• Journal of Welding and Joining
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• v.22 no.3
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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 Journal of Asian Finance, Economics and Business
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• v.8 no.5
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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.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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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.

• Journal of Nutrition and Health
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• v.34 no.1
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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)

• Journal of Powder Materials
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• v.22 no.3
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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.

• Journal of Welding and Joining
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• v.28 no.6
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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.

• Asian-Australasian Journal of Animal Sciences
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• v.21 no.11
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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.

• Journal of the Korean Geotechnical Society
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• v.36 no.3
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• pp.15-23
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• 2020

Ground motion models predicting intensity measures on surface use a time-averaged shear wave velocity, V_S30, as a key variable simulating site effect. The V_S30 can be directly estimated from V_S profiles if the profile depth (z) is greater than or equal to 30 m. However, some sites have V_S profiles with z < 30 m. In this case V_S30 can be predicted using extension models. This study proposes new coefficient sets for existing prediction equations using 297 Korea V_S profiles. We have collected V_S profiles from KMA and Geoinfo database. Fitting six existing methods to data, we suggest new coefficients for each method and evaluate their performance. It turns out that if z ≥ 15 m, the standard deviation (σ) of residual in log₁₀ is 0.061, which indicates that the estimated V_S30 is nearly accurate. If z < 15 m, the σ keeps increasing up to 0.1 for z = 5 m, so we caution the use of models at very low z. Nonetheless, we recommend investigating up to 30 m depth for V_S30 calculation if possible.

• Restorative Dentistry and Endodontics
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• v.26 no.5
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• pp.409-417
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• 2001

The purpose of this study was to investigate the influence of light irradiation over self-priming adhesive on dentin bonding. After acid etching the exposed dentin, a self-priming adhesive (Prime&Bond$^{\circledR}$NT dental adhesive system Dentsply DeTrey, GmbH, Konstanz, Germany) was applied and light irradiation was done for 20 sec with regular intensity (600 mW/$\textrm{cm}^2$) in group I and for 3 sec with ultra-high intensity (1930 mW/$\textrm{cm}^2$) in group III. No light irradiation was done over self-priming adhesive in groups II and IV. Composite resin was added on the self-priming adhesive and irradiated for 40 sec with regular intensity (600 mW/$\textrm{cm}^2$) in groups I and II and for 3 sec with ultra-high intensity (1930 mW/$\textrm{cm}^2$) in groups III and IV. To see the effect of light curing time on dentin bonding, another 3 group specimens were prepared. Without light-irradiation over self-priming adhesive, added composite resin was irradiated for 3, 6, or 12 sec with ultra-high intensity light. After bonded specimens were stored in 37$^{\circ}C$ distilled water for 24 hours, shear bond strength were measured using a universal testing machine (4202, Instron, Instron Co., U.S.A.) and fractured surfaces were examined under a stereomicroscope (SZ-PT Olympus, Japan). Statistical analysis were done with one-way, two-way ANOVA and chi-square test. The results were as follows : 1. The shear bond strengths from the groups irradiated over self-priming adhesive were significantly higher than those from the groups without irradiation (p<0.05). 2. There was no significant shear bond strength difference between regular intensity light irradiation groups and ultra-high intensity ones (p>0.05). 3. There was no significant shear bond strength difference among various irradiation time groups with ultra-high intensity ones (p>0.05). 4. In stereomicroscopic examination of fractured surfaces, adhesive-cohesive mixed failure mode was mostly seen in all groups, and there was no significant difference in failure mode among groups (p>0.05).

• Restorative Dentistry and Endodontics
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• v.26 no.4
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• pp.263-272
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• 2001

The aim of this study was to investigate the influence of four different light curing modes on the marginal leakage of Class V composite resin restoration. Eighty extracted human premolars were used. Wedge-shaped class Y cavities were prepared on the buccal surface of the tooth with high-speed diamond bur without bevel. The cavities were positioned half of the cavity above and half beyond the cemento-enamel junction. The depth, height, and width of the cavity were 2 mm, 3 mm and 2 mm respectively. The specimens were divided into 4 groups of 20 teeth each. All the specimen cavities were treated with Prime & Bond$^{R}$ NT dental adhesive system (Dentsply DeTrey GmbH, Germany) according to the manufacturer's instructions and cured for 10 seconds except group VI which were cured for 3 seconds. All the cavities were restored with resin composite Spectrum$^{TM}$ TPH A2 (Dentsply DeTrey GmbH, Germany) in a bulk. Resin composites were light-cured under 4 different modes. A regular intensity group (600 mW/${cm}^2$, group I) was irradiated for 30 s, a low intensity group (300 mW/${cm}^2$, group II) for 60 s and a ultra-high intensity group (1930 mW/${cm}^2$, group IV) for 3 s. A pulse-delay group (group III) was irradiated with 400 mW/${cm}^2$ for 2 s followed by 800 mW/${cm}^2$ for 10 s after 5 minutes delay. The Spectrum$^{TM}$ 800 (Dentsply DeTrey GmbH, Germany) light-curing units were used for groups I, II and III and Apollo 95E (DMD, U.S.A.) was used for group IV. The composite resin specimens were finished and polished immediately after light curing except group III which were finished and polished during delaying time. Specimens were stored in a physiologic saline solution at 37$^{\circ}C$ for 24 hours. After thermocycling (500$\times$, 5-55$^{\circ}C$), all teeth were covered with nail varnish up to 0.5 mm from the margins of the restorations, immersed in 37$^{\circ}C$, 2% methylene blue solution for 24 hours, and rinsed with tap water for 24 hours. After embedding in clear resin, the specimens were sectioned with a water-cooled diamond saw (Isomet$^{TM}$, Buehler Co., Lake Bluff, IL, U.S.A.) along the longitudinal axis of the tooth so as to pass the center of the restorations. The cut surfaces were examined under a stereomicroscope (SZ-PT Olympus, Japan) at ${\times}$25 magnification, and the images were captured with a CCD camera (GP-KR222, Panasonic, Japan) and stored in a computer with Studio Grabber program. Dye penetration depth at the restoration/dentin and the restoration/enamel interfaces was measured as a rate of the entire depth of the restoration using a software (Scion image, Scion Corp., U.S.A.) The data were analysed statistically using One-way ANOVA and Tukey's method. The results were as follows : 1. Pulse-Delay group did not show any significant difference in dye penetration rate from other groups at enamel and dentin margins (p>0.05) 2. At dentin margin, ultra-high intensity group showed significantly higher dye penetration rate than both regular intensity group and low intensity group (p<0.05). 3. At enamel margin, there were no statistically significant difference among four groups (p>0.05). 4. Dentin margin showed significantly higher dye penetration rate than enamel margin in all groups (p<0.05).