共查询到20条相似文献,搜索用时 31 毫秒
1.
Jeong Ho Ryu Hyong Sik Won Youn-Gon Park Sang Hyun Kim Won Young Song Hideo Suzuki Chulsoo Yoon 《Applied Physics A: Materials Science & Processing》2009,95(3):747-752
Rare-earth-doped oxynitride or nitride compounds have been reported to be photoluminescent and may then serve as new phosphors
because of their good thermal and chemical stabilities. In this work, Eu2+-doped β-SiAlON phosphor with a composition of Eu
x
Si6−z
Al
z
O
z
N8−z
(x=0.018, z=0.23) was prepared by gas-pressured solid state reaction. The crystallinity and particle morphology of the prepared phosphor
were characterized. The Stokes shift and zero-phonon line were calculated mathematically and estimated from the spectral data.
The temperature dependence of photoluminescence was measured from 25 to 250°C. The prepared Eu2+-doped β-SiAlON green phosphor showed superior thermal quenching property compared to silicate (SrBaSiO4:Eu2+) green phosphor. The white light-emitting diode (LED) back-lighting unit (BLU) using the prepared β-SiAlON:Eu2+ green phosphor exhibited higher color gamut than a commercial silicate phosphor. 相似文献
2.
I. A. Starkov A. S. Kozhemyachenko S. F. Bychkov A. P. Nemudry N. Z. Lyakhov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(8):1059-1061
The oxygen permeability of ceramic SrCo0.8 − y
Fe0.2Nb
y
O3 − z
(0 ≤ y ≤ 0.2) and La0.3Sr0.7Co0.6Fe0.2Nb0.2O3 − z
disc membranes as a function of temperature and oxygen partial pressure was studied. Kinetic analysis was performed based
on the experimental data on oxygen permeability as a function of oxygen partial pressure. 相似文献
3.
In the EPR of (La1––x
Gd
y
Ce
x
)Al2 a bottleneck in the relaxation of the conduction electrons to the lattice is present at sufficiently high Gd-concentrations. The bottleneck can be broken by decreasing the Gd-concentration or by adding Cerium as a spin-flip-scatterer.g-factor and line broadening are measured for (La1–y
Gd
y
)Al2 and (La1––x
Gd
y
Ce
x
)Al2 as a function of temperature and Gd- and Ce-concentrations. The Cerium induced relaxationsrate
eL
(Ce) increases linearly with Ce-concentration up tox0.025. This corresponds to the fact, well known by measurements of the Kondo anomalies, that Cerium impurities show no significant interaction up to rather high concentrations. 相似文献
4.
A. B. Kaidalov 《JETP Letters》2003,77(7):349-352
5.
Guo-Yu Lan Yang-Wei Lin Zong-Hong Lin Huan-Tsung Chang 《Journal of nanoparticle research》2010,12(4):1377-1388
This article describes the synthesis of highly water-soluble Zn
x
Hg1−x
Se
y
S1−y
quantum dots (QDs) in aqueous solution through a simple photo-assisted reaction between ZnSe QDs and mercury(I) nitrate dihydrate
[Hg2(NO3)2·2H2O]. In order to deduce the optimal synthesis conditions, we varied several parameters, including the concentrations of mercaptosuccinic
acid (MSA) and Hg2(NO3)2·2H2O, the illumination time, and the reaction temperature. When irradiated at temperatures below 80 °C, the ZnSe QDs reacted
with the S2− ions formed rapidly from MSA and the Hg2+ ions formed from Hg2
2+ ions to form Zn
x
Hg1−x
Se
y
S1−y
QDs through a process of photo-etching and surface combination. Under different conditions, we prepared a series of Zn
x
Hg1−x
Se
y
S1−y
QDs that emit fluorescence at the maximum wavelengths ranging from 405 to 760 nm. Inductively coupled plasma-mass spectrometry
and transmission electron microscopy/energy dispersive spectrometry revealed that the content of Hg in the Zn
x
Hg1−x
Se
y
S1−y
QDs was greater when the synthesis was conducted at higher temperature. The Zn0.88Hg0.12Se0.44S0.56 QDs exhibit improved photostability than crude ZnSe QDs and possess long lifetimes (τ1 ~ 38 ns and τ2 ~ 158 ns). 相似文献
6.
Ying Li Juan Hua Kwei-Chou Yang 《The European Physical Journal C - Particles and Fields》2011,71(10):1775
The implications of the family non-universal Z′ model in the B→K
1(1270,1400)ℓ
+
ℓ
−(ℓ=e ,μ ,τ) decays are explored, where the mass eigenstates K
1(1270, 1400) are the mixtures of 1
P
1 and 3
P
1 states with the mixing angle θ. In this work, considering the Z′ boson and setting the mixing angle θ=(−34±13)○, we analyze the branching ratio, the dilepton invariant mass spectrum, the normalized forward–backward asymmetry and lepton
polarization asymmetries of each decay mode. We find that all observables of B→K
1(1270)μ
+
μ
− are sensitive to the Z′ contribution. Moreover, the observables of B→K
1(1400)μ
+
μ
− have a relatively strong θ-dependence; thus, the Z′ contribution will be buried by the uncertainty of the mixing angle θ. Furthermore, the zero crossing position in the FBA spectrum of B→K
1(1270)μ
+
μ
− at low dilepton mass will move to the positive direction with Z′ contribution. For the tau modes, the effects of Z′ are not remarkable due to the small phase space. These results could be tested in the running LHC-b experiment and Super-B
factory. 相似文献
7.
S. V. Grigoriev V. A. Dyadkin S. V. Maleyev D. Menzel J. Schoenes D. Lamago E. V. Moskvin H. Eckerlebe 《Physics of the Solid State》2010,52(5):907-913
Two systems of noncentrosymmetric cubic helical magnets Mn1 − y
Fe
y
Si (y = 0.06, 0.08, 0.10) and Fe1 − x
Co
x
Si (x = 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.50) have been compared. The concentration dependences of the critical temperature
and magnetic field have been obtained using small-angle polarized-neutron scattering and analyzed in the framework of the
Bak-Jensen model. It has been established that, among the two interactions that play the main role in these systems, i.e.,
the isotropic symmetric ferromagnetic exchange and the Dzyaloshinskii-Moriya isotropic antisymmetric interaction, the former
interaction determines the critical temperature in the Mn1 − y
Fe
y
Si system and the latter interaction determines this temperature in the Fe1 − x
Co
x
Si system. 相似文献
8.
S. Rai Choudhury A. S. Cornell Naveen Gaur 《The European Physical Journal C - Particles and Fields》2008,58(2):251-259
Flavor changing neutral current (FCNC) decays of the B-meson are a very useful tool for studying possible physics scenarios beyond the standard model (SM), where of the many FCNC
modes radiative, purely leptonic and semi-leptonic decays of the B-meson are relatively clean tests. Within this context, the BELLE collaboration has measured the process B→K
*
γ and also searched for the B→K
1(1270)γ process. Theoretical analyses of these processes are yielding similar values of the relevant form factors. In this work we
have used this upper bound in studying the angular correlations for the related semi-leptonic decay mode B
−→K
1−(1270)(→ρ
0
K
−)ℓ
+
ℓ
−, where we have used the form factors that have already been estimated for the B→K
1(1270)γ mode. Note that the additional form factors that are required were calculated using large energy effective theory (LEET). 相似文献
9.
V. S. Rusakov N. I. Chistyakova I. A. Burkovsky A. M. Gapochka T. L. Evstigneeva 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(3):389-393
A M?ssbauer study of the structural and charge states of 57Fe and 119Sn atoms in the compounds of Cu3 −x
Fe
x
SnS4 and Cu2Fe1 − x
Zn
x
SnS4 systems was performed. It was shown that the iron atoms in the compounds of both systems were in the divalent and trivalent
states occupying the tetrahedral positions of the structure. The character of the changes of the degree of covalency of the
Fe2+-S, Fe3+-S and Sn4+-S bonds during the isomorphic substitution in the systems was established. 相似文献
10.
Using form factors derived from the light-cone sum rules, we investigate B
s
→φℓ
+
ℓ
− (ℓ=e,μ,τ) in a single universal extra dimension model (UED). In UED, there is only one new parameter with respect to the Standard
Model (SM), which is the inverse of the compactification radius R of the extra dimension. In this work, the branching ratios, the dilepton invariant mass spectra, the forward–backward asymmetries,
and the lepton polarization asymmetries of B
s
→φℓ
+
ℓ
− are calculated. For a lower value of 1/R, there are some considerable discrepancies between the UED and SM. However, with the increase of 1/R, the effect of UED tends to diminish; in particular for 1/R≥1000 GeV, two models have approximately the same predictions. Compared with data from CDF for B
s
→φμ
+
μ
−, we find that the 1/R tends to be larger than 350 GeV. We also find that the zero crossing point of the forward–backward asymmetry of B
s
→φμ
+
μ
− becomes smaller, which would be an important platform for probing the UED effect. These results could be tested in the Large
Hadron Collider (LHC) at CERN and the future super-B factory. 相似文献
11.
《The European Physical Journal C - Particles and Fields》2009,62(4):625-658
Measurements of the neutral current cross sections for deep inelastic scattering in e
−
p collisions at HERA with a longitudinally polarised electron beam are presented. The single-differential cross-sections d
σ/dQ
2, d
σ/dx and d
σ/dy and the double-differential cross sections in Q
2 and x are measured in the kinematic region y<0.9 and Q
2>185 GeV
2 for both positively and negatively polarised electron beams and for each polarisation state separately. The measurements
are based on an integrated luminosity of 169.9 pb
−1 taken with the ZEUS detector in 2005 and 2006 at a centre-of-mass energy of 318 GeV. The structure functions
and xF
3
γ
Z
are determined by combining the e
−
p results presented in this paper with previously measured e
+
p neutral current data. The asymmetry parameter A
− is used to demonstrate the parity violating effects of electroweak interactions at large spacelike photon virtuality. The
measurements agree well with the predictions of the Standard Model. 相似文献
12.
E. I. Lakhno E. I. Burmakin I. V. Korzun G. Sh. Shekhtman 《Physics of the Solid State》2012,54(3):504-507
The rubidium monoferrite RbFeO2-based solid solutions with the composition Rb2 − 2x
Fe2 − x
P
x
O4 have been synthesized, and their crystal structure and the temperature and concentration dependences of the total and electron
conductivities have been studied. The introduction of P5+ ions has been found to sharply decrease the electron conductivity that prevails in pure rubidium monoferrite and, at the
same time, to increase the ionic conductivity. The latter becomes dominant as the phosphorus concentration increases. The
maximum rubidium-cation conductivity of the materials under study is ∼3 × 10−2 S/cm at 300°C and ∼3 × 10−1 S/cm at 700°C. The results have been compared with the previously obtained data for similar solid solutions based on rubidium
monogallate and monoaluminate. 相似文献
13.
R. Akers G. Alexander J. Allison K. Ametewee K. J. Anderson S. Arcelli S. Asai D. Axen G. Azuelos A. H. Ball et al. 《Zeitschrift fur Physik C Particles and Fields》1995,67(1):45-55
The properties of hadronic Z0 decays with final state photons, measured with OPAL at LEP, have been compared with predictions from two different matrix element calculations ofO(
s
). Two calculations, GNJETS and EEPRAD, have been investigated which use different schemes to restrict the phase space around the poles of the cross section. Assuming the E0-JADE jet definition, both calculations describe the data well in large regions of phase space fory
cut
values around 0.06. For very large and very small jet-photon masses some deviations from the predictions have been found, indicating the importance of higher order corrections. Significant differences between the calculations are only apparent in the predicted rate of 1-jet plus photon events. The rate is higher in GNJETS which reproduces the data better than EEPRAD. 相似文献
14.
D. Buskulic D. Decamp C. Goy J. -P. Lees M. -N. Minard B. Mours B. Pietrzyk R. Alemany F. Ariztizabal P. Comas et al. 《Zeitschrift fur Physik C Particles and Fields》1993,59(2):215-229
Contact interactions are searched for using the differential cross sections for the reactionse
+
e
–e
+
e
–,e
+
e
–µ
+
µ
–,e
+
e
–
+
– ande
+
e
– measured at 12 energies around theZ peak and corresponding to about 20 pb–1 of cumulated luminosity. Four-fermion contact term models assuming various chiralities of lepton currents are fitted to the lepton data and lower limits on the energy scale of such terms are set at 95% c.l. The limits vary in the range 0.9–4.7 TeV, depending on the model and on the lepton flavour. Theee contact terms are searched for assuming various chiralities. Limits on the energy scale between 79 and 130 GeV are extracted from the data. The results are compared and combined with those reported at lower energies.Deceased 相似文献
15.
A. A. Lotin O. A. Novodvorsky V. Ya. Panchenko L. S. Parshina E. V. Khaydukov D. A. Zuev V. V. Rocheva O. D. Khramova K. D. Chtcherbachev 《Physics of the Solid State》2011,53(3):467-471
Thin films of Cd
y
Zn1 − y
O and Mg
x
Zn1 − x
O (y = 0−0.35, x = 0−0.45) ternary alloys have been grown by pulsed laser deposition onto sapphire substrates. The record solubility limits
of Cd (y = 0.3) and Mg (x = 0.35) have been achieved in hexagonal zinc oxide. The mismatch of the lattice parameters a of Cd0.2Zn0.8O and Mg0.35Zn0.65O does not exceed 1%; in this case, the band gap discontinuity is 1.3 eV. The surface roughness of the films does not exceed
2.5 nm at x = 0−0.27 and y = 0−0.20. 相似文献
16.
A. A. Kozlovskii V. F. Khirnyi A. V. Semenov V. M. Puzikov 《Physics of the Solid State》2011,53(4):707-716
The electrical conductivity and Seebeck effect in ceramics based on cobaltites Ho1 − x
Sr
x
CoO3 − δ (x = 0.65, 0.75, 0.85, 0.95) and Er1 − x
Sr
x
CoO3 − δ (x = 0.75, 0.85, 0.95) with a perovskite-like structure have been investigated in the temperature range T > 77 K. All the compounds under study are characterized by the variable-range-hopping conductivity with the temperature dependence
of the electrical resistivity corresponding to the Mott law. It has been found that, in the Ho0.35Sr0.65CoO3 − δ compound, thermally excited Co3+ ions contribute to the electrical conductivity with an increase in temperature to 250 K. The Seebeck coefficient of the systems
studied decreases as the strontium concentration and temperature increase. It has been shown that, for an adequate explanation
of this behavior, proper allowance must be made for the splitting of the 3d levels, as well as for the charge disproportionation of the cobalt ions. 相似文献
17.
A. I. Galyas O. F. Demidenko G. I. Makovetski? K. I. Yanushkevich L. I. Ryabinkina O. B. Romanova 《Physics of the Solid State》2010,52(4):687-690
Regions of the existence of sulfide Gd
x
Mn1 − x
S and selenide Ti
x
Mn1 − x
Se solid solutions have been identified. Their electrical and thermoelectric properties have been studied in the temperature
range 80–900 K. It has been established that the substitution of Gd2+ and Ti2+ ions for Mn2+ cations initiates reversal of the type of charge carrier with respect to the starting compounds MnS and MnSe. The cation
substitution in solid solutions brings about a change from the hole conduction (α > 0) characteristic of the manganese monosulfide
and monoselenide to the electronic conduction (α < 0). 相似文献
18.
19.
Damir Be?irevi? Benjamin Haas 《The European Physical Journal C - Particles and Fields》2011,71(8):1734
The axial coupling and the magnetic moment of D
∗-meson or, more specifically, the couplings gD*Dpg_{D^{\ast}D\pi} and gD*Dgg_{D^{\ast}D\gamma }, encode the non-perturbative QCD effects describing the decays D
∗→Dπ and D
∗→Dγ. We compute these quantities by means of lattice QCD with N
f=2 dynamical quarks, by employing the Wilson (“clover”) action. On our finer lattice (a≈0.065 fm) we obtain gD*Dp+=20±2g_{D^{\ast}D\pi^{+}}=20\pm2, and gD*0 D0g=2.0±0.6 GeV-1g_{D^{\ast0} D^{0}\gamma}=2.0\pm 0.6~{\rm GeV}^{-1}. This is the first determination of gD*0 D0gg_{D^{\ast0} D^{0}\gamma} on the lattice. We also provide a short phenomenological discussion and the comparison of our result with experiment and
with the results quoted in the literature. 相似文献
20.
Jaume Llibre Marco Antonio Teixeira Joan Torregrosa 《Mathematical Physics, Analysis and Geometry》2007,10(3):237-249
The goal of this paper is double. First, we illustrate a method for studying the bifurcation of limit cycles from the continuum
periodic orbits of a k-dimensional isochronous center contained in ℝ
n
with n ⩾ k, when we perturb it in a class of differential systems. The method is based in the averaging theory. Second, we consider a particular polynomial differential
system in the plane having a center and a non-rational first integral. Then we study the bifurcation of limit cycles from
the periodic orbits of this center when we perturb it in the class of all polynomial differential systems of a given degree.
As far as we know this is one of the first examples that this study can be made for a polynomial differential system having
a center and a non-rational first integral.
The first and third authors are partially supported by a MCYT/FEDER grant MTM2005-06098-C01, and by a CIRIT grant number 2005SGR-00550.
The second author is partially supported by a FAPESP–BRAZIL grant 10246-2. The first two authors are also supported by the
joint project CAPES–MECD grant HBP2003-0017. 相似文献