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141.
Chemical effects on the K shell fluorescence yields of Fe, Mn, Co, Cr and Cu compounds were investigated. Samples were excited
using 59.5 keV energy photons from a241 Am radioisotope source. K X-rays emitted by samples were counted by a Si(Li) detector with a resolution 160 eV at 5.9 keV.
Chemical effects on the K shell fluorescence yields (ωk) for Fe, Mn, Co, Cr and Cu compounds were observed. The values are
compared with theoretical, semiempirical fit and experimental ones for the pure elements. 相似文献
142.
本文在双 ̄T2屈服准则的基础上,提出了考虑静水应力影响的广义双T ̄2强度理论,结果表明,广义双T ̄2强度理论与一些材料的实验结果是符合的。 相似文献
143.
Hematoporphyrin IX dimethyl ester (HPDME), tetraphenylporphyrin (TPP), tetra(4-methoxyphenyl)porphyrin (TMPP), tetra(3,4-dimethoxyphenyl)porphyrin
(TDMPP), tetra(3,4,5-trimethoxyphenyl)porphyrin (TTMPP), tetraanthrylporphyrin (TAP) and tetraacridylporphyrin (TACP), and
their Zn2+, SnX
2
2+
, Pd2+ and Pt2+ complexes have been prepared and characterized. The singlet molecular oxygen quantum yield (ϕΔ) values of the above porphyrins and their metal derivatives in N,N-dimethyl formamide (DMF) have been measured in the presence
of 1,3-diphenylisobenzofuran (DPBF) as1O2 acceptor using steady state technique after correcting for the intensity of light absorbed by the photosensitizers. The ϕΔ values for the free base porphyrins are usually around 0.60. Hematoporphyrin IX dimethyl ester and its metal derivatives
follow the order: HPDME (ϕΔ = 0.60) > Zn HPDME (0.40) > PdHPDME (0.34) > Sn(OH)2 HPDME (0.28) > PtHPDME (0.24). Zinc(II) complexes of tetraarylporphyrins show about 65% efficiency in ϕΔ values are compared to the ϕΔ values of their corresponding free base porphyrins. These results can be explained on the basis of catalyzed intersystem
crossing to the ground state. The ϕλ values of the above free base porphyrins and their metal complexes in DMF in presence of DPBF using single-pulsed laser excitation
technique follow similar trends. 相似文献
144.
145.
提高PbWO4晶体光学性能的研究 总被引:3,自引:2,他引:1
钨酸铅(PbWO4)晶体在生长过程中由于缺氧产生了氧空位缺陷和Fe^2+杂质缺陷,使晶体着色,光学性能下降,在晶体生长过程中掺进Sb2O3,能消除氧空位,将Fe^2+氧化为无色的Fe^3+,较大幅度地提高PbWO4晶体的光学性能和闪烁性能。 相似文献
146.
147.
Reactor design and energy concepts for a plasma process of acetylene black production 总被引:1,自引:0,他引:1
Acetylene black can be produced from methane decomposition in a plasma reactor. Different types of plasma reactor are designed for this purpose and a parametric analysis of the system is made. Carbon yield in the reactor seems to be dependent on methane flow rate and plasma power. The results obtained from various types of material analysis of the product obtained show that in some conditions carbon produced under plasma has qualities similar to acetylene black obtained by classical processes. 相似文献
148.
This study is concerned with the mechanics of ductile fracture in bulk metal forming processes by a finite-element analysis and experiments. Developed is a computer program using conventional finite-element method such that the behavior of crack propagation after ductile fracture can be analyzed. The phenomenon of a material separating into two pieces upon shearing and tensile tests has been simulated using the developed computer program. Special attention is focused on the effect of various ductile fracture criteria on crack initiation and propagation during shearing and tensile tests. 相似文献
149.
A. M. Kovrizhnykh V. D. Baryshnikov A. V. Manakov A. F. Nikitenko 《Journal of Applied Mechanics and Technical Physics》2007,48(6):871-877
It is proposed to construct long-term strength and creep relations for metals on the basis of the Coulomb-Mohr criterion.
The creep equations and the long-term strength criterion for plane stress are analyzed in detail. Results of long-term strength
calculations are compared with data of experiments with metallic materials. It is established that theoretical and experimental
results are in satisfactory agreement.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 6, pp. 115–123, November–December, 2007. 相似文献
150.
F. Yang 《Rheologica Acta》1998,37(1):68-72
Based on the perfect slip condition between rigid walls and fluids, the compressive flow of Herschel-Bulkley fluids and biviscous
fluids was studied. The explicit expressions of stresses and fluid velocity were given. To move the rigid walls for a Herschel-Bulkley
fluid with the yield stress (τ0), the mean pressure applied onto the rigid wall should be larger than 2τ0/. No yield surface exists in the interior of the fluids when flow occurs. For a biviscous fluid, a critical load was given.
The fluid behaves like the Bingham fluid when the external applied load onto the wall is larger than the critical load, otherwise
the fluid is Newtonian.
Received: 10 June 1997 Accepted: 22 September 1997 相似文献