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Xiaoqiang Yu,Lei He,Yuting Hu,Jiajie Li,Xiao Liu,Yuhan Wang,Chunji Li,Munan Yang,Zhenchen Zhong 한국자기학회 2022 Journal of Magnetics Vol.27 No.2
Cerium-containing (Ce) rare earth magnets with extraordinary cost-effectiveness are widely investigated around the world. However, when the concentration of Ce is much more, the kind of these magnets exhibits very poor thermal stability and overall magnetic properties. To weaken these disadvantages, we take eutectic Y50Ce50 co-substitution alloys into account in this work. Magnetic properties, microstructures and metallurgical behaviors of (Y, Ce, Nd)-Fe-B magnets are systematically researched. For (Y50Ce50)10Nd20Fe68.9B1.1 SPSed permanent magnets, good overall magnetic properties are Hcj = 725 kA/m, Jr = 0.73 T and (BH)max = 81 kJ/m³. It schematically depicts that coarse grain zones and fine grain zones occur during the spark plasma sintering (SPS) process. With the Nd content increasing, the deleterious CeFe₂ phases disappear. In addition, the volume fraction and width of coarse grain zones decrease. Ce-rich and Ce-lean regions are also observed in main phases, while Y and Nd elements are uniformly distributed. TEM results show that Nd and Ce are rich in the grain boundary and Y elements prefer to enter in 2:14:1 main phases. This work is favorable to a balanced utilization of high abundance rare earth elements in Nd-Fe-B magnets.
He Jia,Shao Xiaoqiang,Su Qin,Zhao Donglin,Feng Shaojie,오원춘 한국세라믹학회 2023 한국세라믹학회지 Vol.60 No.1
A series of novel cobalt ion-doped ZnCr2−xCoxO4 (x = 0, 0.1, 0.15, 0.2) spinel oxides were synthesized with the hydrothermal method. X-ray diffraction, scanning electron microscope, specific surface area, Raman spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption of oxygen, and other analytical techniques were used to characterize the structure, morphology, and catalytic performance of each sample. Experiment results showed that the doping of cobalt ion significantly promoted the phase crystallization of spinel oxide. Cobalt ion-doped ZnCr2−xCoxO4 (x = 0.1, 0.15, 0.2) nanoparticles with high specific surface area were synthesized at 773 K, with ZnCr2O4 forming a spinel phase at 1173 K. Catalytic experiments revealed that the catalytic activity of ZnCr2−xCoxO4 was effectively improved. Cobalt ion-doped ZnCr1.85Co0.15O4 catalyst catalyzed methane combustion reaction temperature at T90% (the temperature where 90% of methane was converted) of about 573 K, while the undoped ZnCr2O4 sample had the highest catalytic performance at T90% of about 773 K. The order of catalytic activity was: ZnCr1.85Co0.15O4 > ZnCr1.9Co0.1O4 > ZnCr1.8Co0.2O4 > ZnCr2O4. Results of catalytic experiments showed that the surface area of the catalyst increased after partial replacement of chromium ions by cobalt ions and that the increase in surface area of the catalyst provided more active sites, thus improving the reaction activity.
Deyan He,Junshuai Li,Qiang Chen,Xiaoqiang Wang 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
Si thin ¯lms were deposited on Al-coated substrates by inductively coupled plasma chemical vapor deposition with SiH4/H2 mixtures at a low temperature of 350 ±C. The structure of the ¯lms was evaluated by X-ray diraction (XRD), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). XRD spectra indicated that the ¯lms have a highly ordered structure with strong (111) orientation. AFM images showed that the grain size is larger than 150 nm. No residual of Al was detected in the ¯lms by XPS. In view of the high density characteristic of the inductively coupled plasma, a preliminary interpretation was supposed for the mechanism of Al-induced crystallization during low-temperature deposition of Si ¯lm
Thermal management analysis of serial-connection three-chamber piezoelectric pump
Lipeng He,Xiaoqiang Wu,Zheng Zhang,Jingran Wang,Dianbin Hu,Yamei Liu,Guangming Cheng 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.10
The design of a micropump with high performance and excellent reliability on thermal management still remains a challenge for electronic cooling. The performance of a piezoelectric pump with 3 chambers connected in series on thermal management was investigated for electronic cooling in this study. Two S-shaped channel heat sinks and the piezoelectric pump with 3 chambers connected in series were combined to form a loop cooling system. With water as the pumping medium, the tested pump has a flow rate most up to 690.6 ml/min at an input voltage of 220 V and an input frequency of 110 Hz. Suitability of the system has been demonstrated through simulation analysis and experimental verification for temperature control. A temperature reduction of 3 °C of CPU could be achieved at 250 mL/min flow rate generated by the piezoelectric pump with 3 chambers connected in series.
A New Modulation to Eliminate the Impact of Overlap Time for Three-Phase Current Source Converters
Ding Hao,Guo Xiaoqiang,He Meiling,Shi Changli,Jia Dongqiang,Chen Chao,Guerrero Josep M. 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.5
Three-phase current source converter tends to be attractive in future industrial applications. In order to ensure the continuous current for the dc-link inductor of the current source converter (CSC), an overlap time is mandatory for each switch, so as to avoid the over-voltage spike caused by the dc-link inductor current interruption. However, the overlap time results in the undesirable harmonics and current distortion, which fails to comply with the relevant IEEE Standard in terms of power quality. Especially, the negative infl uence caused by overlap time eff ect is much more serious with the increasing of the switching frequency applied to CSC. In order to solve the problem, the impact of the overlap time on the CSC is investigated, and the error resulted from the overlap time is clearly demonstrated. Based on the pulse equivalent principle and the Fourier analysis, the quantitative relationship between the current harmonic and the overlap time is obtained. And then, a new approach to eliminate the impact of overlap time on the CSC is proposed. Finally, the simulation and experimental results are carried out to verify the eff ectiveness of the proposed solution.
B.N. Nhu,Xiaoqiang He,Jialing Li,Ibrahim Rasool Hani,H. Assilzadeh,H. Elhosiny Ali,Samia Elattar 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.30 No.5
Through the examination of literatures, electronic commerce is a subject which is accepted in enterprises to define e-commerce adoption, trends, and issues that are assisting and obstructing its efficacy. E-commerce offers numerous advantages to consumer satisfaction in any place and helps the company to get a competitive benefit over its competitors. The Internet has expanded the scope of business. Many business information is available by the global network that supports information gathering between organizations, businesses and their clients, while various divisions of a business is increasing at anexponential rate. Meanwhile, there are a few barriers to proper e-commerce usage and adoption, such as reliable internet connections, poor e-commerce supporting infrastructures, logistics systems presenting socio-regulatory and poor transportation barriers and demonstrating the significant improvement of e-commerce reliable and affordable Internet provisions, i.e., Internet cost, intensity, and reasonable level of e-readiness. The operational and strategic significance of information-based virtual value chains for all organizations cannot be emphasized. As a consequence, this study confirms worldwide market elements of e-commerce, such as its issues, benefits, relevance, scope, facilitators and projects prospective obstacles in a developing economy.
Yugao Ma,Jiusong Liu,Hongxing Yu,Changqing Tian,Shanfang Huang,Jian Deng,Xiaoming Chai,Yu Liu,Xiaoqiang He 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.6
The solid-state core of a heat pipe cooled reactor operates at high temperatures over 1000 K withthermal and irradiation-induced expansion during burnup. The expansion changes the gap thicknessbetween the solid components and the material properties, and may even cause the gap closure, whichthen significantly influences the thermal and mechanical characteristics of the reactor core. This studydeveloped an irradiation behavior model for HPRTRAN, a heat pipe reactor system analysis code, tointroduce the irradiation effects such as swelling and creep. The megawatt heat pipe reactor MegaPowerwas chosen as an application case. The coupled irradiation-thermal-mechanical model was developed tosimulate the irradiation effects on the heat transfer and stresses of the whole reactor core. The resultsshow that the irradiation deformation effect is significant, with the irradiation-induced strains up to2.82% for fuel and 0.30% for monolith at the end of the reactor lifetime. The peak temperatures during thelifetime are 1027:3 K for the fuel and 956:2 K for monolith. The gap closure enhances the heat transferbut caused high stresses exceeding the yield strength in the monolith
Research on the E-Commerce Credit Scoring Model Using the Gaussian Density Function
( Xiao Qiang ),( He Rui Chun ),( Zhang Wei ) 한국정보처리학회 2015 Journal of information processing systems Vol.11 No.2
At present, it is simple to the electronic commerce credit scoring model, as a brush credit phenomenon in Ecommerce has emerged. This phenomenon affects the judgment of consumers and hinders the rapid development of E-commerce. In this paper, that E-commerce credit evaluation model that uses a Gaussian density function is put forward by density test and the analysis for the anomalies of E-commerce credit rating, it can be fond out the abnormal point in credit scoring, these points were calculated by nonlinear credit scoring algorithm, thus it can effectively improve the current E-commerce credit score, and enhance the accuracy of E-commerce credit score.