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181.
Kallath Hariharan Lee Jun Seok Kholi Foster Kwame Ha Man Yeong Min June Kee 《Journal of Mechanical Science and Technology》2021,35(3):1075-1086
Journal of Mechanical Science and Technology - Here, a distinct procedure was adopted to optimize the shape of the NACA 0012 airfoil profile for Reynolds number, Mach number, and angle of attack... 相似文献
182.
Synthesis of Transesterified Palm Olein‐Based Polyol and Rigid Polyurethanes from this Polyol
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![点击此处可从《Journal of the American Oil Chemists](/ch/ext_images/free.gif)
Mohd Zan Arniza Seng Soi Hoong Zainab Idris Shoot Kian Yeong Hazimah Abu Hassan Ahmad Kushairi Din Yuen May Choo 《Journal of the American Oil Chemists' Society》2015,92(2):243-255
Transesterification of palm olein with glycerol can increase the functionality by introducing additional hydroxyl groups to the triglyceride structure, an advantage compared to using palm olein directly as feedstock for producing palm‐based polyol. The objective of this study was to synthesize transesterified palm olein‐based polyol via a three‐step reaction: (1) transesterification of palm olein, (2) epoxidation and (3) epoxide ring opening. Transesterification of palm olein yielded approximately 78 % monoglyceride and has an hydroxyl value of approximately 164 mg KOH g?1. The effect of formic acid and hydrogen peroxide concentrations on the epoxidation reaction was studied. The relationships between epoxide ring‐opening reaction time and residual oxirane oxygen content and hydroxyl value were monitored. The synthesized transesterified palm olein‐based polyol has hydroxyl value between 300 and 330 mg KOH g?1 and average molecular weight between 1,000 and 1,100 Da. On the basis of the hydroxyl value and average molecular weight of the polyol, the transesterified palm olein‐based polyol is suitable for producing rigid polyurethane foam, which can be designed to exhibit desirable properties. Rigid polyurethane foams were synthesized by substituting a portion of petroleum‐based polyol with the transesterified palm olein‐based polyol. It was observed that by increasing the amount of transesterified palm olein‐based polyol, the core density and compressive strength were reduced but at the same time the insulation properties of the rigid polyurethane foam were improved. 相似文献
183.
Yoonho Choi Myung-Jin Choi Song-Hyun Cha Yeong Shik Kim Seonho Cho Youmie Park 《Nanoscale research letters》2014,9(1):103
An eco-friendly approach is described for the green synthesis of gold nanoparticles using catechin as a reducing and capping agent. The reaction occurred at room temperature within 1 h without the use of any external energy and an excellent yield (99%) was obtained, as determined by inductively coupled plasma mass spectrometry. Various shapes of gold nanoparticles with an estimated diameter of 16.6 nm were green-synthesized. Notably, the capping of freshly synthesized gold nanoparticles by catechin was clearly visualized with the aid of microscopic techniques, including high-resolution transmission electron microscopy, atomic force microscopy, and field emission scanning electron microscopy. Strong peaks in the X-ray diffraction pattern of the as-prepared gold nanoparticles confirmed their crystalline nature. The catalytic activity of the as-prepared gold nanoparticles was observed in the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH4. The results suggest that the newly prepared gold nanoparticles have potential uses in catalysis. 相似文献
184.
Seong Yeong Kim Sang Hyek Kim Kwang-Soon Shin Ho Lee 《Food science and biotechnology》2010,19(3):803-808
In order to develop the new physiologically active materials from the leaves of Panax ginseng C.A. Meyer, the ginsenoside-rich fraction (GL-1) was isolated from ginseng leaves and physiological activities were examined.
GL-1 contained crude saponin (ginsenosides, 58.00%) and component ginsenoside analysis using high performance liquid chromatography
(HPLC) showed that the major ginsenosides of GL-1 were Re, Rg1, Rc, and F2 and their contents were 34.42, 20.73, 18.42, and
8.60%, respectively. ABTS and DPPH radical scavenging activities of GL-1 were 75.14 and 39.28% at 10,000 μg/mL, respectively.
Superoxide anion radical scavenging activity was 70.94% at 1,000 μg/mL. GL-1 also expressed the considerable anti-complementary
activity in dose-dependent manner. Results obtained by crossed immunoelectrophoresis using anti-human C3 and anti-complementary
activity in the absence of Ca++ ion suggested that complement activation by GL-1 from ginseng leaves occur via both alternative and classical pathways. 相似文献
185.
We fabricated the vertically-aligned zinc oxide (ZnO)/silicon (Si) double nanostructures by simple processes using the metal-assisted chemical etching and a subsequent hydrothermal synthesis, and their optical property was investigated. For efficient antireflection characteristics, Si nanostructures were optimized by changing the size of the dewetted silver (Ag) at different etching times. The thermally dewetted Ag nanoparticles or semi-island films as metal catalysts were controlled by the Ag film thickness and dewetting temperature. To form the ZnO/Si double nanostructures, ZnO nanorods were synthesized on the chemically etched Si nanostructures using a thin sputtered ZnO seed layer. The grown ZnO nanorod arrays (NRAs) exhibited good crystallinity and further reduced the surface reflection due to their antireflective property. The ZnO/Si double nanostructures showed the increased peak intensity of X-ray diffraction as well as the significantly reduced solar weight reflectance of 6.05% compared to 11.71% in the ZnO NRAs on the flat Si substrate. Also, the enhanced antireflection property of ZnO/Si double nanostructures was theoretically analyzed by performing the rigorous coupled wave analysis simulation. 相似文献
186.
187.
We propose a new matched filter architecture for chirp spread spectrum in IEEE 802.15.4a. By using relations among the four subchirps, the proposed architecture comprises four subfilters utilizing only a set of coefficients matched to the first subchirp. The four subfilters share adders and registers, and as a result, the required adders and registers for implementation are reduced. 相似文献
188.
189.
Eun Mi Kim Man Ho Han Young Jae Lee Du Hyun Song Hyun Kyu Lee Oh Wook Kwon Dong Soo Shin Sung Soo Han Seok Kyun Noh Jae Kyun Shin Yeong‐Soon Gal Won Seok Lyoo 《应用聚合物科学杂志》2007,106(5):3259-3267
The effects of three major molecular parameters of poly(vinyl alcohol)—the number‐average degree of polymerization, degree of saponification, and syndiotactic dyad content—on the characteristics of poly(vinyl alcohol) films were investigated. Various poly(vinyl alcohol) films were prepared by a casting method. Then, the films were characterized with atomic force microscopy, differential scanning calorimetry, wide‐angle X‐ray diffraction, Fourier transform infrared spectroscopy, and Instron instrumentation. On the basis of atomic force microscopy images and calculated average roughness values, it was determined that the surface roughness of poly(vinyl alcohol) films increased with increasing molecular parameters. The crystallinities obtained with differential scanning calorimetry and wide‐angle X‐ray diffraction analyses were also enhanced with increasing molecular parameters, especially the degree of saponification. The tensile properties were improved with higher molecular parameters. This might be ascribed to the fact that the higher the molecular parameters were, the stronger the hydrogen bonding was. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
190.
A proposed variable parameter control chart for monitoring the multivariate coefficient of variation
XinYing Chew Michael Boon Chong Khoo Khai Wah Khaw Wai Chung Yeong Zhi Lin Chong 《Quality and Reliability Engineering International》2019,35(7):2442-2461
An efficient process monitoring system is important for achieving sustainable manufacturing. The control charting technique is one of the most effective techniques to monitor process quality. In certain processes where the process mean and variance are not independent of one another, the coefficient of variation (CV), which measures the ratio of the standard deviation to the mean, should be monitored. In line with industrial settings, where at least two or more variables are monitored simultaneously in most processes, this paper proposes a variable parameter (VP) chart to monitor the multivariate CV (MCV). Formulae and algorithms to optimize the various performance measures are discussed. The proposed VP MCV chart is designed based on a Markov chain approach. The performance comparison shows that the proposed VP MCV chart prevails over the existing MCV charts, in terms of the average time to signal (ATS), standard deviation of the time of signal (SDTS), and expected average time to signal (EATS) criteria. An example is presented to illustrate the implementation of the proposed VP MCV chart. 相似文献