• 제목/요약/키워드: Longitudinal conduction

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TIG-FSW 하이브리드 용접을 이용한 이종재 맞대기 용접부의 잔류응력 해석 (Analysis of Residual Stress on Dissimilar Butt Joint by TIG Assisted Hybrid Friction Stir Welding)

  • 방희선;노찬승;엠 에스 비조이;방한서;이윤기
    • Journal of Welding and Joining
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    • 제30권2호
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    • pp.47-53
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    • 2012
  • This paper aimed to study and understand the mechanical phenomena of thermal elasto-plastic behavior on the dissimilar butt joint (Al 6061-T6 and STS304) by TIG assisted Friction Stir Welding. Heat conduction and residual stress analysis is carried out using in-house solver. Two-dimensional results of the heat distribution and residual stresses in dissimilar joint for particular tool geometry and material properties are presented. The predicted stress along longitudinal direction in Al 6061-T6 and STS304 are approximately between 12-15% of their respective yield strengths. A comparison is made between experimentally measured and numerically predicted equivalent residual stress values.

Association between hearing loss and high-sensitivity C-reactive protein: the Kangbuk Samsung Cohort Study

  • Jihoon Kim;Yesung Lee;Eunhye Seo;Daehoon Kim;Jaehong Lee;Youshik Jeong;Seonghyun Kwon;Jinsook Jeong;Woncheol Lee
    • Annals of Occupational and Environmental Medicine
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    • 제35권
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    • pp.38.1-38.10
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    • 2023
  • Background: Hearing loss (HL) is linked to an elevated risk of cardiovascular diseases (CVDs). The pathogeneses of HL and CVD commonly involve inflammatory responses. Previous studies investigated elevated levels of inflammatory biomarkers in subjects with HL, however, their findings did not demonstrate statistical significance. In our cross-sectional and longitudinal study, we investigated the correlation between HL and increased high-sensitivity C-reactive protein (hsCRP) levels to determine how HL is associated with CVDs. Methods: We conducted a cross-sectional study with workers aged over 18 years who underwent health check-ups at our institution between 2012 and 2018 (n = 566,507), followed by conducting a longitudinal study of workers aged > 18 who underwent health checkups at least twice at our institution between 2012 and 2018 (n = 173,794). The definition of HL was as an average threshold of ≥ 20 dB in pure-tone air conduction at 0.5, 1.0, and 2.0 kHz in both ears. The incidence of increased hsCRP levels throughout the follow-up period was defined as a level exceeding 3 mg/L. Logistic regression and generalized estimating equations were performed to estimate the risk of increased hsCRP levels according to the occurrence of HL in groups stratified by age. Results: In the cross-sectional study, the multivariate-adjusted odds ratio (OR) was 1.17 (95% confidence interval [CI]: 1.02-1.34); the OR was 0.99 (95% CI: 0.80-1.22) in those under 40 and 1.28 (1.08-1.53) in those over 40. In the longitudinal study, the multivariable-adjusted OR was 1.05 (95% CI: 0.92-1.19); the OR was 1.10 (95% CI: 0.90-1.35) in those under 40 and 1.20 (1.01-1.43) in those over 40. Conclusions: This cross-sectional and longitudinal study identified an association between HL and increased hsCRP levels in workers aged over 40 years.

산화물 초전도선재의 상전도전파특성 (Normal-zone Propagation Properties in Oxide Superconductors)

  • 김석범;석산돈사;한경희
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1996년도 하계학술대회 논문집 A
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    • pp.41-43
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    • 1996
  • This paper describes on concerning electromagnetical and thermal behaviors during normal transition in Bi-2223/Ag superconducting multifilamentary tapes by conduction cooling. Some experiments were carried with operating temperature, 10-40K, and transport current as parameters in zero magnetic field. Sample tapes are transited normally with heater to intiate a quench. The voltage and temperature properties which accord to normal transition are measured by voltage taps and thermocouples attached to sample tapes, we also calculated longitudinal and transverse directions normal-zone propagation velocities from the voltage traces.

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2차원적으로 무질서화된 텅스텐 칼코겐화물의 열적특성에 관한 연구 (Thermal Property of 2D-Disordered Tungsten Chalcogenides)

  • 김종영;장경주;피재환;조광연;최순목;서원선;김경자
    • 한국세라믹학회지
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    • 제47권2호
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    • pp.132-135
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    • 2010
  • Thermal properties of layered metal chalcogenides such as $WT_2$ (T=S,Se) with two-dimensionally disordered structure were evaluated. Thermal conductivity shows a marked decrease after exfoliation and subsequent restacking because of random stacking of two-dimensional crystalline sheet, which circumvents thermal conduction pathways along longitudinal direction in anisotropic materials.

과도응답해석을 이용한 열교환기의 성능평가방법에 관한 연구 (Performance evaluation technique of a heat exchanger using a transient response analysis)

  • 박병규;홍택;박상희
    • 설비공학논문집
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    • 제11권1호
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    • pp.81-90
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    • 1999
  • The performance evaluation technique of a heat exchanger is described by using a transient response analysis for the determination of an average heat transfer coefficient. The model using a finite difference method can accommodate arbitrary inlet fluid temperature as well as longitudinal conduction. Temperature histories are obtained from the experiments at the inlet and outlet of test core. Heat transfer coefficient and friction factor of the plate array are obtained in short times using the data reduction program of transient response analysis in the single-blow method. The results agree very well with theoretical results. It is shown that the rms deviations are very small and the performance evaluation technique gives rapid and accurate results.

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Thermal and Electronic Properties of Exfoliated Metal Chalcogenides

  • Kim, Jong-Young;Choi, Soon-Mok;Seo, Won-Seon;Cho, Woo-Seok
    • Bulletin of the Korean Chemical Society
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    • 제31권11호
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    • pp.3225-3227
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    • 2010
  • The thermal conductivity of layered metal chalcogenides such as $MT_2$ (M = Mo, W; T = S, Se) shows a marked decrease after exfoliation and subsequent restacking process. Random stacking of two-dimensional crystalline sheets circumvents thermal conduction pathways along a longitudinal direction, which results in a reduction in thermal conductivity. $WS_2$ and $WSe_2$ compounds retain p-type conducting behavior after exfoliation and restacking with decreased electrical conductivity due to the change in carrier concentration. $MoSe_2$ compound exhibits metallic behavior < $130^{\circ}C$ with a small Seebeck coefficient, which results from metastable 1T-$MoSe_2$ structure of the restacked phase.

오프셋 스트립 휜을 가지는 리큐퍼레이터의 내부 형상 최적화 (Optimization for the Internal Structure of a Recuperator with Offset Strip Fins)

  • 도규형;한용식;최병일;김명배
    • 한국군사과학기술학회지
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    • 제14권6호
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    • pp.1178-1185
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    • 2011
  • In the present study, a recuperator is suggested to improve the thermal efficiency of a micro gas turbine. Primary design parameters of the recuperator are determined from the ideal cycle analysis. The counter flow plate-fin heat exchanger with offset strip fins is chosen as the type of the recuperator. In order to satisfy the design constraints which are the minimum effectiveness and the maximum pressure drop, the optimization for the internal structure of the recuperator is performed with varying the fin spacing and the fin height of offset strip fins. Also the effects of the thermal conductivity of fins and separation plates and the longitudinal heat conduction on the thermal performance of the recuperator are investigated.

Fundamental and plane wave solution in non-local bio-thermoelasticity diffusion theory

  • Kumar, Rajneesh;Ghangas, Suniti;Vashishth, Anil K.
    • Coupled systems mechanics
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    • 제10권1호
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    • pp.21-38
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    • 2021
  • This work is an attempt to design a dynamic model for a non local bio-thermoelastic medium with diffusion. The system of governing equations are formulated in terms of displacement vector field, chemical potential and the tissue temperature in the context of non local dual phase lag (NL DPL) theories of heat conduction and mass diffusion. Based on this considered model, we study the fundamental solution and propagation of plane harmonic waves in tissues. In order to analyze the behavior of the NL DPL model, we construct basic theorem in the terms of elementary function which determine the existence of three longitudinal and one transverse wave. The effects of various parameters on the characteristics of waves i.e., phase velocity and attenuation coefficients are elaborated by plotting various figures of physical quantities in the later part of the paper.

Characterization of Brain Microstructural Abnormalities in High Myopia Patients: A Preliminary Diffusion Kurtosis Imaging Study

  • Huihui Wang;Hongwei Wen;Jing Li;Qian Chen;Shanshan Li;Yanling Wang;Zhenchang Wang
    • Korean Journal of Radiology
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    • 제22권7호
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    • pp.1142-1151
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    • 2021
  • Objective: To evaluate microstructural damage in high myopia (HM) patients using 3T diffusion kurtosis imaging (DKI). Materials and Methods: This prospective study included 30 HM patients and 33 age- and sex-matched healthy controls (HCs) with DKI. Kurtosis parameters including kurtosis fractional anisotropy (FA), mean kurtosis (MK), axial kurtosis (AK), and radial kurtosis (RK) as well as diffusion metrics including FA, mean diffusivity, axial diffusivity (AD), and radial diffusivity derived from DKI were obtained. Group differences in these metrics were compared using tract-based spatial statistics. Partial correlation analysis was used to evaluate correlations between microstructural changes and disease duration. Results: Compared to HCs, HM patients showed significantly reduced AK, RK, MK, and FA and significantly increased AD, predominately in the bilateral corticospinal tract, right inferior longitudinal fasciculus, superior longitudinal fasciculus, inferior fronto-occipital fasciculus, and left thalamus (all p < 0.05, threshold-free cluster enhancement corrected). In addition, DKI-derived kurtosis parameters (AK, RK, and MK) had negative correlations (r = -0.448 to -0.376, all p < 0.05) and diffusion parameter (AD) had positive correlations (r = 0.372 to 0.409, all p < 0.05) with disease duration. Conclusion: HM patients showed microstructural alterations in the brain regions responsible for motor conduction and vision-related functions. DKI is useful for detecting white matter abnormalities in HM patients, which might be helpful for exploring and monitoring the pathogenesis of the disease.

SPS/용침 공정에 의한 W-Cu연속경사기능재료의 제초와 특성 (Fabrication and Characteristics of Continuous W-Cu FGM by SPS/Infiltration Process)

  • 신철균;석명진;오승탁;김지순;권영순
    • 한국분말재료학회지
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    • 제11권2호
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    • pp.158-164
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    • 2004
  • W-Cu composite has been used for the applications requiring both high strength, good thermal and electrical conductivity. A graded combination of W and Cu will reduce thermal stress concerned with heat conduction, maintaining good thermal conductivity and high mechanical strength. In the present work, an attempt was made to fabricate continuous W-Cu FGM by preparing the graded porous structure of W skeleton using spark plasma sintering (SPS) process followed by infiltrating Cu. The graded porous structure was prepared at 150$0^{\circ}C$ for 60s under pressure of 15MPa by SPS process using a graphite mold with varying crr)ss section in the longitudinal direction. Infiltration of Cu was performed at 115$0^{\circ}C$ for 1 hour under $H_2$. W-Cu composite with graded Cu composition of 14 to 27 wt% was finally prepared. In this process the gradient of composition could be conveniently controlled by varying the gradient of cross sectional area of graphite mold, temperature and pressure.