• 제목/요약/키워드: SZ effect

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5052 알루미늄 합금 마찰교반접합부 특성에 미치는 접합인자의 영향 (Effect of Welding Parameters on the Friction Stir Weldability of 5052 Al alloy)

  • 이원배;김상원;이창용;연윤모;장웅성;서창제;정승부
    • Journal of Welding and Joining
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    • 제22권3호
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    • pp.69-76
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    • 2004
  • Effects of friction stir welding parameters such as tool rotation speed and welding speed on the joints properties of 5052 Al alloys were studied in this study. A wide range of friction stir welding conditions could be applied to join 5052 AA alloy without defects in the weld zone except for certain welding conditions with a lower heat input. Microstructures near the weld zone showed general weld structures such as stir zone (SZ), thermo-mechanically affected zone (TMAZ) and heat affected zone (HAZ). Each zone showed the dynamically recrystallized grain, transient grain and structure similar to base metal's, respectively. Hardness distribution near the weld zone represented a similar value of the base metal under wide welding conditions. However, in case of 800 rpm of tool rotation speed, hardness of the stir zone had a higher value due to the fine grain with lots of dislocation tangle, a higher angle grain boundary and some of Al3Fe particles. Except joints with weld defects, tensile strength and elongation of the joints had values similar to the base metal values and fracture always occurred in the regions approximately 5mm away from the weld center.

The Impact of Capital Structure on Firm Value: A Case Study in Vietnam

  • LUU, Duc Huu
    • The Journal of Asian Finance, Economics and Business
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    • 제8권5호
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    • pp.287-292
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    • 2021
  • The article analyzes the impact of capital structure on the firm value of chemical companies listed on the stock market of Vietnam. Data was collected from the financial statements of 23 chemical firms listed on the Vietnam stock market from 2012 to 2019. Quantitative research method with regression model according to OLS, FEM, REM method is used; FGLS method is used to overcome the model's defects. In this research, firm value (Tobin's Q) is a dependent variable. Capital structure (DA), Return on assets (ROA), Asset turnover (AT), fixed assets (TANG), Solvency (CR), Firm size (SZ), Firm Age (AGE), and revenue growth rate (GR) are independent variables in the study. The analysis results show that the capital structure of firms in the chemical industry listed on the Vietnam stock market has an inverse correlation with firm value. Besides, firms with greater asset turnover, business size, and number of years of operation have lower firm value. This article helps corporate executives improve corporate value by adjusting their capital structure properly. Chemical firms adjusted their capital structure in the direction of gradually decreasing the debt ratio and gradually increasing equity. Firms use high debt, which has the effect of reducing the firm value of firms in the chemical industry.

Multi-wavelength view of SPT-CL J2106-5844: A massive galaxy cluster merger at z~1.13

  • Kim, HyeongHan;Di Mascolo, Luca;Mroczkowski, Tony;Perrott, Yvette;Rudnick, Lawrence;Jee, M. James;Churazov, Eugene;Collier, Jordan D.;Diego, Jose M.;Hopkins, Andrew M.;Kim, Jinhyub;Koribalski, Barbel S.;Marvil, Joshua D.;van der Burg, Remco;West, Jennifer L.
    • 천문학회보
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    • 제46권1호
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    • pp.34.2-34.2
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    • 2021
  • SPT-CL J2106-5844 is the most massive galaxy cluster at z>1 discovered to date. It has been known to be an isolated system with a singular, well-defined halo. However, recent studies provide lines of evidence for its merging state. We strengthen the case with the multi-wavelength observations from ALMA, ACA, ASKAP, ATCA, and Chandra. With the sensitive, high resolution ALMA+ACA observations, we reconstruct the ICM pressure map from the thermal SZ effect. It reveals two main gas components that are associated with the mass clumps inferred from the weak-lensing analysis. Furthermore, the X-ray hardness map supports the bimodal gas distribution. With these multi-wavelength data, we probe the merger phase in SPT-CL J2106-5844.

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대두올리고당이 당뇨 유발 흰쥐의 혈당 및 지질대상에 미치는 영향 (Effects of Soyoligosaccharides on Blood glucose and Lipid Metabolism in Streptozotocin-Induced Diabetic Rats)

  • 김미현;김혜영;김우경;김지영;김숙희
    • Journal of Nutrition and Health
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    • 제34권1호
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    • pp.3-13
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    • 2001
  • This study was conducted to investigate the effect of soyligosaccharides on improvement of diabetes mellitus. Sprague Dawley rats were divided into three groups. Control and one experimental group were fel AIN-93G diet(mixed diet) and the other experimental group was fed a similar diet containing 5% soyligosaccharides(oligosaccharide diet) for 6 weeks. Experimental groups were divided into two sub-groups after streptozotocin(STZ) injection and fed th mixed diet or the oligosaccharide diet for the next 2 weeks. Followings are final experimental and control groups: MM (mixed dietlongrightarrowSTZ injectionlongrightarrowmixed diet). MO(mixed dietlongrightarrowSTZ injectionlongrightarrowoligosaccharide diet), OM( oligosaccharide dietlongrightarrowSTZ injectionlongrightarrowmixed diet), OO(oligosaccharide dietlongrightarrowSTZ injectionlongrightarrowoligosaccharide diet), C(mixed dietlongrightarrowplacebo injectionlongrightarrowmixed diet). Blood glucose was analyzed at d1, d8 and d12 after streptozotocin injection. At the end of the experimental period, fecal bifidobacteria, plasma insulin, total lipid, triglyceride, cholesterol, and leptin concentrations was analyzed, After STZ injection, blood glucose level was significantly elevated in experimental group compared to a control group. Elevated blood glucose level declined faster in OO group compared to the other experimental groups. Meanwhile, insulin concentration decreased in all experimental groups compared to a control group. The number of bifidobacteria was significantly increased in oligosaccharide diet groups after STZ injection (MO and OO) than a mixed diet group(MM). Plasma cholesterol concentration significantly decreased in oligosaccharide diet groups(MO and OO) compared to mixed diet groups (MM and OM) after SZ injection. Plasma triglyceride and liver cholesterol concentrations significantly decreased in MO group compared to other experimental groups. Meanwhile, plasma leptin concentration was significantly lower in oligosaccharide diet groups after STZ injection(MO and OO) compared to a control group. The results in this study suggest that the dietary soyoligosaccharides has strong on reduction of reduction of blood glucose and lipid concentrations in streptozotoicin-induced diabetic rats. Thus, the use of soyoligosaccharides at a diet for IDDM patients may help to improve diabetes mellitus symptoms.(Korean J Nutrition 34(1) : 3-13, 2001)

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W92-Ni-Fe 소결툴을 이용한 Cu-Ni 합금의 용접부미세조직과 경도 특성 (Investigation for Microstructure and Hardness of Welded Zone of Cu-Ni Alloy using W92-Ni-Fe Sintering Tool)

  • 윤태진;박상원;강명창;노중석;정성욱;강정윤
    • 한국분말재료학회지
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    • 제22권3호
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    • pp.181-186
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    • 2015
  • In this study, the effect of the friction stir welding (FSW) was compared with that of the gas tungsten arc welding (GTAW) on the microstructure and microhardness of Cu-Ni alloy weldment. The weldment of 10 mm thickness was fabricated by FSW and GTAW, respectively. Both weldments were compared with each other by optical microstructure, microhardness test and grain size measurement. Results of this study suggest that the microhardness decreased from the base metal (BM) to the heat affected zone (HAZ) and increased at fusion zone (FZ) of GTAW and stir zone (SZ) of FSW. the minimum Hv value of both weldment was obtained at HAZ, respectively, which represents the softening zone, whereas Hv value of FSW weldment was little higher than that of GTAW weldment. These phenomena can be explained by the grain size difference between HAZs of each weldment. Grain size was increased at the HAZ during FSW and GTAW. Because FSW is a solid-state joining process obtaining the lower heat-input generated by rotating shoulder than heat generated in the arc of GTAW.

Laser-FSW Hybrid 접합기술을 적용한 이종재료(Al6061-T6/SS400) 접합부의 접합성 및 기계적 특성에 관한 연구 (A Study on the Weldability and Mechanical Characteristics of Dissimilar Materials Butt Joints by Laser Assisted Friction Stir Welding)

  • 방한서;방희선;김현수;김준형;오익현;노찬승
    • Journal of Welding and Joining
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    • 제28권6호
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    • pp.70-75
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    • 2010
  • This study intends to investigate the weldability and mechanical characteristics of butt weld joints by LAFSW for dissimilar materials (Al6061-T6 and SS400). At optimum welding conditions, the tensile strength of dissimilar materials joints made by FSW is found to be lower than that of LAFSW. Due to the increase in plastic flow and formation of finer recrystallized grains at the TMAZ and SZ by laser preheating in LAFSW, the hardness in LAFSW appeared to be higher than that of FSW. Compared with FSW, finer grain size is observed and elongated grains in parent metal are deformed in the same direction around the nugget zone in TMAZ of Al6061-T6 by LAFSW. Whereas, at weld nugget zone, coarse grain size is appeared in LAFSW compared to FSW, which is owing to more plastic flow due to laser preheating effect. In dissimilar materials joints by LAFSW, ductile mode of fracture is found to occur at Al6061 side with fewer brittle particles. Mixed mode of cleavage area and ductile fracture is observed at SS400 side.

The Effect of a Natural Zeolite (Clinoptilolite) on the Performance of Broiler Chickens and the Quality of Their Litter

  • Karamanlis, X.;Fortomaris, P.;Arsenos, G.;Dosis, I.;Papaioannou, D.;Batzios, C.;Kamarianos, A.
    • Asian-Australasian Journal of Animal Sciences
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    • 제21권11호
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    • pp.1642-1650
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    • 2008
  • The objective of this study was to assess the effect of clinoptilolite (a natural zeolite) on growth and performance of broilers as well as on the quality of their litter. A total of 5,200 one-day old broiler chickens (Cobb 500) were used in two consecutive rounds lasting 42 days each. The broilers were given free and continuous access to a nutritionally non-limiting diet (in meal form) that was either a basal diet (B) or a 'zeolite diet' (Z; the basal diet supplemented with clinoptilolite at a level of 2%). A $2{\times}2$ factorial design consisted of two feeding treatments (B and Z) and two bedding types, sawdust (S) and sawdust with zeolite (Sz, which was the result of adding $2kg\;zeolite/m^2$), was used. In each round the broilers were randomly assigned to one of four (n = 650), treatment groups: two fed on the basal diet (B) and had bedding of either sawdust (group BS) or sawdust and zeolite (group BSz) and two fed on the Z diet and had as bedding either sawdust (ZS) or sawdust and zeolite (ZSz). Average growth rates were significantly (p<0.05) different between broilers of different groups; broilers that were fed on the 'zeolite diet' (Z) and were placed either in a compartment with sawdust bedding or sawdust bedding and zeolite (ZS and ZSz) as well those that were fed on the basal diet in a compartment with sawdust bedding and zeolite (BSz) grew at a faster rate (p<0.05) compared with those of the control group (BS). The incorporation of NZ in broilers diets and in their bedding material decreased the organic content in litter samples throughout the experimental period. The lowest organic content was recorded in group ZSz where NZ was added in both feed and litter. Mean ammonia concentration (ppm) was significantly higher in group ZS in comparison to groups BSz and ZSz (27.00 vs. 20.55 and 21.71 respectively). The results of this study showed that the incorporation of the clinoptilolite both in feed and into the litter had a positive effect on broiler growth and also on the quality of their litter.

얕은 심도 VS주상도를 활용한 VS30 예측 방법론 비교 및 최적 계수 제시 (Comparison of Methods Predicting VS30 from Shallow VS Profiles and Suggestion of Optimized Coefficients)

  • 최인혁;곽동엽
    • 한국지반공학회논문집
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    • 제36권3호
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    • pp.15-23
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    • 2020
  • 지표면에서의 지반운동을 예측하는 지반운동예측모델은 30m까지의 평균전단파속도인 VS30을 부지효과를 나타내는 주요한 변수로 사용한다. VS30은 만약 VS주상도 깊이(z)가 30m 이상이면 주상도로부터 바로 계산할 수 있다. 하지만, 모든 부지에서 z가 30m 까지 있는 것은 아니다. 따라서, z < 30m일 경우 30m까지 연장하는 모델로부터 VS30을 예측할 필요가 있다. 이번 연구에서는 국내 지반 환경에 맞게 z가 30m 미만인 부지에서 VS30을 추정하는 예측 모델에 대한 새로운 계수를 제안하였다. 분석 자료로 기상청과 국토지반정보 통합DB센터에서 획득한 297개의 VS주상도를 활용하였고, 선행연구에서 제안한 식의 계수들을 회귀분석을 통해 새롭게 제시하였다. 분석 결과, z ≥ 15m 일 경우 대수로그 잔차의 표준편차가 약 0.061이내이므로 신뢰성 높은 VS30를 예측하는 것으로 확인하였다. z < 15m 일 경우 σ가 계속 증가하며, z = 5m일 경우 σ = 0.1으로 나타났다. 따라서, 매우 얕은 심도의 VS주상도를 모델에 적용하는 경우 주의를 요하며, 가능하다면 30m깊이까지 지반조사를 실시하여 VS30을 계산하는 것을 추천한다.

상아질접착제에 대한 광조사가 접착에 미치는 영향 (INFLUENCE OF LIGHT IRRADIATION OVER SELF-PRIMING ADHESIVE ON DENTIN BONDING)

  • 류현욱;김기옥;김성교
    • Restorative Dentistry and Endodontics
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    • 제26권5호
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    • pp.409-417
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    • 2001
  • 상아질접착제의 광조사가 상아질접착에 미치는 영향을 알아보기 위하여 in vitro에서 접착실험을 하였다. 120개의 발거된 소의 전치 협면 상아질을 노출시키고 산 부식 한 다음 self-priming형 상아질접착제 Prime&Bond$^{\circledR}$NT (Dentsply DeTrey, GmbH, Konstanz, Germany)를 도포 하였으며 600 mW/$\textrm{cm}^2$의 일반광도 또는 1930 mW/$\textrm{cm}^2$의 초고광도 광조사를 각각 20초 및 3초간 시행한 군과 시행하지 않은 군으로 나누어 복합레진 첨가후 광조사하였다. 접착제에 대한 광조사를 시행하지 않은 경우에는 복합레진 첨가 후 초고광도로 3초, 6초 및 12초간 광조사하였다. 접착양상 평가를 위해 만능시험기로 전단접착강도를 측정하고 파단면을 입체 현미경으로 관찰한 바를 일원 및 이원 변량분석법과 카이제곱검사법으로 통계 분석하여 다음과 같은 결과를 얻었다. 1. 상아질접착제를 광조사한 군이 광조사하지 않은 군에 비해 유의하게 높은 전단접 착강도를 나타내었다 (p<0.05). 2. 일반 광도 및 초고광도 광조사에 따른 전단접착강도에는 유의한 차이가 나타나지 않았다 (p>0.05). 3. 상아질접착제를 광조사하지 않고 복합레진 첨가 후 초고광도로 광조사한 군간에 조사시간에 따른 전단접착강도에는 유의 한 차이가 나타나지 않았다 (p>0.05). 4. 파단면 관찰 결과, 모든 군에서 접착계면에서의 파절을 포함하는 혼합파단양상이 가장 많이 나타났으며 군간에는 유의한 차이가 없었다 (p>0.05).

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광조사 방식이 복합레진 수복물의 변연누출에 미치는 영향 (EFFECT OF LIGHT IRRADIATION MODES ON THE MARGINAL LEAKAGE OF COMPOSITE RESIN RESTORATION)

  • 박은숙;김기옥;김성교
    • Restorative Dentistry and Endodontics
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    • 제26권4호
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    • pp.263-272
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    • 2001
  • 저광도 중합법, 펄스 지연 중합법, 초고광도 중합법 등의 광조사 방식이 광중합형 복합레진 수복물에서의 중합수축 응력에 미치는 영향을 알아보기 위해 in vitro에서 미세 누출 실험을 하였다. 80개의 발거된 소구치의 협측면에 5급 와동을 형성하고, 600mW/$cm^2$로 30초간 광조사하는 보통 광도 중합군, 300mW/$cm^2$로 60초간 광조사하는 저광도 중합군, 400mW/$cm^2$로 2초간 광조사하고 5분간 기다린 후 800mW/$cm^2$로 10초간 최종 중합시키는 펄스-지연 중합군, 그리고 1930mW/$cm^2$의 광도로 3초간 광조사하는 초고광도 중합군 등의 4개의 군으로 나누어 hybrid 형의 광중합복합레진을 충전하고 각 군의 방법대로 중합한 후, 변연의 0.5mm 외부에 nail varnish를 도포하고 37$^{\circ}C$, 2% metylene blue 용액에 24시간 동안 침적시켰다. 시편을 아크릴릭 레진에 매몰한 후 수복물의 중앙에서 종절단하여 입체현미경하에서 그 단면을 관찰한 후 법랑질과 상아질 변연으로 나누어 색소의 침투도를 측정하여 다음과 같은 결과를 얻었다. 1. 펄스 지연 중합군의 색소 침투도는 법랑질과 상아질 변연 모두에서 보통광도, 저광도 및 초고광도 중합군과 유의한 차이를 보이지 않았다(p>0.05). 2. 상아질 변연에서 초고광도 중합군은 보통광도 중합군과 저광도 중합군에 비해 유의하게 높은 색소 침투도를 보였다(p<0.05). 3. 법랑질 변연에서의 4개 군의 색소 침투도는 서로 유의한 차이를 보이지 않았다(p>0.05). 4. 모든 군에서 상아질 변연에서의 색소 침투도는 법랑질군에서의 색소 침투도에 비해 유의하게 높았다(p<0.05).

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