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1.
S. V. Narasimhan Nandini Basumallick Ratana Chaitanya 《Signal, Image and Video Processing》2008,2(3):261-274
In this paper, a new method for extracting the system phase from the bispectrum of the system output has been proposed. This
is based on the complete bispectral data computed in the frequency domain and modified group delay. The frequency domain bispectrum computation improves the frequency resolution and the modified
group delay reduces the variance preserving the frequency resolution. The use of full bispectral data also reduces the variance
as it is used for averaging. For the proposed method at a signal to noise ratio of 5dB, the reduction in root mean square
error is in the range of 1.5–7 times over the other methods considered. 相似文献
2.
Tuspon Thanpitcha Anuvat Sirivat Alexander M. Jamieson Ratana Rujiravanit 《应用聚合物科学杂志》2010,116(3):1626-1634
Blend films consisting of polyaniline in emeraldine base form (PANI EB) dispersed in partially cross‐linked carboxymethylchitin (CM‐chitin) were prepared by solution casting, and characterized for their physical, thermal, and electrical properties. Homogeneous and mechanically robust blend films were obtained having PANI EB contents up to 50 wt % in the CM‐chitin matrix. FTIR spectra confirm intimate mixing of the two blend components. The thermal stability of the blend films increased with increase of PANI EB content, suggesting the formation of an intermolecular interaction, such as hydrogen bonding, between PANI EB and CM‐chitin chains. The addition of PANI EB into the pure CM‐chitin film resulted in a decrease in electrical conductivity of the films owing to disruption of ionic conduction of the CM‐chitin structure. After doping the blend films by immersion in HCl solution, the electrical conductivity of the HCl‐doped films increased with increase of the PANI EB content to a maximum value of the order of 10?3 S/cm at 50 wt % PANI EB content. The electrical conductivity of the blend films was also dependent on the HCl concentration as well as on the type of acid dopant. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
3.
In this work, an efficient and simple method to graft a vinylsulfonic acid sodium salt on a poorly water‐soluble chitosan is described. Commercially available low molecular weight chitosan is converted to water‐soluble chitosan containing hyperbranched‐vinylsulfonic acid sodium salt groups. The process comprises the following steps: Michael addition of methyl acrylate, amidation with ethylenediamine, and Michael addition of vinylsulfonic acid sodium salt. A variety of chitosans containing vinylsulfonic acid sodium salt, with improved water solubility, is synthesized by repeating these three steps. The new chitosan derivatives show better antimicrobial activity against Micrococcus luteus ATCC 10240 and Achromobacter xylosoxidans ATCC 2706. In addition, they display better chelating behavior with heavy metals, like cadmium(II), copper(II), and nickel(II), than the starting chitosan. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
4.
Wichitpan Rongwong Ratana Jiraratananon Supakorn Atchariyawut 《Separation and Purification Technology》2009,69(1):118-125
The membrane wetting by the liquid absorbents is an important problem in the operation of gas–liquid membrane contacting process. In order to gain a better understanding on the role of absorbents on membrane wetting, monoethanolamine (MEA, primary amine), diethanolamine (DEA, secondary amine), and 2-amino-2-methyl-1-propanol (AMP, sterically hindred amine) were applied as absorbent solutions. The membrane used for the experiments was the hollow fiber polyvinylidenefluoride (PVDF) membrane. The performance of both single and mixed amine solutions on the CO2 absorption capacity and membrane wetting potential were investigated. In addition, sodium chloride (NaCl, inorganic salt) and sodium glycinate (SG, organic salt) were added into the MEA aqueous solution to observe CO2 flux and membrane wetting.The results revealed that the use of MEA solution and SG as absorbents gave highest CO2 flux. The overall mass transfer coefficients obtained from the experiments also showed the same trend as CO2 flux, i.e, the values were in the following order: MEA> AMP > DEA. However, the long-term flux was monitored and it was found that MEA also gave lowest flux decline due to the membrane wetting. The use of mixed amine solutions and the addition of NaCl did not help protect the membrane wetting. On the contrary, the addition of SG in to MEA solution can improve flux and resulted in stable CO2 flux indicating that the membrane wetting was negligible. 相似文献
5.
Panu Sukitpaneenit Tuspon Thanpitcha Anuvat Sirivat Christoph Weder Ratana Rujiravanit 《应用聚合物科学杂志》2007,106(6):4038-4046
Electrically conducting elastomer fibers based on natural rubber (NR) and up to 10% w/w polyaniline (PANI) in its emeraldine base (EB) form were fabricated by a wet spinning process. The resulting fibers at various PANI contents were doped by immersion in aqueous HCl solution, which converted the PANI to the electrically conductive emeraldine salt (ES) form. The morphology of the composite fibers was studied by scanning electron microscopy (SEM). PANI particles were inhomogeneously distributed in the NR matrix. The electrical conductivity of the fibers increased with the increasing PANI‐ES content and leveled off at a value of around 10?3 S/cm at PANI‐ES concentration of 5% w/w. The fibers retained most of their elasticity upon doping, while the tenacity was somewhat reduced. Gratifyingly, the electrical conductivity of the new elastomer fibers was preserved upon elongational deformation, even if strains as large as 600% were applied. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 相似文献
6.
Formation of W/O microemulsion based on natural glycolipid biosurfactant, mannosylerythritol lipid-a
Worakitkanchanakul W Imura T Morita T Fukuoka T Sakai H Abe M Rujiravanit R Chavadej S Kitamoto D 《Journal of oleo science》2008,57(1):55-59
Mannosylerythritol lipid-A (MEL-A) is a glycolipid biosurfactant abundantly produced from soybean oil by microorganisms at a yield of up to 100 g/L. In this study, the formation of water-in-oil (W/O) microemulsion based on the single component of MEL-A was confirmed using dynamic light scattering (DLS) and freeze fracture electron microscopy (FF-EM). DLS and FF-EM measurements revealed that the diameter of the microemulsion increases with an increase in water-to-surfactant mole ratio (W(0)) ranging from 20 to 60 nm, and the maximum W(0) value was found to be 20, which is as high as that of soybean lecithin. Glycolipid biosurfactant has a great potential for the formation of W/O microemulsion without using any cosurfactants. 相似文献
7.
Mengieng Ung Isaac Luginaah Ratana Chuenpagdee Gwyn Campbell 《The International journal of environmental studies》2017,74(2):325-339
Climate change contributes to the global burden of diseases and premature mortality. This burden may be even more pronounced in coastal areas amongst the poor and the marginalised groups. Using a survey data-set from 1823 households in coastal communities in Cambodia, we examine how perceptions on climate change impacts influence self-rated health (SRH) when controlling for livelihoods, food security and contextual and compositional factors. The findings show that individuals who had higher factor scores on perceived socio-ecological impact of climate change were less likely to report good SRH. Likewise, those who reported barriers to protect themselves against the impacts of climate change were less likely to report good health. Surprisingly, households that reported earning more were less likely to report good health. 相似文献
8.
Chemical and Cellular Antioxidant Activities of Chicken Breast Muscle Subjected to Various Thermal Treatments Followed by Simulated Gastrointestinal Digestion
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Papungkorn Sangsawad Ratana Kiatsongchai Benjamart Chitsomboon Jirawat Yongsawatdigul 《Journal of food science》2016,81(10):C2431-C2438
The effect of thermal treatments on chemical and cellular antioxidant activities of chicken breasts subjected to in vitro gastrointestinal digestion was investigated. Breast of Korat crossbred chicken (KC) and commercial broiler (BR) were cooked under various conditions, namely heating at 70 °C for 30 min (H‐0.5) and 24 h (H‐24), autoclaving (AC) at 121°C for 15 min (AC‐15) and 60 min (AC‐60). Protein digestibility decreased upon the extreme thermal treatment of AC‐60. The H‐0.5 improved metal chelating activity of KC digesta, FRAP, and anti‐liposome oxidation of BR digesta. Digesta of BR/H‐0.5 and KC/AC‐15 at 50 μg/mL exhibited the highest cytoprotective effect against tert‐butyl hydroperoxide (TBHP)‐induced oxidative damage of HepG2 cells. In addition, the KC/AC‐15 digesta at a concentration as low as 12.5 μg/mL inhibited intracellular TBHP‐induced reactive oxyfen species (ROS) production (P < 0.05). Thus, the digesta of KC breasts subjected to AC‐15 provides not only nutritional value but also antioxidant activity at the cellular level. 相似文献
9.
This work investigates the membrane modification to enhance hydrophobicity aiming for applications as membrane contactors. The PVDF membranes were activated by NaOH and by plasma activation followed by grafting using three organosilanes. For the NaOH, the contact angle of original membranes (68°) was decreased from 44° to 31° with increasing NaOH concentration from 2.5M to 7.5M at 60°C for 3 h. The contact angle of NaOH treated membranes was increased to 100° after modification with 0.01M FAS‐C8 for 24 h. A needle‐like structure was observed on the membrane surface while there was no significant change in pore size and pore size distribution. Moreover, FTIR and XPS data showed Si peak and composition. The mechanical strength was improved. The surface modified membranes under helium plasma activation followed by grafting with 0.01M FAS‐C8 for 24 h showed higher contact angle, mechanical strength and surface roughness than that obtained by NaOH activation method while other physical properties did not change. The long‐term performance test for 15 days of operation was conducted. The modified membranes exhibited good stability and durability for CO2 absorption. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
10.
Jirawut Junkasem Ratana Rujiravanit Brian P Grady Pitt Supaphol 《Polymer International》2010,59(1):85-91
Electrospinning is a facile method for preparing nanocomposite materials in fiber form. Nanomaterials that have been incorporated within such fibers are usually inorganic in nature. Recently, nanocomposite nanofibers based on poly(vinyl alcohol) (PVA) as the matrix and nanocrystals of α‐chitin (i.e. chitin whiskers; ca 31 nm in width and ca 549 nm in length on average) as the nanofiller have been successfully prepared. In the study reported here, the fibers were further investigated using X‐ray diffraction (XRD) and dynamic mechanical analyses in comparison with the corresponding solvent‐cast films. The average diameters of the PVA/chitin whiskers fibers ranged between 175 and 218 nm. Careful analysis of the wide‐angle XRD patterns of the fiber mats and the films showed that PVA was partially crystalline, and the incorporation of the whiskers within the fibers was confirmed by peaks characteristic to α‐chitin crystals. Dynamic mechanical analysis showed that the fiber mats were weaker than the films and that the relaxation temperatures associated with the glass transition (Tg) of the fiber mats were greater than those of the films. The addition and increasing the amount of the whiskers caused the crystallinity of PVA within the nanocomposite materials to decrease and Tg to increase. The present study shows that the geometry of nanocomposite materials plays a major role in determining their properties. Copyright © 2009 Society of Chemical Industry 相似文献