• Title/Summary/Keyword: primary stress

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Welding Residual Stress Distributions for Dissimilar Metal Nozzle Butt Welds in Pressurized Water Reactors (가압경수로 노즐 맞대기 이종금속용접부의 용접잔류응력 예측)

  • Kim, Ji-Soo;Kim, Ju-Hee;Bae, Hong-Yeol;Oh, Chang-Young;Kim, Yun-Jae;Lee, Kyung-Soo;Song, Tae-Kwang
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.2
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    • pp.137-148
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    • 2012
  • In pressurized water nuclear reactors, dissimilar metal welds are susceptible to primary water stress corrosion cracking. To access this problem, accurate estimation of welding residual stresses is important. This paper provides general welding residual stress profiles in dissimilar metal nozzle butt welds using finite element analysis. By introducing a simplified shape for dissimilar metal nozzle butt welds, changes in the welding residual stress distribution can be seen using a geometry variable. Based on the results, a welding residual stress profile for dissimilar metal nozzle butt welds is proposed that modifies the existing welding residual stress profile for austenitic pipe butt welds.

Interleaved ZVS Resonant Converter with a Parallel-Series Connection

  • Lin, Bor-Ren;Shen, Sin-Jhih
    • Journal of Power Electronics
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    • v.12 no.4
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    • pp.528-537
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    • 2012
  • This paper presents an interleaved resonant converter with a parallel-series transformer connection in order to achieve ripple current reduction at the output capacitor, zero voltage turn-on for the active switches, zero current turn-off for the rectifier diodes, less voltage stress on the rectifier diodes, and less current stress on the transformer primary windings. The primary windings of the two transformers are connected in parallel in order to share the input current and to reduce the root-mean-square (rms) current on the primary windings. The secondary windings of the two transformers are connected in series in order to ensure that the transformer primary currents are balanced. A full-wave diode rectifier is used at the output side to clamp the voltage stress of the rectifier diode at the output voltage. Two circuit modules are operated with the interleaved PWM scheme so that the input and output ripple currents are reduced. Based on the resonant behavior, all of the active switches are turned on under zero voltage switching (ZVS), and the rectifier diodes are turned off under zero current switching (ZCS) if the operating switching frequency is less than the series resonant frequency. Finally, experiments with a 1kW prototype are described to verify the effectiveness of the proposed converter.

Expression of HSP70 mRNA and Protein based on the Thermal Stress in the Primary Hepatocyte Culture of Walleye Pollock (Gadus chalcogrammus) (명태(Gadus chalcogrammus)의 일차 간세포 배양에서 온도 스트레스에 따른 HSP70 mRNA와 단백질 발현)

  • Kim, So-Sun;Lee, Chang-Ju;Park, Jang-Su
    • Journal of Environmental Science International
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    • v.29 no.6
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    • pp.633-641
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    • 2020
  • Water temperature is one of the most important factors of fish survival, affecting the habitat, migration route, development, and reproduction. This experiment studied the induction level of heat shock protein (HSP70) mRNA and protein in a walleye pollock (Gadus chalcogrammus) primary hepatocyte culture based on different temperatures. Hepatocytes were attached at 7.5℃ for 24 hours. Hsp70 induction levels were then measured for 48 hours at 5, 8, 11, 14, and 17℃. The induction level was lowest at 5℃ and generally increased with temperature until 14℃. The induction level was reduced at 17℃, indicating that 14℃ is the highest tolerable temperature for hepatocytes. These data indicate that primary hepatocyte cell culture is under no stress at 5 and 8℃. Temperatures greater than 11℃ induce stress, showing similar induction patterns in both mRNA and protein in hepatocytes. The results suggest that 14℃ is the maximum internal defense temperature of walleye pollock survival.

Optimization Design on the Sealing Surface Profiles of Contacting Seal Units (접촉식 시일장치의 밀봉 접촉면 형상에 대한 최적화 설계연구)

  • Kim, Chung-Kyun
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.20 no.6
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    • pp.761-766
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    • 2011
  • In this study, the optimized design profiles between a seal ring and a seal seat of contacting seal units has been proposed based on the FEM computed results. The maximum temperatures, the thermal distortions in axial and radial directions, and maximum contact normal stresses between a seal ring and a seal seat have been analyzed for various contact sealing profiles. The FEM computed results present that the contact area between seal rings and seal seats is very important for a good tribological performance such as low friction heating, low wear, high contact normal stress in a primary sealing components. The seal surface model III in which has a small sealing contact area shows low dilatation of primary sealing components, and high contact stress between a seal ring and a seal seat. This model with small contact surface of a seal ring produces high friction heating and contact stress. But the model III produces very small deformations of contacting sealing surface because of high convection heat transfer by cooling water circulation around the seal ring surface. Thus, the analysis results recommend a short width of a primary sealing unit rather than a big width of contact surfaces of contacting seal units for reducing a leakage and axial deformation of primary seal components.

Thermal creep behavior of CZ cladding under biaxial stress state

  • Jin, Xin;Lin, Yuyu;Zhang, Libin
    • Nuclear Engineering and Technology
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    • v.52 no.12
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    • pp.2901-2909
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    • 2020
  • Thermal creep is a key property of zircaloy cladding. CZ developed by CGN is a new zircaloy used as PWR fuel cladding. This research is devoted to investigating the thermal creep behavior of CZ and build the thermal creep model of CZ. Twenty internal pressure creep tests were conducted, and the ranges of temperature and Tresca stress were 320-430 ℃ and 70-300 MPa, respectively. Real-time creep data were analyzed by separating primary creep and steady-state creep. Based on Soderberg model and creep test data, CZ thermal creep model is derived. As a whole, the mean value and the standard deviation of P/M of CZ saturated primary creep strain are very close to these from steady-state creep rate, however, the predictive effect of primary creep is less satisfactory. Four conditions, where there exists large deviation between predicted values and test data, are 320 ℃ and 300 MPa, 350 ℃ and 190 MPa, 380 ℃ and 160 MPa, 380 ℃ and 190 MPa, respectively. As primary creep was much smaller than steady-state creep in long-time operation, the thermal creep model built can be applied to predict the thermal creep behavior of CZ cladding.

Insomnia in Medical Illnesses:The Secondary Insomnia (내과적 질환에 동반된 불면증:이차성 불면증)

  • Lim, Se-Won;Kim, Leen
    • Sleep Medicine and Psychophysiology
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    • v.12 no.1
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    • pp.11-16
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    • 2005
  • Sleep can be easily disrupted by variety of conditions. Most of medical illnesses could be a primary condition causing secondary insomnia. The common underlying mechanism of secondary insomnia is presumed to be stress effects on sleep. The assessment and treatment of secondary insomnia are often complicated. Establishing an causal inference between primary condition and insomnia is the key to assessment. However, it can be difficult even for experienced clinicians due to diagnostic ambiguity of secondary insomnia. Therefore, through medical evaluation and integrative understanding of primary condition is essential to manage secondary insomnia properly. Although treatment have been usually focused on the primary medical illnesses per se, nonpharmacologic interventions, such as sleep hygiene, might be effective in many cases.

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Mechanical Behavior and Microstructure Evolution during Semi-Solid Squeeze Cast Processing of Ignition-Proof Mg-Zn-Ca-Zr Alloy

  • Chang, Si-Young;Choi, Jung-Chul
    • Journal of Korea Foundry Society
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    • v.17 no.5
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    • pp.502-509
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    • 1997
  • The mechanical behavior and microstructural evolution in the ignition-proof Mg-Zn-Ca-Zr alloy produced by the semisolid squeeze casting are clarified and the mechanical properties are also compared with those of squeeze cast Mg-Zn-Ca-Zr alloy. The tensile strength and elongation increase slightly as the solid fraction depending on temperature decreases, while the 0.2% proof stress decreases. The size of primary crystal increases with increasing holding time. The tensile strength and 0.2% proof stress of the semi-solid squeeze cast Mg-Zn-Ca-Zr alloy decrease as the size of primary crystal increases, indicating the dependence of strength on the size of primary crystal. The elongation of the semi-solid squeeze cast Mg-Zn-Ca-Zr alloy is two times as large as the squeeze cast Mg-Zn-Ca-Zr alloy and the tensile strength is unchanged despite the growth of primary crystal, resulting from the refining of the melted ${\alpha}Mg$ phase and the brittle eutectic compound as well as the reduction of solidification shrinkage and porosities.

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A Case of Soyangin Daylong Generalized Primary Hyperhidrosis (종일 지속되는 소양인 원발성 전신 다한증의 치험 1례)

  • Soo Yeon Chae;Seong-Sik Park
    • Journal of Sasang Constitutional Medicine
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    • v.35 no.4
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    • pp.65-71
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    • 2023
  • Objectives This case study aimed to report the improvement of stress-induced generalized primary hyperhidrosis of Soyangin patient. Methods Soyangin patient suffering from daylong generalized primary hyperhidrosis was treated with acupuncture, psychological counseling, and herbal medicine. The severity of hyperhidrosis was measured using Visual Analog Scale (VAS). Results & Conclusions After treatment with Tae-Geuk acupuncture, Dojeokganggi-tang, and psychological counseling, the VAS score of hyperhidrosis was reduced from 10 to 2 during three days of admission. Herbal medicine was prescribed for 30 more days after discharge. The relieved state was maintained when monitored after two months. This case report proposes the potential of Sasang constitutional medicine for stress-induced generalized primary hyperhidrosis.

Mechanical Properties and Modeling of Amorphous Metallic Fiber-Reinforced Concrete in Compression

  • Dinh, Ngoc-Hieu;Choi, Kyoung-Kyu;Kim, Hee-Seung
    • International Journal of Concrete Structures and Materials
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    • v.10 no.2
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    • pp.221-236
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    • 2016
  • The aim of this paper is to investigate the compressive behavior and characteristics of amorphous metallic fiber-reinforced concrete (AMFRC). Compressive tests were carried out for two primary parameters: fiber volume fractions ($V_f$) of 0, 0.3, 0.6 and 0.8 %; and design compressive strengths of 27, 35, and 50 MPa at the age of 28 days. Test results indicated that the addition of amorphous metallic fibers in concrete mixture enhances the toughness, strain corresponding to peak stress, and Poisson's ratio at high stress level, while the compressive strength at the 28-th day is less affected and the modulus of elasticity is reduced. Based on the experimental results, prediction equations were proposed for the modulus of elasticity and strain at peak stress as functions of fiber volume fraction and concrete compressive strength. In addition, an analytical model representing the entire stress-strain relationship of AMFRC in compression was proposed and validated with test results for each concrete mix. The comparison showed that the proposed modeling approach can properly simulate the entire stress-strain relationship of AMFRC as well as the primary mechanical properties in compression including the modulus of elasticity and strain at peak stress.

Prediction of Welding Residual Stress of Dissimilar Metal Weld of Nozzle using Finite Element Analyses (유한요소해석을 이용한 노즐 이종금속용접부의 용접잔류응력 예측)

  • Huh, Nam-Su;Kim, Jong-Wook;Choi, Suhn;Kim, Tae-Wan
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.83-84
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    • 2008
  • The primary water stress corrosion cracking (PWSCC) of dissimilar metal weld based on Alloy 82/182 is one of major issues in material degradation of nuclear components. It is well known that the crack initiation and growth due to PWSCC is influenced by material's susceptibility to PWSCC and distribution of welding residual stress. Therefore, modeling the welding residual stress is of interest in understanding crack formation and growth in dissimilar metal weld. Currently in Korea, a numerical round robin study is undertaken to provide guidance on the welding residual stress analysis of dissimilar metal weld. As a part of this effort, the present paper investigates distribution of welding resisual stress of a ferritic low alloy steel nozzle with dissimilar metal weld using Alloy 82/182. Two-dimensional thermo-mechanical finite element analyses are carried out to simulate multi-pass welding process on the basis of the detailed design and fabrication data. The present results are compared with those from other participants, and more works incorporating physical measurements are going to be performed to quantify the uncertainties relating to modelling assumptions.

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