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RISS 인기검색어
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- 저자 : Yonghu Chen (검색결과 5 건)
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Performance analysis of two-dimensional DOA estimation for uniform circular array
Chen Liupeng,Mou Weihua,Lv Zhicheng,Zhang Yonghu,Hu Lizhi,Ou Gang 한국통신학회 2023 ICT Express Vol.9 No.5
Perturbation analysis of direction of arrival (DOA) estimation has been studied mostly on one-dimensional arrays rather than planar arrays, which remains room for exploration. For uniform circular arrays with various model errors, we establish the corresponding system model. Then a performance analysis of the two-dimensional MUSIC algorithm is proposed by first-order error analysis and verified by simulation. The results show that the root-mean-squared error of DOA estimation is proportional to the standard deviation of the model errors, including gain-phase errors, sensor position errors, and mutual coupling effect.
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Eu3þ, Liþ doped CaWO4 nanorods: Synthesis, emission-decay curves and effective-refractive index
Xiuna Tian,Guicheng Jiang,Yonghu Chen,Min Yin 한국물리학회 2014 Current Applied Physics Vol.14 No.12
In the present paper, CaWO4: Eu3þ, Liþ nanorods have been successfully synthesized via an oleic acid (OA)-assisted solvethermal route. The transmission electron microscope (TEM) photograph shows that the CaWO4: Eu3þ, Liþ nanorods are monodisperse and uniform nanorods with average diameter of 26 nm. The optical properties of Eu3þ in CaWO4 samples, including photoluminescence (PL) excitation spectra and luminescent decay curves, are investigated in detail. Due to the form of the nanorods, the relative contribution of CTB to the nanorods sample is greater than that to the bulk counterparts. The decay time of the 5D0 level (ranging from 0.94 to 0.65 ms, depending on the filling factor of the nanorods) of the nanorods is longer than that of the bulk counterpart mainly due to the reduction in the size of the nanorods, which introduces an effective-refractive index smaller than the refractive index of CaWO4.
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Temperature dependent luminescence of Dy3þ doped BaYF5 nanoparticles for optical thermometry
Zhongmin Cao,Shaoshuai Zhou,Guicheng Jiang,Yonghu Chen,Changkui Duan,Min Yin 한국물리학회 2014 Current Applied Physics Vol.14 No.8
Dy3þ doped BaYF5 nanoparticles with tetragonal structure were synthesized by hydrothermal method and solvothermal method. The structural and the luminescent properties of the samples were characterized by X-ray diffraction pattern, TEM and photoluminescence spectra. Emission of Dy3þ originated from 4I15/2 located at 450 nm and 4F9/2 located at 478 nm, 573 nm and 660 nm were observed under excitation of 355 nm laser. Behavior of fluorescence intensity ratio with temperature increasing from room temperature to approximately 800 K was investigated. And the optimum temperature range for thermometry is obtained to be 550e800 K according to its sensitivity-temperature relation, indicating the potential application of BaYF5:Dy3þ as a luminescent temperature sensor.
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A new red-emitting phosphor of Eu3+-doped Sr2MgMoxW1−xO6 for solid state lighting
Shuo Li,Xiantao Wei,Kaimo Deng,Xiuna Tian,Yanguang Qin,Yonghu Chen,Min Yin 한국물리학회 2013 Current Applied Physics Vol.13 No.7
The white light-emitting diode has recently attracted great attention as a promising candidate for next generation lighting. The solid solution of Sr1.80Eu0.10Li0.10MgMoxW1-xO6 was synthesized via hightemperature solid-state reaction and this solid solution is treated as a promising red emitting phosphor for white light-emitting diodes. In our cases, the X-ray diffraction, excitation spectra, emission spectra and decay curves of these solid solutions were measured as a function of the Mo/W ratio to characterize the structural and luminescent properties. The excitation bands of the series of phosphors are consistent well with the region of near ultraviolet light, and the phosphors present better color purity than the commercial phosphor Y2O2S:Eu3þ in current use. Taking these properties into consideration,this kind of material may find a great potential application as a red phosphor for near-ultraviolet excited white light-emitting diodes.
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Eu3+-site occupation in CaTiO3 perovskite material at low temperature
Fengfeng Chi,Yanguang Qin,Shaoshuai Zhou,Xiantao Wei,Yonghu Chen,Changkui Duan,Min Yin 한국물리학회 2017 Current Applied Physics Vol.17 No.1
In order to clarify the site occupancy of rare-earth ions in rare-earth doped perovskite materials, the undoped pure CaTiO3 and Eu3þ-doped CaTiO3 samples with a series of Ca/Ti ratio were synthesized via high-temperature solid-state reaction method. X-ray diffraction (XRD) powder patterns confirm that the crystal structure keeps invariant at various Ca/Ti ratios. Measurement results of unit-cell parameters and X-ray photoelectron spectroscopy (XPS) indicate that Eu3þ ions enter into the Ca2þ site. The highresolution photoluminescence spectra of Eu3þ ions at 20 K in all samples did not witness a significant change under the excitation at different wavelength, implying that Eu3þ ions occupy only one type of site. Considering the small spectral splitting range of 5D0/7F2 transition and the large intensity ratio of 5D0 / 7F2/5D0 / 7F1, it can be concluded that Eu3þ occupies Ca2þ site with larger coordinate numbers rather than Ti4þ site.
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