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11.
Steve Lien‐Chung Hsu Keng‐Chuan Chang Yuan‐Pin Huang Shih‐Jung Tsai 《应用聚合物科学杂志》2003,88(10):2388-2391
A poly(imide benzoxazole) was prepared directly from trimellitic anhydride chloride and 2,2‐bis(3‐amino‐4‐hydroxyphenyl)hexafluoropropane (BisAPAF) monomers in a two‐step method. In the first step, a poly(hydroxyamide amic acid) precursor was synthesized by the low‐temperature solution polymerization in an organic solvent. Subsequently, thermal cyclodehydration of the poly(hydroxyamide amic acid) precursor at 350°C produced the corresponding poly(imide benzoxazole). The inherent viscosity of the precursor polymer was 0.22 dL/g. The cyclized poly(imide benzoxazole) showed a glass transition temperature (Tg) at 329°C and a 5% weight loss temperature at 530°C in nitrogen and at 525°C in air. The poly(imide benzoxazole) is amorphous as evidenced by the wide‐angle X‐ray diffraction measurement. The structures of the precursor polymer and the fully cyclized polymer were characterized by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance spectroscopy (1H NMR). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2388–2391, 2003 相似文献
12.
The present study was designed to determine if dietary supply of long-chain fatty acid (LCFA, C20∶4n-6, and/or C22∶6n-3),
reflecting levels that might be incorporated into infant formulas, influences the fatty acid composition of the visual cell
membrane. The rod outer segment (ROS) of the retina was analyzed from rats fed diets varying in the ratio of 18∶2n-6 to 18∶3n-3
with or without 20∶4n-6 [arachidonic acid (AA)] and 22∶6n-3 (docosahexaenoic acid) from birth to six weeks of age. The level
of very long chain fatty acids (VLCFA, C24−C36) was identified using gas chromatography and gas chromatography-mass spectrometry. In the ROS, the highest relative percent
of AA was attained in phosphatidylcholine (PC) and phosphatidylethanolamine (PE) of animals fed 1% AA diet, whereas feeding
0.7% docosahexaenoic acid (DHA) diet significantly increased the DHA level in PC, phosphatidylserine, and phosphatidylinositol
compared to feeding diets containing AA. VLCFA of n-6 and n-3 up to C36 were found in PC, with the most abundant fatty acids being C32 and C34. In PC, phosphatidylserine and PE, the n-6 tetraenoic VLCFA level was highly increased in animals fed 1% AA compared to other
dietary groups. This study suggests that dietary fat containing small amounts of AA or DHA is an important factor influencing
membrane fatty acid composition of the visual cell during development.
Based on a presentation at the AOCS Annual Meeting & Expo in San Antonio, Texas, May 7–11, 1995. 相似文献
13.
DSC thermal analysis and X‐ray diffraction have been used to investigate the isothermal crystallization behavior and crystalline structure of nylon 6/clay nanocomposites. Nylon 6/clay has prepared by the intercalation of ε‐caprolactam and then exfoliating the layered silicates by subsequent polymerization. The DSC isothermal results reveal that introducing saponite into the nylon structure causes strongly heterogeneous nucleation induced change of the crystal growth process from a two‐dimensional crystal growth to a three dimensional spherulitic growth. But the crystal growth mechanism of nylon/montmorillonite nanocomposites is a mixed two‐dimensional and three‐dimensional spherulitic growth. The activation energy drastically decreases with the presence of 2.5 wt % clay in nylon/clay nanocomposites and then slightly increases with increasing clay content. The result indicates that the addition of clay into nylon induces the heterogeneous nucleation (a lower ΔE) at lower clay content and then reduces the transportation ability of polymer chains during crystallization processes at higher clay content (a higher ΔE). The correlation among crystallization kinetics, melting behavior, and crystalline structure of nylon/clay nanocomposites is also discussed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2196–2204, 2004 相似文献
14.
A positive‐working, aqueous‐base‐developable photosensitive polyimide precursor based on poly(amic ester)‐bearing phenolic hydroxyl groups and a diazonaphthoquinone photosensitive compound was developed. The poly(amic ester) was prepared from a direct polymerization of 2,2′‐bis‐(3‐amino‐4‐hydroxyphenyl)hexafluoropropane and bis(n‐butyl)ester of pyromellitic acid in the presence of phenylphosphonic dichloride as an activator. Subsequently, the thermal imidization of the poly(amic ester) precursor at 300°C produced the corresponding polyimide. The inherent viscosity of the precursor polymer was 0.23 dL/g. The cyclized polyimide showed a glass‐transition temperature at 356°C and a 5% weight loss at 474°C in nitrogen. The structures of the precursor polymer and the fully cyclized polymer were characterized by Fourier transform infrared spectroscopy and 1H‐NMR. The photosensitive polyimide precursor containing 25 wt % diazonaphthoquinone photoactive compound showed a sensitivity of 150 mJ/cm2 and a contrast of 1.65 in a 3 μm film with 1.25 wt % tetramethylammonium hydroxide developer. A pattern with a resolution of 10 μm was obtained from this composition. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 352–358, 2002 相似文献
15.
16.
Kang-Yi Lien Chien-Ju Liu Yi-Chien Lin Pao-Lin Kuo Gwo-Bin Lee 《Microfluidics and nanofluidics》2009,6(4):539-555
This study presents a new magnetic bead-based microfluidic platform, which integrates three major modules for rapid leukocytes
purification, genomic DNA (gDNA) extraction and fast analysis of genetic gene. By utilizing microfluidic technologies and
magnetic beads conjugated with CD15/45 antibodies, leukocytes in a human whole blood sample can be first purified and concentrated, followed by extraction of gDNA
utilizing surface-charge switchable, DNA-specific, magnetic beads in the lysis solution. Then, specific genes associated with
genetic diseases can be amplified by an on-chip polymerase chain reaction (PCR) process automatically. The whole pretreatment
process including the leukocytes purification and gDNA extraction can be performed in an automatic fashion with the incorporation
of the built bio-separators consisting of microcoils array within less than 20 min. The detection of single nucleotide polymorphism
(SNP) genotyping of methylenetetra-hydrofolate reductase (MTHFR) C677T region associated with an increased risk of genetic
diseases was further performed to demonstrate the capability of the proposed system. The extracted gDNA can be transported
into a micro PCR chamber for on-chip fast nucleic acid amplification of detection genes with minimum human intervention. Hence,
the developed system may provide a powerful automated platform for pretreatment of human leukocytes, gDNA extraction and fast
analysis of genetic gene. 相似文献
17.
In this paper, we propose a reversible data hiding method for ordered dithered halftone images. To achieve reversibility and high capacity, the proposed method decomposes an ordered dithered halftone into a maximal number of subimage pairs with the same characteristic, and then hides data with a subimage-swapping operation, which converts a subimage pair into a subimage pair with opposite characteristic. Besides, this method maintains good visual quality by exchanging neighboring pixels instead of flipping individual pixels. Experimental results show that this method has the highest capacity among the existing reversible data hiding methods. A reversible authentication watermarking system is also proposed using this reversible watermarking method and it shows better visual quality compared to an existing method. 相似文献
18.
Numerical simulation of detonation using an adaptive Cartesian cut-cell method combined with a cell-merging technique 总被引:1,自引:0,他引:1
A second-order accurate scheme for the Cartesian cut-cell method developed previously by the authors [Ji H, Lien F-S, Yee E. Comput. Methods Appl. Mech. Eng. 198 (2008), 432] is generalized for application to both two- and three-dimensional inviscid compressible flow problems. A cell-merging approach is used to address the so-called “small cell” problem that has plagued Cartesian cut-cell methods. In the present cell-merging approach, the conservative variables are stored at the cut-cell centroid (including the non-merged and merged cut-cells) rather than at the Cartesian cell center. Although this approach results in a more complicated search algorithm for the determination of the neighbor cells (required for the computation of the spatial gradients of the conservative variables), this approach enables the straightforward formulation of a higher than first-order accurate discretization scheme in the vicinity of the (complex and irregular) internal boundaries of the flow domain. Six test cases (including detonation problems) are used to demonstrate the accuracy and capability of the adaptive cut-cell method, for which both mesh refinement and derefinement techniques are employed in the case of an unsteady shock diffraction problem. 相似文献
19.
Because the behavior of HPC at early age may be rather different at late age, this study proposed to establish the strength
models of HPC at different ages, and to explore the difference between these models. A large number of experimental data were
used to compare accuracy of the three model building techniques, nonlinear regression analysis (NLRA), back-propagation networks
(BPN), and genetic operation trees (GOT). The results showed: (1) when NLRA was employed to establish the prediction model,
the approach to establish HPC strength models based on the three separate data sets was more accurate than that used to establish
HPC strength models for the total data set. (2) If an explicit formula is necessary, GOT is the best choice to build concrete
strength models at medium and late ages (i.e., more than 14 days), while NLRA provides greater accuracy at early ages (i.e.,
less than 14 days); otherwise, BPN is the best choice. 相似文献
20.
Facility layout (FL) design presents a particularly interesting area of study because of its relatively high level of attention
to aesthetics and usability qualities, in addition to common engineering objectives such as cost and performance. However,
this generally presents a difficult combinatorial optimization problem for engineers. Swarm intelligence, an approach to decision
making that integrates collective social behavior models such as the bee algorithm (BA) and particle swarm optimization (PSO),
is being increasingly used to resolve various complex optimization problems. In order to integrate BA global search ability
with the local search advantages of PSO, this study proposes a new optimization hybrid swarm algorithm—the particle bee algorithm
(PBA) which imitates the intelligent swarming behavior of honeybees and birds. This study also proposes a neighborhood-windows
technique for improving searching efficiency as well as a self-parameter-updating technique for preventing trapping into a
local optimum in high-dimensional problems. This study compares PBA performance against BA and PSO performance in practical
FL problem. Results show PBA performance is comparable to those of BA and PSO and can be efficiently employed to solve practical
FL problem with high dimensionality. 相似文献