• Title, Summary, Keyword: Super stability

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Teflon coating of fabric filters for enhancement of high temperature durability (섬유상 여과필터의 고온 내구성 향상을 위한 테프론 코팅 연구)

  • Kim, Eun-Joo;Park, Young-Koo
    • Journal of the Korean Applied Science and Technology
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    • v.28 no.2
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    • pp.232-239
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    • 2011
  • Fabric fibrous filter has been used in various industrial applications owing to the low cost and wide generality. However, the basic properties of fabric materials often limit the practical utilization including hot gas cleaning. This study attempts to find new coatings of porous fibrous filter media in order to overcome its insufficient thermal resistance and durability. Teflon was one of the plausible chemicals to supplement the vulnerability against frequent external thermal impacts. A foaming agent composed of Teflon and some organic additives was tentatively coated on the glass fiber mat. The present test Teflon foam coated filter was fount to be useful for hot gas cleaning, up to $250^{\circ}C$-$300^{\circ}C$. Close examination using XPS(X-ray Photoelectron Spectroscopy) and Contact angle proved the binding interactions between carbon and fluorine, which implies coating stability. The PTFE/Glass foam coated filter consisted of more than 95% (C-F)n bond, and showed super-hydrophobic with good-oleophobic characteristics. The contact angle of liquid droplets on the filter surface enabled to find the filter wet-ability against liquid water or oil.

Earthquake Response Analysis of an Offshore Wind Turbine Considering Effects of Geometric Nonlinearity of a Structure and Drag Force of Sea Water (기하 비선형과 항력 효과를 고려한 해상풍력발전기의 지진 응답해석)

  • Lee, Jin Ho;Bae, Kyung Tae;Jin, Byeong Moo;Kim, Jae Kwan
    • Journal of the Earthquake Engineering Society of Korea
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    • v.17 no.6
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    • pp.257-269
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    • 2013
  • In this study, the capability of an existing analysis method for the fluid-structure-soil interaction of an offshore wind turbine is expanded to account for the geometric nonlinearity and sea water drag force. The geometric stiffness is derived to take care of the large displacement due to the deformation of the tower structure and the rotation of the footing foundation utilizing linearized stability analysis theory. Linearizing the term in Morison's equation concerning the drag force, its effects are considered. The developed analysis method is applied to the earthquake response analysis of a 5 MW offshore wind turbine. Parameters which can influence dynamic behaviors of the system are identified and their significance are examined.

Evaluation of Glass-forming Ability in Ca-based Bulk Metallic Glass Systems (칼슘기 벌크 비정질 합금에서 비정질 형성능 평가)

  • Park, Eun-Soo;Kim, Do-Hyang
    • Journal of Korea Foundry Society
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    • v.29 no.4
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    • pp.181-186
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    • 2009
  • The interrelationship between new parameter ${\sigma}$ and maximum diameter $D_{max}$ is elaborated and discussed in comparison with four other glass forming ability (GFA) parameters, i.e. (1) super-cooled liquid region ${\Delta}T_x (=T_x - T_g)$, (2) reduced glass transition temperature $T_{rg} (=T_g/T_l)$, (3) K parameter $K (=[T_x-T_g]/[T_l -T_x])$, and (4) gamma parameter ${\gamma}(=[T_x]/[T_l+T_g])$ in Ca-based bulk metallic glass (BMG) systems. The ${\sigma}$ parameter, defined as ${\Delta}T^*{\times}P^'$, has a far better correlation with $D_{max}$ than the GFA parameters suggested so far, clearly indicating that the liquid phase stability and atomic size mismatch dominantly affect the GFA of Ca-based BMGs. Thus, it can be understood that the GFA of BMGs can be properly described by considering structural aspects for glass formation as well as thermodynamic and kinetic aspects for glass formation.

Characteristic of DLC Thin Film Fabricated by FVAS Method on Tungsten Carbide (초경합금에 FVAS로 코팅한 DLC 박막의 특성)

  • Cheon, Min-Woo;Park, Yong-Pil;Kim, Tae-Gon;Lee, Ho-Shik
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.24 no.10
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    • pp.812-816
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    • 2011
  • An optical lens is usually produced in the manner of high temperature compression molding with tungsten carbide alloy molding cores, it is necessary to develop and study technology for super-precision processing of molding cores and coating the core surface. As main methods used in surface improvement technologies using thin film, DLC present high hardness, chemical stability, and outstanding durability of abrasion to be extensively applied in various industrial fields. In this study, the effect of DLC coating of a thin film by means of the FVAS (filtered vacuum arc source) analyzed the characteristics of thin film. Surface roughness before and after DLC coating was measured and the result showed that the surface roughness was improved after coating as compared to before coating. In conclusion, it was observed that DLC coating of the ultra hard alloy core surface for molding had an effect on improving the surface roughness and shape of the core surface. It is considered that this will have an effect on improving abrasion resistance and the service life of the core surface.

A Study on Hybrid Control Unit Using a Smart Control (스마트 제어를 이용한 하이브리드 형 제어장치 연구)

  • Kim, Hee-Chul
    • The Journal of the Korea institute of electronic communication sciences
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    • v.11 no.11
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    • pp.1093-1100
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    • 2016
  • This study is to demonstrate the superiority and stability of the solar - wind power hybrid power generation system for street lamps using super capacitor EDLC(:Electric Double Layer Capacitor). It is aiming to apply the lighting device using LED light source as the load of solar-wind power hybrid power generation system for independent power source and to develop the street light system device with high output power generation system. Unlike conventional controllers, EDLC, which is used as an auxiliary device for storing the developed power in the battery, can guarantee the high output and long life of the battery.

Long-Term Projection of Demand for Reverse Mortgage Using the Bass Diffusion Model in Korea (Bass 확산모형을 활용한 국내 주택연금의 중·장기 수요예측)

  • Yang, Jin-Ah;Min, Daiki;Choi, Hyung-Suk
    • Journal of the Korean Operations Research and Management Science Society
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    • v.42 no.1
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    • pp.29-41
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    • 2017
  • Korea is expected to become a super-aged society by 2050. Given an aging population and the increasing pressure for the early retirement, a sufficient social safety net for elderly population becomes important. The Korean government introduced public reverse mortgage program in 2007, which is a product for aging seniors and the elderly, The number of reverse mortgage subscribers has also steadily grown. The demand continues to grow, but the reverse mortgage over a long period of time is a highly uncertain and risky product in the position of guarantee or lending institution. Thus, suitable demand prediction of the reverse mortgage subscribers is necessary for stable and sustainable operation. This study uses a Bass diffusion model to forecast the long-term demand for reverse mortgage and provides insight into reverse mortgage by forecasting demand for stability and substantiality of the loan product. We represent the projections of new subscribers on the basis of the data obtained from Korea Housing Finance Corporation. Results show that potential market size of Korean reverse mortgage reaches approximately 760,000-1,160,000 households by 2020. We validate the results by comparing the estimate of the cumulative number of subscribers with that found in literature.

A Study on Outage Probability Analysis of HVDC Converter Considering Spare Elements (HVDC 변환소의 여유요소(Spare)를 고려한 사고확률 분석에 관한 연구)

  • Oh, Ungjin;Choi, Jaeseok;Kim, Chan-Ki;Yoon, Yongbeum
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.67 no.11
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    • pp.1408-1414
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    • 2018
  • Recently, as a solution to the problem of maintaining system reliability, stability, and quality occurring worldwide, such as activation of smart grid and recognition of super grid and rapid grid interconnection of renewable energy sources HVDC(High Voltage Direct Current) will appear on the front of the electric power system. These concepts are also very important concepts in HVDC systems. When the HVDC system is linked to the existing power system, it is composed of AC/DC/AC conversion device, and these conversion devices are composed of many thyristors. These parts(Devices) are connected in a complicated manner, and they belong to the one with a higher failure rate. However, the problem of establishing the concept of failure rate of HVDC parts directly linked to economic efficiency and the understanding accompanying it are still insufficient. Therefore, in this paper, we establish the meaning of reliability in power system and try to develop a model to analyze and verify the failure rate data of HVDC based on this.

Control Performance Evaluation of Mid-Story Isolation System for Residence-Commerce Complex Building (주상 복합 구조물에 적용된 중간층 면진 시스템의 성능 검토)

  • Park, Kwang-Seob;Kim, Yun-Tae;Kim, Hyun-Su
    • Journal of Korean Association for Spatial Structures
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    • v.19 no.3
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    • pp.33-40
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    • 2019
  • A seismic isolation system is one of the most effective control devices used for mitigating the structural responses due to earthquake loads. This system is generally used as a type of base isolation system for low- and mid-rise building structures. If the base isolation technique is applied to high-rise buildings, a lot of problems may be induced such as the movement of isolation bearings during severe wind loads, the stability problem of bearings under large compression forces. Therefore, a mid-story isolation system was proposed for seismic protection of high-rise buildings. Residence-commerce complex buildings in Korea have vertical irregularity because shear wall type and frame type structures are vertically connected. This problem can be also solved by the mid-story isolation system. An effective analytical method using super elements and substructures was proposed in this study. This method was used to investigate control performance of mid-story isolation system for residence-commerce complex buildings subjected to seismic loads. Based on numerical analyses, it was shown that the mid-story isolation system can effectively reduce seismic responses of residence-commerce complex tall buildings.

Design of Asynchronous Non-Volatile Memory Module Using NAND Flash Memory and PSRAM (낸드 플래시 메모리와 PSRAM을 이용한 비동기용 불휘발성 메모리 모듈 설계)

  • Kim, Tae Hyun;Yang, Oh;Yeon, Jun Sang
    • Journal of the Semiconductor & Display Technology
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    • v.19 no.3
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    • pp.118-123
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    • 2020
  • In this paper, the design method of asynchronous nonvolatile memory module that can efficiently process and store large amounts of data without loss when the power turned off is proposed and implemented. PSRAM, which takes advantage of DRAM and SRAM, was used for data processing, and NAND flash memory was used for data storage and backup. The problem of a lot of signal interference due to the characteristics of memory devices was solved through PCB design using high-density integration technology. In addition, a boost circuit using the super capacitor of 0.47F was designed to supply sufficient power to the system during the time to back up data when the power is off. As a result, an asynchronous nonvolatile memory module was designed and implemented that guarantees reliability and stability and can semi-permanently store data for about 10 years. The proposed method solved the problem of frequent data loss in industrial sites and presented the possibility of commercialization by providing convenience to users and managers.

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Evaluation of Thermal Durability for Thermal Barrier Coatings with Gradient Coating Thickness (경사화 두께를 갖는 열차폐 코팅의 열적 내구성 평가)

  • Lee, Seoung Soo;Kim, Jun Seong;Jung, Yeon-Gil
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.21 no.8
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    • pp.248-255
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    • 2020
  • The effects of the coating thickness on the thermal durability and thermal stability of thermal barrier coatings (TBCs) with a gradient coating thickness were investigated using a flame thermal fatigue (FTF) test and thermal shock (TS) test. The bond and topcoats were deposited on the Ni-based super-alloy (GTD-111) using an air plasma spray (APS) method with Ni-Cr based MCrAlY feedstock powder and yttria-stabilized zirconia (YSZ), respectively. After the FTF test at 1100 ℃ for 1429 cycles, the bond coat was oxidized partially and the thermally grown oxide (TGO) layer was observed at the interface between the topcoat and bond coat. On the other hand, the interface microstructure of each part in the TBC specimen showed a good condition without cracking or delamination. As a result of the TS test at 1100 ℃, the TBC with gradient coating thickness was initially delaminated at a thin part of the coating layer after 37 cycles, and the TBC was delaminated by more than 50% after 98 cycles. The TBCs of the thin part showed more oxidation of the bond coat with the delamination of topcoat than the thick part. The thick part of the TBC thickness showed good thermal stability and oxidation resistance of the bond coat due to the increased thermal barrier effect.