排序方式: 共有106条查询结果,搜索用时 16 毫秒
1.
We report the fabrication and characterization of a magnetically recyclable Fe3O4@Nico@Ag catalyst for reduction reactions in the liquid phase. Fe3O4 is a magnetic core and nicotinic acid was used as the linker for Ag. The characterization was done with X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, vibrating sample magnetometry (VSM), and ultraviolet-visible spectroscopy. VSM measurements proved the super-paramagnetic property of the catalyst. 相似文献
2.
M. Abdulhadi 《Applied Scientific Research》1987,43(4):315-323
A converging nozzle-constant area parallel passage with an outer duct encasing the constant-area passage has been built for investigating the effect of heat transfer on subsonic flow of an air stream. It is concluded experimentally as can be predicted analytically that large quantities of heat are needed in order to accelerate very slow air stream (incompressible) to sonic conditions. It is observed experimentally as confirmed analytically, that the increase in Mach number with heat addition is associated with a decrease in the local static pressure along the axis of the duct. It could be concluded that any more heat added beyond thermal choking will be accompanied by a decrease in the mass flow rate of the compressible flowing air.Nomenclature
A
cross-sectional area of the duct
-
C
P
air
specific heat of air joules/kg. °K
- C
d
discharge coefficient
-
D
duct diameter
-
d
orifice diameter m
-
dA
d
elemental lateral area of the duct
-
h
overall heat transfer coefficient
-
h
head across orifice, mm.
-
M
Mach number
-
m
air
mass flow rate of air
-
P
local static pressure
-
P
b
back pressure at duct outlet
-
P
01
stagnation pressure at duct inlet
-
gas density
-
u
air density upstream of orifice
-
q
incremental heat flow
-
T
local static temperature
-
T
01
stagnation temperature at duct inlet
-
T
h
hot water temperature
-
q
heat added per kg of flowing air
-
V
flow speed 相似文献
3.
Laser array beam propagating through mouse liver tissue is investigated. The turbulence power spectrum of the liver tissue is employed in the extended Huygens–Fresnel method to obtain an optical intensity profile and beam broadening at the observation point in biological liver tissue. Variations of the beam profile and the beam broadening are simulated based on the number of beamlets, source size, wavelength and the ring radius of the array. A biological tissue, illuminated by the laser array beam, exhibits different beam profiles and beam spot radius variations when the number of beamlets, source size, wavelength and the ring radius of the laser array beam are varied. Examining these variations observed in the propagated optical beam and comparing them with the test cases, abnormalities such as cancer and tumor in a biological liver tissue can be diagnosed. 相似文献
4.
M. Ayd?nZ. Durmus H. KavasB. Esat H. SözeriA. Baykal F. Y?lmazM.S. Toprak 《Polyhedron》2011,30(6):1120-1126
Poly(3-thiophene acetic acid)/Fe3O4 nanocomposite is synthesized by the precipitation of Fe3O4 in the presence of poly(3-thiophene acetic acid) (P3TAA). Structural, surface, morphological, thermal properties and conductivity characterization/evaluation of the nanocomposite were performed by XRD, FT-IR, TEM, TGA, and conductivity measurements, respectively. The capping of P3TAA around Fe3O4 nanoparticles was confirmed by FT-IR spectroscopy, the interaction being via bridging oxygens of the carboxylate and the nanoparticle surface through bidentate binding. The crystallite and particle size were obtained as 9 ± 2 nm and 11 ± 1 nm from XRD line profile fitting and TEM image analysis, respectively, which reveal nearly single crystalline nature of Fe3O4 nanoparticles. Magnetization measurements reveal that P3TAA coated magnetite particles do not saturate at higher fields. There is no coercivity and remanence revealing superparamagnetic character. Magnetic particle size calculated from the theoretical fitting as 9.1 nm which coincides the values determined from TEM micrographs and XRD line profile fitting. The comparison to the TEM particle size reveals slightly modified magnetically dead nanoparticle surface. 相似文献
5.
We have presented a method for the fabrication of poly(3-thiophenyl acetic acid) (P3TAA)-BaFe12O19 nanocomposites by the in situ polymerization of P3TAA in the presence of synthesized BaFe12O19 nanoparticles. The nanoparticles and the nanocomposite were analyzed by XRD, FTIR, TGA, TEM, VSM and conductivity techniques for structural and physicochemical characteristics. Crystallographic analysis revealed the phase as hexaferrite and X-ray line profile fitting yielded a crystallite size of 32 nm. The particles, observed by TEM, exhibit irregular shapes and sizes between 100 and 500 nm, revealing polycrystalline character when compared with the crystallite size from XRD. FTIR and TGA analysis results show that P3TAA is conjugated to the particle surface via a carboxylate group and that the composite has a polymer content of ∼10%. Magnetic hysteresis curves do not saturate at high fields, which is a characteristic feature of fine particle systems with grain sizes smaller than 1 μm. Conductivity measurements showed a semiconductor character of the nanocomposite. 相似文献
6.
In strong atmospheric turbulence, the asymptotic on-axis scintillation behaviors of Laguerre Gaussian (LG) beams are examined.
To arrive at the strong-turbulence solution, we utilize the existing filtering approach for weak-turbulence solutions and
our recently reported weak-turbulence scintillation index formula for LG beams. In the limiting case, our solution correctly
predicts the asymptotic strong-turbulence behavior of Gaussian beam wave scintillation. Investigation of the scintillations
versus the propagation distance, source size, wavelength and refractive index structure parameter lead to the conclusion that
the LG beams with higher order radial modes can provide less scintillation. The results are applicable to long-haul atmospheric
optical communication links. 相似文献
7.
Desaktivierung von Pd‐Katalysatoren zur Acetoxylierung: direkte Beobachtung durch XPS‐Untersuchungen
8.
We present a method for the fabrication of PVTri-BaFe12O19 nanocomposites by in-situ polymerization of PVTri in the presence of synthesized BaFe12O19 nanoparticles. Nanoparticles, polymer and nanocomposite were analyzed by XRD, FTIR, TGA, TEM, NMR, GPC and conductivity techniques for structural and physicochemical characteristics. Crystallographic analysis revealed the phase as hexaferrite and X-ray line profile fitting yielded a crystallite size of 17±5 nm. Conjugation of PVTri to nanoparticle surface was assessed to be via carbonyl groups on the polymer. TG analysis revealed that 45 wt% of nanocomposite is inorganic phase (BaFe12O19). It was found out that the ac conductivity of nanocomposite under a certain frequency increases with temperature. 相似文献
9.
Z. Abdulhadi 《Journal of Mathematical Analysis and Applications》2008,338(1):705-709
In this paper, we show the existence of Landau constant for biharmonic mappings of the form F(z)=2|z|G(z)+K(z), |z|<1, where G and K are harmonic. 相似文献
10.
The on-axis scintillation index for a circular dark hollow beam (DHB) propagating in a weak turbulent atmosphere is formulated,
and the scintillation properties of a DHB are investigated in detail. The scintillation index for a DHB reduces to the scintillation
index for a Gaussian beam, an annular beam and a flat-topped beam under certain conditions. It is found that the scintillation
index of a DHB is closely related to the beam parameters and can be lower than that of a Gaussian beam, an annular beam and
a flat-topped beam in a weak turbulent atmosphere at smaller waist sizes and longer propagation lengths.
PACS 42.25.Bs; 42.68.Ay 相似文献