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21.
Hicham Mahfoz Kotb Mohamad Mahmoud Ahmad Sajid Ali Ansari Tarek S. Kayed Adil Alshoaibi 《Molecules (Basel, Switzerland)》2022,27(3)
In the current study, we report on the dielectric behavior of colossal-dielectric-constant Na1/2La1/2Cu3Ti4O12 (NLCTO) ceramics prepared by mechanochemical synthesis and spark plasma sintering (SPS) at 850 °C, 900 °C, and 925 °C for 10 min. X-ray powder diffraction analysis showed that all the ceramics have a cubic phase. Scanning electron microscope observations revealed an increase in the average grain size from 175 to 300 nm with an increase in the sintering temperature. SPS NLCTO ceramics showed a room-temperature colossal dielectric constant (>103) and a comparatively high dielectric loss (>0.1) over most of the studied frequency range (1 Hz–40 MHz). Two relaxation peaks were observed in the spectra of the electrical modulus and attributed to the response of grain and grain boundary. According to the Nyquist plots of complex impedance, the SPS NLCTO ceramics have semiconductor grains surrounded by electrically resistive grain boundaries. The colossal dielectric constant of SPS NLCTO ceramics was attributed to the internal barrier layer capacitance (IBLC) effect. The high dielectric loss is thought to be due to the low resistivity of the grain boundary of SPS NLCTO. 相似文献
22.
The Er3+ -Yb3+ codoped in Li2O content tungsten -tellurite (TWL) transparent glasses are synthesized and measured the absorption, Raman and upconversion
luminescence (UPL) spectra. At room temperature intense green emission peak at 560 nm ( 4S3/2→4I15/2) and red emission peak at 670 nm ( 4F9/2→4I15/2) of Er3+ observed even at minimum 86 mW pumping power of infrared 980 nm excitation. For structure of the TWL glass, Raman spectrum
result revealed that an important role of WO3 in the formation of glass network linkage with Li2O. Under this influence estimated lifetime of the 4I11/2 of Er3+ was 1.89 μs and due to lower phonon energy of the glass produce strong upconversion signal. The effect of Er2O3 concentration on emission intensity result indicated that green emission intensity initially increase in compare to red emission.
Under the 980 nm pump power variation measured the relatively increases the red emission to the green emission intensity and
analyze the possible upconversion mechanism and process. 相似文献
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24.
Tashrifi Zahra Mohammadi-Khanaposhtani Mohammad Hamedifar Haleh Larijani Bagher Ansari Samira Mahdavi Mohammad 《Molecular diversity》2020,24(4):1385-1431
Molecular Diversity - 2-Amino-3-cyano-4H-chromenes are structural core motifs that received increasing attention in the last years due to their interesting potential pharmacological properties. In... 相似文献
25.
In this paper we investigate the holographic dark energy scenario in higher derivative gravity with a varying gravitational constant. We introduce a kind of energy density from higher derivative gravity which has role of the same as holographic dark energy. We obtain the exact differential equation , which determine the evolution of the dark energy density based on varying gravitational constant G. We also find out a cosmological application of our work by evaluating a relation for the equation of state of dark energy for low redshifts containing varying G correction. 相似文献
26.
Qamrul Hasan Ansari Siegfried Schaible Jen-Chih Yao 《Journal of Global Optimization》2002,22(1-4):3-16
In this paper, we introduce the system of generalized vector equilibrium problems which includes as special cases the system of generalized implicit vector variational inequality problems, the system of generalized vector variational and variational-like inequality problems and the system of vector equilibrium problems. By using a maximal element theorem, we establish existence results for a solution of these systems. As an application, we derive existence results for a solution of a more general Nash equilibrium problem for vector-valued functions. 相似文献
27.
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29.
L.-C. Ceng S. Al-Homidan Q.H. Ansari J.-C. Yao 《Journal of Computational and Applied Mathematics》2009
In this paper, we propose an iterative scheme for finding a common element of the set of solutions of an equilibrium problem and the set of fixed points of a strict pseudo-contraction mapping in the setting of real Hilbert spaces. We establish some weak and strong convergence theorems of the sequences generated by our proposed scheme. Our results combine the ideas of Marino and Xu’s result [G. Marino, H.K. Xu, Weak and strong convergence theorems for strict pseudo-contractions in Hilbert spaces, J. Math. Anal. Appl. 329 (2007) 336–346], and Takahashi and Takahashi’s result [S. Takahashi, W. Takahashi, Viscosity approximation methods for equilibrium problems and fixed point problems in Hilbert spaces, J. Math. Anal. Appl. 331 (2007) 506–515]. In particular, necessary and sufficient conditions for strong convergence of our iterative scheme are obtained. 相似文献
30.
Saeed Bahadorikhalili Samira Ansari Haleh Hamedifar Leila Ma'mani Mohsen Babaei Rahim Eqra Mohammad Mahdavi 《应用有机金属化学》2019,33(4)
In this paper, a novel catalyst is introduced based on the immobilization of palladium on modified magnetic graphene oxide nanoparticles. The catalyst is characterized by several methods, including transmission electron microscopy, scanning electron microscopy, X‐ray fluorescence, vibrating‐sample magnetometer, Fourier transform‐infrared and dynamic light scattering (DLS) analysis. The activity of the catalyst was investigated in the synthesis of 4(3H)‐quinazolinones via Pd‐catalyzed carbonylation‐cyclization of N‐(2‐bromoaryl) benzimidamides by Mo (CO)6. The Mo (CO)6 is used as a carbon monoxide source for performing the reaction under mild conditions. The catalyst showed good reusability, and no change in activity was observed after 10 cycles of recovery. 相似文献