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排序方式: 共有1425条查询结果,搜索用时 31 毫秒
891.
Kang do H Jung HS Ahn N Lee J Seo S Suh KY Kim J Kim K 《Chemical communications (Cambridge, England)》2012,48(43):5313-5315
We rationally designed highly sensitive and selective polydiacetylene (PDA)-phospholipids liposomes for the facile detection of aminoglycosidic antibiotics. The detecting mechanism mimics the cellular membrane interactions between neomycin and phosphatidylinositol-4,5-bisphosphate (PIP(2)) phospholipids. The developed PDA-PIP(2) sensory system showed a detection limit of 61 ppb for neomycin and was very specific to aminoglycosidic antibodies only. 相似文献
892.
L Gao BC Kang GS Hwang do H Ryu 《Angewandte Chemie (International ed. in English)》2012,51(33):8322-8325
Breaking kamp: A catalytic route toward chiral α-alkyl-β-ketoesters using the title reaction of α-alkyl diazoester with aldehydes has been developed. The reaction proceeds with high to excellent enantioselectivities and this methodology was applied to a concise two-step synthesis of the natural pheromone sitophilate. 相似文献
893.
The main objective of this article is to study the effect of discrete heating on free convection heat transfer in a rectangular
porous enclosure containing a heat-generating substance. The left wall of the enclosure has two discrete heat sources and
the right wall is isothermally cooled at a lower temperature. The top and bottom walls, and the unheated portions of the left
wall are adiabatic. The vorticity–stream function formulation of the governing equations is numerically solved using an implicit
finite difference method. The effects of aspect ratio, Darcy number, heat source length, and modified Rayleigh number on the
flow and heat transfer are analyzed. The numerical results reveal that the rate of heat transfer increases as the modified
Rayleigh number and the Darcy number increases, but decreases on increasing the aspect ratio. The average heat transfer rate
is found to be higher at the bottom heater than at the top heater in almost all considered parameter cases except for ε = 0.5. Also, the maximum temperature takes place generally at the top heater except for the case ε = 0.5, where the maximum temperature is found at the bottom heater. Further, the numerical results reveal that the maximum
temperature decreases with the modified Rayleigh number and increases with the aspect ratio. 相似文献
894.
895.
We study a new mixed finite element of lowest order for general quadrilateral grids which gives optimal order error in the H(div)-norm. This new element is designed so that the H(div)-projection Πh satisfies ∇ · Πh = Phdiv. A rigorous optimal order error estimate is carried out by proving a modified version of the Bramble-Hilbert lemma for vector variables. We show that a local H(div)-projection reproducing certain polynomials suffices to yield an optimal L2-error estimate for the velocity and hence our approach also provides an improved error estimate for original Raviart-Thomas element of lowest order. Numerical experiments are presented to verify our theory. 相似文献
896.
Do Yong Kwon 《Acta Mathematica Hungarica》2011,131(3):285-294
Let f(x)=a
d
x
d
+a
d−1
x
d−1+⋅⋅⋅+a
0∈ℝ[x] be a reciprocal polynomial of degree d. We prove that if the coefficient vector (a
d
,a
d−1,…,a
0) or (a
d−1,a
d−2,…,a
1) is close enough, in the l
1-distance, to the constant vector (b,b,…,b)∈ℝ
d+1 or ℝ
d−1, then all of its zeros have moduli 1. 相似文献
897.
We describe a rapid and efficient method for selective deprotection of methoxymethyl (MOM) ethers using ZnBr2 and n-PrSH, which completely removed MOM from diverse MOM ethers of primary, secondary, and tertiary alcohols or phenol derivatives. The deprotection takes less than ten minutes with both high yield and selectivity in the presence of other protecting groups. In addition, the rapid deprotection of MOM ethers of tertiary hydroxyls in high yield with no epimerization allows MOM to be a suitable protecting group for tertiary alcohols. 相似文献
898.
Polypropylene‐low density polyethylene (PP‐LDPE) blends involving PP‐LDPE (90/10 wt%.) with (0.06 wt%) dialkyl peroxide (DAP) and different amounts (5, 10, 20 wt%) of calcium carbonate (CaCO3) were prepared by melt‐blending with a single‐screw extruder. The effect of addition of CaCO3 on thermal decomposition process and kinetic parameters, such as activation energy and pre‐exponential factor of PP‐LDPE blend with DAP matrix, was studied. The kinetics of the thermal degradation of composites was investigated by thermogravimetric analysis in dynamic nitrogen atmosphere at different heating rates. TG curves showed that the thermal decomposition of composites occurred in one weight‐loss stage. The apparent activation energies of thermal decomposition for composites, as determined by the Tang method (TM), the Kissinger–Akahira–Sunose method (KAS), the Flynn–Wall–Ozawa method (FWO), and the Coats–Redfern (CR) method were 156.6, 156.0, 159.8, and 167.7 kJ.mol?1 for the thermal decomposition of composite with 5 wt% CaCO3, 191.5, 190.8, 193.1, and 196.8 kJ.mol?1 for the thermal decomposition of composite with 10 wt% CaCO3, and 206.3, 206.1, 207.5, and 203.8 kJ mol?1 for the thermal decomposition of composite with 20 wt% CaCO3, respectively. The most likely decomposition process for weight‐loss stages of composites with CaCO3 content 5 and 10 wt% was an An sigmoidal type. However, the most likely decomposition process for composite with CaCO3 content 20 wt% was an Rn contracted geometry shape type in terms of the CR and master plots results. It was also found that the thermal stability, activation energy, and thermal decomposition process were changed with the increase in the CaCO3 filler weight in composite structure. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
899.
Seung Jun Lee P. Muralidharan Seung Hwan Jo Do Kyung Kim 《Electrochemistry communications》2010,12(6):808-811
Composite cathodes were synthesized via a citrate combustion method followed by an organic precipitation method. The cathodes were of K2NiF4-type crystal structure with x wt.% Ce0.9Gd0.1O1.95 (CGO)–(100 ? x) wt.% La1.96Sr0.04CuO4 + δ (LSC), where x = 0, 10, 20 and 30. The individual structural phases of the composite cathodes were characterized using a third-generation synchrotron source beamline powder X-ray diffractometer (XRD). The porous grain morphology of the CGO–LSC cathode composite for a symmetrical half-cell was determined from cross-sectional scanning electron microscopy images and elemental line profiles. The composite cathode was made of 20 wt.% CGO–80 wt.% LSC (CL20–80) and was coated onto a Ce0.9Gd0.1O1.95 electrolyte. It showed the lowest area specific resistance (ASR) of 0.07 Ω cm2 at 750 °C. An electrolyte-supported (300 μm thick) single-cell configuration of CL20–80/CGO/Ni-CGO attained a maximum power density of 626 mW cm? 2 at 700 °C. The unique composite composition of CL20–80 demonstrates enhanced electrochemical performance and good chemical compatibility with the CGO electrolyte, as compared with the pure LSC (CL0–100) cathode for IT-SOFCs. 相似文献
900.
An understanding of anomalous capacity of nano-sized CoO anode materials for advanced Li-ion battery
C.H. Chen B.J. Hwang J.S. Do J.H. Weng M. Venkateswarlu M.Y. Cheng R. Santhanam K. Ragavendran J.F. Lee J.M. Chen D.G. Liu 《Electrochemistry communications》2010,12(3):496-498
Nanostructured transition metal oxides are of great interest as a new generation of anode materials for high energy density lithium-ion batteries. In this work, research has been focused on the nano-sized (grain size ~7 nm) CoO anode material and this material delivers charge capacity of 900 mAh g?1 that exceeds the theoretical value of 715 mAh g?1. Possible reason for this unaccounted and unexplained anomalous capacity of the nano-sized CoO material has been suggested by thermogravimetric analysis. A mechanism for this interesting behavior has been systematically evaluated by using X-ray absorption spectroscopy. The anomalous capacity is proposed to be associated with the formation of oxygen-rich CoO material. The results obtained from the nano-sized CoO material have been compared with relatively larger-sized material (grain size ~32 nm). 相似文献