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排序方式: 共有123条查询结果,搜索用时 19 毫秒
1.
Tania Dr. Sevan D. Houston Lachlan Sharp-Bucknall Tiffany B. Poynder Dr. Mohammad Albayer Prof. Jason L. Dutton 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(68):15863-15866
PhI(OTf)2 has been used for the past 30 years as a strong I(III) oxidant for organic and inorganic transformations. It has been reported to be generated in situ from the reactions of either PhI(OAc)2 or PhI=O with two equivalents of trimethylsilyl trifluoromethanesulfonate (TMS-OTf). In this report it is shown that neither of these reactions generate a solution with spectroscopic data consistent with PhI(OTf)2, with supporting theoretical calculations, and thus this compound should not be invoked as the species acting as the oxidant for transformations that have been associated with its use. 相似文献
2.
Bekzat ABDIKADYR Alp KILI Onur ALEV Serkan BÜYÜKK
SE Zafer Ziya
ZTÜRK 《Turkish Journal of Chemistry》2021,45(2):295
Pristine and WO3 decorated TiO2 nanorods (NRs) were synthesised to investigate n-n-type heterojunction gas sensing properties. TiO2 NRs were fabricated via hydrothermal method on fluorine-doped tin oxide coated glass (FTO) substrates. Then, tungsten was sputtered on the TiO2 NRs and thermally oxidised to obtain WO3 nanoparticles. The heterostructure was characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy. Fabricated sensor devices were exposed to VOCs such as toluene, xylene, acetone and ethanol, and humidity at different operation temperatures. Experimental results demonstrated that the heterostructure has better sensor response toward ethanol at 200 °C. Enhanced sensing properties are attributed to the heterojunction formation by decorating TiO2 NRs with WO3. 相似文献
3.
The behavior of supersonic mixing layers under three conditions has been examined by schlieren photography and laser Doppler velocimetry. In the schlieren photographs, some large-scale, repetitive patterns were observed within the mixing layer; however, these structures do not appear to dominate the mixing layer character under the present flow conditions. It was found that higher levels of secondary freestream turbulence did not increase the peak turbulence intensity observed within the mixing layer, but slightly increased the growth rate. Higher levels of freestream turbulence also reduced the axial distance required for development of the mean velocity. At higher convective Mach numbers, the mixing layer growth rate was found to be smaller than that of an incompressible mixing layer at the same velocity and freestream density ratio. The increase in convective Mach number also caused a decrease in the turbulence intensity (
u/U).List of symbols
a
speed of sound
-
b
total mixing layer thickness between U
1 – 0.1 U and U
2 + 0.1 U
-
f
normalized third moment of u-velocity, f u3/(U)3
-
g
normalized triple product of u2
, g u2/(U)3
-
h
normalized triple product of u
2, h u
2/(U)3
-
l
u
axial distance for similarity in the mean velocity
-
l
u
axial distance for similarity in the turbulence intensity
-
M
Mach number
-
M
c
convective Mach number (for
1 =
2), M
c (U
1 – U
2)/(a
1 + a
2)
-
P
static pressure
-
r
freestream velocity ratio, r U
2/U
1
-
Re
unit Reynolds number, Re U/
-
s
freestream density ratio, s 2/1
-
T
t
total temperature
-
u
instantaneous streamwise velocity
-
u
deviation of u-velocity, uu – U
-
U
local mean streamwise velocity
-
U
1
primary freestream velocity
-
U
2
secondary freestream velocity
-
average of freestream velocities, (U
1 + U
2)/2
-
U
freestream velocity difference, U U
1 – U
2
-
instantaneous transverse velocity
-
v
deviation of -velocity, – V
-
V
local mean transverse velocity
-
x
streamwise coordinate
-
y
transverse coordinate
-
y
0
transverse location of the mixing layer centerline
-
ensemble average
-
ratio of specific heats
-
boundary layer thickness (y-location at 99.5% of free-stream velocity)
-
similarity coordinate, (y – y
0)/b
-
compressible boundary layer momentum thickness
-
viscosity
-
density
-
standard deviation
-
dimensionless velocity, (U – U
2)/U
- 1
primary stream
- 2
secondary stream
A version of this paper was presented at the 11th Symposium on Turbulence, October 17–19, 1988, University of Missouri-Rolla 相似文献
4.
J. J. Baker Khadilah H. M. Al Furaiji O. Tara Liyanage Dr. David J. D. Wilson Dr. Jason L. Dutton Dr. Caleb D. Martin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(6):1581-1587
The reactions of a monomeric borole and a dimeric borole with 2,3-dimethyl-1,3-butadiene and 1,3-cyclohexadiene were investigated. The monomeric borole reacted at ambient temperature whereas heat was required to crack the dimer to form the monomer and induce reactivity. 2,3-Dimethyl-1,3-butadiene reacts to give diverse products resulting from a cycloaddition process with the B−C moiety of the boroles acting as a dienophile, followed by rearrangements to furnish bicyclic species. For 1,3-cyclohexadiene, a [4+2] process is observed in which 1,3-cyclohexadiene serves as the dienophile and the boroles as the diene partner. The experimental results are corroborated with mechanistic theoretical calculations that indicate boroles can serve as either a diene or dienophile in cycloaddition reactions with dienes. 相似文献
5.
The synthesis of crown ethers incorporating tartaric acid units has been systematically examined. The optimum sytheses utilize oligoethylene glycol ditosylates, the bis-dimethylamide of tartaric acid, and sodium hydride as the base. The reaction conditions preserve the chiral centers. 相似文献
6.
Siân E. Dutton Peter D. Battle Florent Tonus 《Journal of solid state chemistry》2008,181(9):2217-2226
Polycrystalline samples of the n=1 Ruddlesden-Popper system Pr3−xSr1+xCrNiO8 have been synthesized over the composition range 0.0<x?1.0 either by the ceramic method or from solution. They have been characterized by an appropriate combination of diffraction methods (X-ray, neutron and electron) and magnetometry (d.c. and a.c.). All compositions having x>0.1 adopt the tetragonal space group I4/mmm; Pr2.9Sr1.1CrNiO8 adopts the orthorhombic space group Fmmm. There is no evidence of Cr/Ni cation ordering in any composition. A maximum in the zero-field cooled magnetic susceptibility is observed at a temperature Tf that decreases with increasing Sr content; 52?Tf (K)?13. The frequency dependence of Tf observed in a.c. susceptibility measurements, together with the analysis of neutron diffraction data, suggests that the atomic magnetic moments in these compositions adopt a spin-glass-like state below Tf. 相似文献
7.
8.
Two common invariants of a graph G are its node clique cover number, θ0(G), and its edge clique cover number, θ1(G). We present in this work a characterization of those graphs for which they and their complements, , have θ0(G)=θ1(G) and θ0()=θ1(). Graphs satis ying these conditions are shown to constitute a subset of those graphs which we term C-graphs. 相似文献
9.
Stahl's concept of k-tuple coloring the nodes of a graph is extended to specify that adjacent nodes must have i colors in common. Complete results for a minimum such coloring are obtained for bipartite graphs and odd cycles. Partial results are shown for complete graphs. 相似文献
10.
Characterization of competition graphs for arbitrary and acyclic directed graphs are presented. 相似文献