련 시설 요양보호사의 근무안정성을 제고하기 위하여 요양보호사의 전문성 향상 및 고용에 대한 안정성을 확보하기 위한 방안을 마련할 수 있는 구체적인 운영전략을 제시하고자 한다. 이를 위해 노인장기요양보험 관련 시설별 요양보호사의 직무만족도와 근무안정성과의 관계에서 자기효능감의 조절효과를 분석하기 위해 서울시 소재 노인요양시설과 재가노인복지시설에서 근무하는 요양보호사 810명을 대상으로 자기 기입식 설문조사를 실시하였다. 수집된 자료를 기술통계, 상관관계분석 및 위계적 회귀분석을 실시한 결과 다음과 같은 결론이 도출되었다. 첫째, 노인요양시설의 경우 학력, 직무만족도가 근무안정성에 영향을 미친 것으로 나타났으므로, 학력별 근무안정성을 높이기 위한 노력과 직무만족도가 낮은 요양보호사들을 대상으로 근무안정성을 향상시키기 위한 개입 노력이 필요하다. 둘째, 재가노인복지시설과 노인요양시설 모두 직무만족도는 근무안정성에 정적인 영향을 미친 것으로 나타났으므로, 요양보호사의 근무안정성을 높이기 위해서는 직무만족도를 향상시켜야 한다. 셋째, 시설 유형별 요양보호사의 직무만족도와 근무안정성과의 관계에서 자기효능감의 조절효과가 나타났으므로 자기효능감을 향상시키기 위한 프로그램이 필요하다. 본 연구의 결론을 토대로 노인장기요양 관련 시설별 요양보호사들의 근무안정성을 높이기 위해 직무만족도 수준의 향상과 자기효능감을 증진하기 위한 실천적방안을 제언하였다. This study examines the relationship between job satisfaction, self-efficacy, and work stability of nursing care workers in facilities related to the Long-Term Care Insurance Act for the Elderly, and in particular, compares and analyzes day and night care centers representing elderly care facilities and home-based elderly welfare facilities among related facilities. In order to ease the work stability of nursing care workers in facilities related to the Long-Term Care Insurance Act for the Elderly, we would like to present specific operational strategies to come up with measures to improve the professionalism of nursing care workers and secure stability in employment. This study conducted a self-written survey of 810 nursing care workers working at senior care facilities and home care welfare facilities in Seoul to analyze the moderating effect of self-efficacy on the relationship between job satisfaction and work stability of nursing care workers in each facility related to long-term care insurance for the elderly.Descriptive statistics, correlation analysis, and hierarchical regression analysis were conducted on the collected data, and the following conclusions were drawn. First, in the case of elderly care facilities, academic background and job satisfaction were found to have affected work stability, so efforts to increase work stability by education and intervention efforts to improve work stability for nursing care workers with low job satisfaction are needed.Second, job satisfaction was found to have a positive effect on work stability in both home-based welfare facilities and elderly care facilities, so job satisfaction should be improved to increase work stability of nursing care workers. Third, since there was a moderating effect of self-efficacy in the relationship between job satisfaction and work stability of nursing care workers by facility type, a program to improve self-efficacy is needed. Based on the conclusion of this study, it was suggested that programs to improve the level of job satisfaction and self-efficacy are needed to increase the work stability of nursing care workers in each facility related to long-term care for the elderly.

Long-Term Shelf Lifetime of Polymer:Nonfullerene Solar Cells Stored under Dark and Indoor Light Environment

Sooyong Lee,Hwajeong Kim,Youngkyoo Kim 한국태양광발전학회 2020 Current Photovoltaic Research Vol.8 No.4

Here we report the long-term stability of polymer:nonfullerene solar cells which were stored under dark and indoor light condition. The polymer:nonfullerene solar cells were fabricated using bulk heterojunction (BHJ) layers of poly[(2,6-(4,8-bis(5-(2-ethylhexyl) thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl –5′,7-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c′]dithiophene-4,8-dione))] (PBDB-T) and 3,9-bis(6-methyl-2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene (IT-M). To investigate their long-term stability, the PBDB-T:IT-M solar cells were stored in an argon-filled glove box. One set of the fabricated solar cells was completely covered with an aluminum foil to prevent any effect of light, whereas another set was exposed to indoor light. The solar cells were subjected to a regular performance measurement for 40 weeks. Results revealed that the PBDB-T:IT-M solar cells underwent a gradual decay in performance irrespective of the storage condition. However, the PBDB-T:IT-M solar cells stored under indoor light condition exhibited relatively lower power conversion efficiency (PCE) than those stored under the dark. The inferior stability of the solar cells under indoor light was explained by the noticeably changed optical absorption spectra and dark spot generation, indicative of degradations in the BHJ layers.

Long-term Stability of Conducting Polymers in Iodine/iodide Electrolytes: Beyond Conventional Platinum Catalysts

Kim, Sung June,Kwon, Jeong,Nam, Jae Keun,Kim, Wanjung,Park, Jong Hyeok Pergamon Press 2017 Electrochimica Acta Vol. No.

<P><B>Abstract</B></P> <P>One of the primary obstacles to the commercialization of dye-sensitized solar cells (DSSCs) is the improvement of their long-term stability. Here, we report greatly improved long-term stability of DSSCs, which have PEDOT:FTS polymer as a counter electrode. DSSCs with this PEDOT:FTS film demonstrate slightly lower power conversion efficiency of 8.1% under standard conditions (AM 1.5G, 100mWcm<SUP>−2</SUP>) compared to the ∼9.1% efficiency of Pt, using an electrolyte with iodine/iodide, which is the most popular redox shuttle. However, we demonstrate that this conducting polymer counter electrode facilitates the fabrication of solar cells with greatly improved long-term stability compared to Pt-based ones after exposure to electrolyte soaking conditions. Various electrochemical analyses were performed to evaluate the enhanced durability of PEDOT:FTS polymer in the highly corrosive iodine/iodide electrolyte under a continuous redox reaction condition.</P>

Stability of non-biofouling alginate/ZrIV coatings on Ti/TiO2 substrates

정연우,김인호,강성민 한국고분자학회 2024 Macromolecular Research Vol.32 No.1

Surface modification with alginate (Alg) has attracted significant attention because of its potential applications in nonbiofouling surface preparation, tissue engineering, and drug delivery. Much effort has been made to develop facile methods for preparing stable Alg coatings, including metal ion-mediated cross-link formation between polydopamine-coated solid surfaces and Alg. Although this approach has yielded Alg coatings that strongly inhibit platelet adhesion and fibrinogen adsorption on solid surfaces, their long-term stability, which is a prerequisite for practical applications, remains unknown. This study evaluated the long-term stability of Alg coatings under physiological conditions. The Alg coatings were incubated in phosphate-buffered saline at 37.5 °C for up to four weeks and subsequently analyzed for non-biofouling properties. The analysis revealed that the anti-protein adsorption and antiplatelet adhesion properties of the Alg coating were maintained at 80 and 90%, respectively, after four weeks of incubation. This study provides valuable insights into the long-term stability of Alg coatings and their potential for practical applications, addressing an overlooked crucial aspect. The findings contribute to advancements in tissue engineering, drug delivery systems, and other biomedical applications by enhancing our understanding of Alg coatings' durability and guiding the design of robust non-biofouling materials.

염료감응 태양전지 모듈의 장기안정성 향상을 위한 실링기술 연구

이광수(Kwangsoo Lee),고민재(Min Jae Ko) 한국태양광발전학회 2016 Current Photovoltaic Research Vol.4 No.4

Long-term stability of dye-sensitized solar cell (DSSC) module is critical for the commercialization. We investigated the effect of sealing technology on the long-term stability of the 10 ㎝ × 11 ㎝ sized DSSC modules. We applied the concept of secondary sealing to the module and then performed several stability tests such as humidity cycle, 1 sun light soaking and outdoor stability tests. The enhanced stability was confirmed for the DSSC module employing optimized sealing materials and architectures.