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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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Research on fault diagnosis method of reciprocating compressor valve based on IVMD-CMS model
Fengfeng Bie,Suzhen Chen,Fengxia Lyu,Hongfei Zhu,Qianqian Li,Xinting Miao 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.8
As for the complex shock vibration characteristics, the issue of difficult to extract the characteristic information of reciprocating compressor valve, a fault diagnosis method combining informational variational mode decomposition (IVMD) and cyclic modulation spectrum (CMS) is proposed. In this paper, the Bayesian information criterion (BIC) is optimized for the VMD decomposition parameter firstly, and the obtained IVMD algorithm is applied to decompose the signal into intrinsic mode functions (IMFs). Secondly, the signal is reconstructed with the correlation coefficient. Finally, the CMS algorithm is utilized for the reconstructed signal analysis, from which main spectral features of the carrier frequency and cyclic frequency on the cyclic modulation spectrum are obtained. The characteristic information of the signal is highlighted with the amplitude and relationship of the frequency feature. The effectiveness and superiority of the method in the diagnosis of reciprocating compressor valve faults are demonstrated with the numerical simulation and experimental analysis.
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The design and fabrication of 81.25 MHz RFQ for Low Energy Accelerator Facility
Bo Zhao,Shuping Chen,Tieming Zhu,Fengfeng Wang,Xiaofeng Jin,Chenxing Li,Wei Ma,Bin Zhang 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.2
To provide high shunt impendence with low power losses, an 81.25 MHz continuous wave (CW) radiofrequency quadrupole (RFQ) accelerator has been designed and machined as parts of the Low EnergyAccelerator Facility (LEAF). In this paper, the mechanical structure and the main processing technology ofthe RFQ cavities are described according to the physical and geometric parameters requirements of theRFQ. The fabrication of the RFQ has been completed and the test results agree well with the designrequirements. The RFQ accelerator will work in Institute of Modern Physics, Chinese Academy of Sciencesin 2018.
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Yuanyuan Qin,Yifei Wang,Jin Liu,Fengfeng Chen,Aiying Yao,Zhanchun Chen,Fu Junyu 한국고분자학회 2022 Macromolecular Research Vol.30 No.12
The mechanical properties of functionalized graphene/polyethylene (f- GRA/PE) composites and graphene/polyethylene (GRA/PE) composites were studied based on the crystallized models with the molecular dynamics simulation in this paper. The effects of GRA and f-GRA with different mass fractions on the mechanical properties of polyethylene were considered. The results showed that the adsorption capacity of polyethylene molecular chains of f-GRA is stronger, the compatibility of f-GRA/PE system is higher with decreasing the interface distance, and the dynamic property of molecular chain is weaker with reducing the radius of gyration of f-GRA/ PE. Furthermore, the reduction of mechanical energy consumption results in the increase of wear resistance of the system, which is more obvious when the mass fraction of f-GRA increases. Finally, the influence of different tensile rates on the composite system was studied. It was found that during the tensile process, the ability of the composite material to resist deformation in the stretching direction is enhanced, and the functionalized graphene inhibits the movement of the molecular chain due to the adsorption force, which improves the yield stress of the f-GRA/PE composite material, thereby increasing the tensile strength. Tensile rate has a certain effect on mechanical properties, and elastic modulus and yield stress increase with the increase of strain rate.
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