• Title/Summary/Keyword: Burst Type

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Structural Integrity Evaluation of SG Tube with Surface Wear-type Defects (표면 마모결함을 고려한 증기발생기 세관의 구조건전성 평가)

  • Kim, Jong-Min;Huh, Nam-Su;Chang, Yoon-Suk;Hwang, Seong-Sik;Kim, Joung-Soo;Kim, Young-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.12 s.255
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    • pp.1618-1625
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    • 2006
  • During the last two decades, several guidelines have been developed and used for assessing the integrity of a defective steam generator (SG) tube that is generally caused by stress corrosion cracking or wall-thinning phenomenon. However, as some of SG tubes are also failed due to fretting and so on, alternative failure estimation schemes are required for relevant defects. In this paper, parametric three-dimensional finite element (FE) analyses are carried out under internal pressure condition to simulate the failure behavior of SG tubes with different defect configurations; elliptical wear, tapered and flat wear type defects. Maximum pressures based on material strengths are obtained from more than a hundred FE results to predict the failure of SG tube. After investigating the effect of key parameters such as defect depth, defect length and wrap angle, simplified failure estimation equations are proposed in relation to the equivalent stress at the deepest point in wear region. Comparison of failure pressures predicted by the proposed estimation scheme with corresponding burst test data showed a good agreement.

Health Monitoring of a Composite Actuator with a PZT Ceramic during Electromechanical Fatigue Loading

  • Woo, Sung-Choong;Goo, Nam-Seo
    • Journal of the Korean Society for Nondestructive Testing
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    • v.27 no.6
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    • pp.541-549
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    • 2007
  • This work describes an investigation into the feasibility of using an acoustic emission (AE) technique to evaluate the integrity of a composite actuator with a PZT ceramic under electromechanical cyclic loading. AE characteristics have been analyzed in terms of the behavior of the AE count rate and signal waveform in association with the performance degradation of the composite actuator during the cyclic tests. The results showed that the fatigue cracking of the composite actuator with a PZT ceramic occurred only in the PZT ceramic layer, and that the performance degradation caused by the fatigue damage varied immensely depending on the existence of a protecting composite bottom layer. We confirmed the correlations between the fatigue damage mechanisms and AE signal types for the actuators that exhibited multiple modes of fatigue damage; transgranular micro damage, intergranular fatigue cracking, and breakdown by a short circuiting were related to a burst type signal showing a shortly rising and slowly decaying waveform with a comparably low voltage, a continuous type signal showing a gradual rising and slowly decaying waveform with a very high voltage and a burst and continuous type signal with a high voltage, respectively. Results from the present work showed that the evolution of fatigue damage in the composite actuator with a PZT ceramic can be nondestructively identified via in situ AE monitoring and microscopic observations.

Development of Subminiature Type 3 Composite Pressure Vessel for Cooling Unit in Electric Appliances (전자제품 쿨링 유닛용 초소형 타입 복합재 압력용기 개발)

  • Cho, Sung-Min;Lee, Seung-kuk;Moon, Jong-sam;Lyu, Sung-ki
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.17 no.6
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    • pp.151-157
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    • 2018
  • In this study, we have developed a composite pressure vessel that is compact and can store refrigerant at high pressure to increase the refrigerant volume. The composite pressure vessel is made of aluminum-based duralumin, which has high rigidity and excellent elongation in the inner liner, considering the characteristics of products in the aerospace and defense industry, where the safety of the applied product is considered as a priority. High strength carbon fiber was applied to the outside. In order to evaluate the performance of the developed product, burst test and cycling test were carried out. In burst test, an excellent safety margin equivalent to 2.7 times the operating pressure was obtained. In cycling test, a stable failure mode in which 'pre-burst leak' occurs is proved and the soundness of the product is proved.

TRANSIT OF THE INTERPLANETARY SHOCKS ASSOCIATED WITH TYPE II RADIO BURSTS WITHIN 1AU (Type II 전파폭발이 관측된 행성간 충격파의 1AU 내에서의 전파 과정)

  • Oh, Su-Yeon;Yi, Yu;Kim, Yong-Ha
    • Journal of Astronomy and Space Sciences
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    • v.24 no.3
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    • pp.219-226
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    • 2007
  • Among the interplanetary shock (IP shock)s observed by ACE spacecraft at 1AU during 1997 to 2000, we have selected 31 IP shocks which had triggered the interplanetary type II radio bursts detected by the WIND spacecraft while those shocks were leaving the Sun. We compared the observed IP shock propagation speeds and the IP shock transit speeds estimated by time difference between the interplanetary type II radio burst detection and the IP shock observation. Then, we found that the mean acceleration of the IP shocks between the Sun and the Earth is about $-1.02m/sec^2$, which means the deceleration contrary to the positive acceleration predicted by Parker solar wind model. It is also verified that the acceleration of the IP shock does not show any linear correlation with the shock propagation speed and the Mach number of the IP shock.

Design Procedure of the Inverter for LCD Backlight using Piezoelectric Transformer (압전 변압기를 이용한 LCD 백라이트 구동용 인버터 설계 절차)

  • Kweon Gie-Hyoun;Cho Sung-Koo;Lim Young-Cheol;Yang Seung-Hak
    • The Transactions of the Korean Institute of Power Electronics
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    • v.9 no.6
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    • pp.577-583
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    • 2004
  • Optimal parameters were selected to design an inverter circuit that drives a cold cathode fluorescent lamp for LCD backlight using a piezoelectric transformer and it was verified by an experiment. In this paper, the applied inverter topologies are a push-pull type and a half-bridge type, and the dimming control methods of these drive system were used a analog control method and a burst control method each other. When change a control voltage from 2.5V to 4.5V in the analog control method, the brightness 0-100% was seen in current 1-6 mA. And, the input/output efficiency were obtained 90.3%. Also, the control performance of 1-6 mA was seen in duty ratio 5-50% in the burst control method, and the input/output efficiency of the designed inverter got 82.1%.

A Solar Stationary Type IV Radio Burst and Its Radiation Mechanism

  • Liu, Hongyu;Chen, Yao;Cho, Kyungsuk;Feng, Shiwei;Vasanth, Veluchamy;Koval, Artem;Du, Guohui;Wu, Zhao;Li, Chuanyang
    • The Bulletin of The Korean Astronomical Society
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    • v.43 no.1
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    • pp.52.2-53
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    • 2018
  • A stationary Type IV (IVs) radio burst was observed on September 24, 2011. Observations from the Nançay RadioHeliograph (NRH) show that the brightness temperature (TB ) of this burst is extremely high, over 10^11K at 150 MHz and over 10^8K in general. The degree of circular polarization (q ) is between -60%~-100%, which means that it is highly left-handed circularly polarized. The flux-frequency spectrum follows a power-law distribution, and the spectral index is considered to be roughly -3~-4 throughout the IVs. Radio sources of this event are located in the wake of the coronal mass ejection and are spatially dispersed. They line up to present a formation in which lower-frequency sources are higher. Based on these observations, it is suggested that the IVs was generated through electron cyclotron maser emission.

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Adaptive Usage Parameter Control Mechanism using a Variable Token Pool in ATM Networks (ATM망에서 가변 토큰풀을 이용한 적응적 사용 파라메터 제어 메카니즘)

  • Koo, Ja-Gwang;Lee, Hwan-Chung;Kim, Chong-Gun
    • The Transactions of the Korea Information Processing Society
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    • v.4 no.9
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    • pp.2366-2377
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    • 1997
  • An Adaptive Usage Parameter Control(UPC) mechanism using a Variable Token Pool(VTP) which is kind of preventive traffic control in the Asynchronous Transfer Mode(ATM) networks is described. The VTP mechanism can monitor violations of the average bit rate and burst duration as well as peak bit rate for the ON-OFF type traffic. The VTP can vary the token pool size by monitoring burst duration and silence duration for a long term. It also improves the sensitivity against the violation of burst duration and average bit rate and enables to response for the violating traffic situation quickly. The variable token pool size is varied in step size by every burst duration and silence duration. Two important parameters for controlling token pool size are Down_size and Up_size. We compare the performance of LB and JW mechanism with the proposed VTP mechanism by computer simulations. We have known that the proposed method is more effective than the previous mechanisms. It is shown that the cell loss rate of the VTP quite depends on the value of Down_size and Up_size. The two parameters should be decided as a propr value according to traffic situations.

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Up-stream Channel Performance of Ethernet PON System Using $2{\times}32$ Splitter (전광섬유형 $2{\times}32$ 스프리터 제작과 이를 이용한 Ethernet PON 시스템의 상향통신채널 성능평가)

  • Jang, Jin-Hyeon;Kim, Jun-Hwan;Shin, Dong-Ho
    • Journal of The Institute of Information and Telecommunication Facilities Engineering
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    • v.4 no.2
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    • pp.29-36
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    • 2005
  • All-optical fiber-type $2{\times}32$ splitters for an Ethernet PON (passive optical network) were fabricated by using a FBT (fiber biconical tapered) process and the performance of the splitters was tested in upstream transmission of the EPON system. The $2{\times}32$ splitters was obtained by cascading $1{\times}4$ splitters fabricated by a conventional FBT process and showed -18 dB of insertion loss with 1.5 dB uniformity of output power at each channel and -0.1 dB of polarization dependent loss. The insertion loss variation was below 0.1 dB at the temperature range of $-40^{\circ}C\;to\;80^{\circ}C$. For upstream channel transmission test in the EPON system were a Zig board and a burst mode receiver. Zenko-made optical module was used for the burst mode receiver by adding functions of serializer/deserializer and clock data recovery, a Virtex II pro20 chipset and Vitesse VSC7123 were used in the Zig board for characterizing the burst mode and in the clock data recovery chipset, respectively. Startup acquisition lock time and data acquisition lock time were measured to be 670ns and 400ns, respectively, in the upstream channel transmission of the EPON system adapting the $2{\times}32$ splitter fabricated in this work.

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Preparation and Evaluation of Bupivacaine Microspheres by a Solvent Evaporation Method (용매증발법에 의한 부피바카인 microsphere의 제조 및 평가)

  • Kwak, Son-Hyok;Hwang, Sung-Joo;Lee, Byung-Chul
    • YAKHAK HOEJI
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    • v.44 no.6
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    • pp.511-520
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    • 2000
  • Various bupivacaine-loaded microspheres were prepared from poly (d,l-lactide) (PLA) or poly (d,l-lactic-co-glycolide) (PLGA) by a solvent evaporation method for the sustained release of drug. PLA and PLGA microspheres were prepared by w/o/w and w/o/o multiple emulsion solvent evaporation, respectively. The effects of process conditions such as emulsification speed, emulsifier type, emulsifier concentration and internal/external phase ratio on the characteristics of microspheres were investigated. The prepared microspheres were characterized for their drug loading, size distribution, surface morphology and release kinetics. Drug loading efficiency was higher in the microspheres prepared by w/o/o multiple emulsion than that by w/o/w multiple emulsion method, because the solubility of bupivacaine HCI was decreased in oil phase compared with water phase. The prepared microspheres had an average diameter between 1 and $2\;{\mu}M$ in all conditions of two methods. In morphology studies the PLA microspheres showed an irregular shape and smooth surface, but PLGA microspheres had a spherical shape and smooth surface. The release pattern of the drug from microspheres was evaluated on the basis of the burst effect and the extent of the release after 24h. The in vitro release of bupivacaine HCl from microspheres showed a large initial burst release and $60{\sim}80%$ release within one day in all conditions of two methods. The extents of the burst release against PLA and PLGA microspheres were $30{\sim}50%$ and $50{\sim}80%$ within 20min, respectively. This burst release seems to be due to the smaller size of microspheres and the solubility of drug in water.

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