Crystallization kinetics and magnetic properties of spinel transition metal ferrite nanoparticles

Yukun Sun,Dongyun Li,Pengzhao Gao,Zhouli Lu,Hongliang Ge 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.5

Spinel transition metal ferrite TMFe2O4 (TM = Co2+, Ni2+, Cu2+, and Zn2+) nanoparticles were prepared via a template-assistedsol-gel method followed by a calcining process, using metal nitrate precursors as raw materials. The prepared specimens werecharacterized using X-ray diffraction (XRD) and a vibrating sample magnetometer (VSM). Their structures, magneticproperties, crystallization kinetics, and the influence of crystal size (D) on the magnetic properties were investigated. It wasfound that the crystal sizes of TMFe2O4 were positively proportional to the calcined temperature and time, and thecrystallization growth activation energy (Ea) increased with the increase of metal ionic radius. The optimum calcinationparameters were obtained to form a crystal closest to the standard crystal. Additionally, the saturation magnetization ofinverse spinel structure specimens was enhanced monotonously and their coercivity showed a potential decrease trend, whilethere was an opposite change trend for normal spinel structure specimens.

Effects of 20-day litter weight on weaned piglets' fighting behavior after group mixing and on heart rate variability in an isolation test

Sun, YaNan,Lian, XinMing,Bo, YuKun,Guo, YuGuang,Yan, PeiShi Asian Australasian Association of Animal Productio 2017 Animal Bioscience Vol.30 No.2

Objective: The objective of this study was to investigate the effect of 20-day litter weight on behavior and heart rate variability (HRV) of piglets under stress. Methods: Forty four original litters were categorized as high litter weight (HW) litters (n = 22) and low litter weight (LW) litters (n = 22) by 20-day litter weight. From each original HW litter, three males and three females were randomly selected after weaning and the 12 piglets from two original litters with similar age of days were regrouped into one new high litter weight (NHW) litter (11 NHW litters in total). The original LW litters were treated with a same program, so that there were 11 new low litter weight (NLW) litters as well. The latencies to first fighting, fighting frequencies and duration within three hours were recorded after regrouping and the lesions on body surface within 48 hours were scored. Besides, HR (heart rate, bpm, beats per minute) and activity count (ACT), time domain indexes and frequency domain indexes of the piglets were measured in an isolation trial to analyze the discrepancy in coping with stress between the original HW and LW litters. Results: The results exhibited that piglets from the HW litters launched fighting sooner and got statistically higher skin lesion score than those from the LW litters (p = 0.03 and 0.02, respectively). Regarding the HRV detection, compared with the HW litters, the LW litters exhibited a lower mean HR (p<0.05). In the isolation test, a highly significant higher ACT value was observed between the HW litters, compared to the LW litters (p<0.01). Significant differences were observed in standard deviation of R-R intervals, standard deviation of all normal to normal intervals, and most frequency-domain indicators: very low-frequency, low-frequency, and high frequency between the HW and LW litters as well. The difference in LF:HF was not significant (p = 0.779). Conclusion: This study suggests that compared with litters of low 20-day litter weights, litters with higher 20-day litter weight take more positive strategies to cope with stress and have stronger HRV regulation capacity; HW litters demonstrate better anti-stress and adaptation capacity in the case of regrouping and isolation.

Kinetic analysis of NO-Char reaction

Shaozeng Sun,Xidong Hu,Penghua Qiu,Juan Qian,Yukun Qin,Juwei Zhang 한국화학공학회 2009 Korean Journal of Chemical Engineering Vol.26 No.2

Two Chinese coals were used to prepare chars in a flat flame flow reactor which can simulate the temperature and gas composition of a real pulverized coal combustion environment. Acid treatment on the YB and SH chars was applied to obtain demineralized chars. Kinetic characterization of NO-char reaction was performed by isothermal thermogravimetry in the temperature range of 973-1,573 K. Presence of catalytic metal matter can increase the reactivity of chars with NO, which indicates that the catalytic effects of inherent mineral matter play a significant role in the NO-char reaction. The discrete random pore model was applied to describe the NO-char reactions and obtain the intrinsic kinetics. The model can predict the data for all the chars at various temperatures well, but underestimate the reaction rates at high carbon conversions for the raw YB and SH chars, which can be attributed to the accumulation of metal catalyst on char surface.

Kinetic modeling of non-hydrocarbon/nitric oxide interactions in a flow reactor above 1,400K

Shaozeng Sun,Zhiqiang Wang,Lin Qian,Yukun Qin,Huali Cao 한국화학공학회 2009 Korean Journal of Chemical Engineering Vol.26 No.3

The reduction of nitric oxide by reaction with non-hydrocarbon fuels under reducing conditions at comparatively higher temperature has been studied with a detailed chemical kinetic model. The reaction mechanism consists of 337 elementary reactions between 65 chemical species based on the newest rate coefficients. The experimental data were adopted from previous work. Analyses by comparing existing experimental data with the modeling predictions of this kinetic mechanism indicate that, at comparatively high temperature, apart from the reaction path NO→ HNO→NH→N2, NO+N→N2 is also prominent. In the presence of CO, NO is partly converted to N by reaction with CO. Based on present model, the reduction of NO at high temperature, which was usually underestimated by previous work, can be improved to some extent.

Mechanism of SO_2 adsorption and desorption on commercial activated coke

Fei Sun,,Jihui Gao,Yuwen Zhu,,Yukun Qin 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.11

We used commercial activated coke (AC) as adsorbent and fixed-bed, FTIR, N_2 adsorption, ion chromatograph as research methods to study the SO2 removal mechanism in the presence of O_2 and H_2O and adsorbate (H_2SO_4)desorption mechanism by combined regeneration. The results showed that AC saturation sulfur retention (52.6 mg/g)in SO_2+O_2+H_2O atmosphere was 4.6 times as much as that (11.4mg/g) in SO_2+O_2 atmosphere and 5.0 times as much as that (10.6 mg/g) in SO_2+O_2 atmosphere at 90 ℃. O-2 and H_2O were necessary in AC desulfurization process. Reaction of SO_3 and H-2O (g) and condensation of sulfuric acid vapor were the dynamic of AC desulfurization process. Water vapor blowing in combined regeneration inhibited the reaction between H_2SO_4 and carbon, and consequently reduced the chemical lost of carbon. AC cumulative quality loss (53.6%) of five-times in C-R was still less than that (62.4%)of three-times in H-R. Water vapor blowing inhibited reactivation effect, as a result reducing the changes of AC pore structure and surface functional groups. Adsorbate H_2SO_4 generated in desulfurization evaporated to sulfuric acid vapor due to the high temperature in regeneration and was carried out by water vapor.

The study of switched reluctance motor for 4-DOF bearingless motor

Ye Yuan,Yukun Sun,Qianwen Xiang,Yuan Ren,Qiang Liu 대한전기학회 2019 Journal of Electrical Engineering & Technology Vol.14 No.1

High integration, low loss and high-reliability are the main development trends of flywheel battery. Thus this study presents the first prototype of a novel high-integration four degrees of freedom (4-DOF) bearingless motor with the advantages of weak coupling and low power consumption. The proposed bearingless motor can realize energy conversion and produce 4-DOF radial forces compared with the conventional bearingless motor for improving the integration of system. A biased flux for producing radial levitation forces is provided by the permanent magnets, which reduce the power consumption of the system. Moreover, a decoupling between the torque and the suspension systems is realized through a structural design, thereby improving the controllability. Structure and winding configurations are introduced and the operation principle of the 4-DOF bearingless motor is discussed. Magnetic circuits analysis and parameter design method are present and a three-dimensional finite element model is established. Electromagnetic characteristics that focus on the high integration, low loss and high reliability are discussed and validated comprehensively. Finally, a favorable controllability of radial suspension forces are verified using finite-element analysis and some experimental results.

계란껍질 분말을 혼입한 시멘트 페이스트의 수화 특성에 관한 실험적 연구

진옥곤 ( Chen Yukun ),순양 ( Sun Yang ),이한승 ( Lee Han-seung ) 한국건축시공학회 2021 한국건축시공학회 학술발표대회 논문집 Vol.21 No.1

The eggshell is a type of bio-waste which is considered hazardous to the environment. In this research, the waste eggshell is utilized as a potential filler in cementitious material. This study has measured by zeta potential to analyze the interaction between the surface of the filler and the calcium ion in the solution. Meanwhile, the effect of eggshell powder on cement hydration process has been determined by isothermal calorimeter. The results show that the surface of eggshell powder have a strong adsorption of Ca2+, and addition of the eggshell powder provides a heterogeneous nucleation site for cement, which promotes the growth of hydration products.

Formation Mechanism of Novel Sidewall Intermetallic Compounds in Micron Level Sn/Ni/Cu Bumps

Siru Ren,Menglong Sun,Zebin Jin,Yukun Guo,Huiqin Ling,Anmin Hu,Ming Li 대한금속·재료학회 2019 ELECTRONIC MATERIALS LETTERS Vol.15 No.5

A new kind of intermetallic compounds (IMC) were found around copper pillar in micron level bumps. To investigate theformation mechanism, three different sized Sn/Ni/Cu bumps (10 μm, 20 μm, 50 μm) were electroplated then reflowed at230 °C for 100 s. After reflow process, a thin layer of IMC was formed around copper pillar, which is attributed to surfacewetting behavior. After aging at 170 °C and 200 °C for different times, the growth mechanism of sidewall IMC was observedby scanning electron microscopy combined with electron backscatter diffraction (EBSD) technology. Surface diffusion wasconsidered to be the main driving force for sidewall IMC growth for the activation energy of them was found to be muchsmaller than that in previous studies. The EBSD results showed a preferred orientation of sidewall Cu3Sngrains <100> beingperpendicular to copper periphery, which indicated direction of Cu atoms flux during Cu3Sngrowth. Formation mechanismof this novel sidewall IMC was proposed based on surface wetting and surface diffusion. The findings contribute to the failuremechanism study in small size bumps and provide insights into the reliability of 3D electronic packaging.

Modeling and Control Design of Dynamic Voltage Restorer in Microgrids Based on a Novel Composite Controller

Huang, Yonghong,Xu, Junjun,Sun, Yukun,Huang, Yuxiang The Korean Institute of Electrical Engineers 2016 Journal of Electrical Engineering & Technology Vol.11 No.6

A Dynamic Voltage Restorer (DVR) model is proposed to eliminate the short-term voltage disturbances that occur in the grid-connected mode, the switching between grid-connected mode and the stand-alone mode of a Microgrid. The proposed DVR structure is based on a conventional cascaded H-bridge multilevel inverter (MLI) topology; a novel composite control strategy is presented, which could ensure the compensation ability of voltage sag by the DVR. Moreover, the compensation to specified order of harmonic is added to implement effects that zero-steady error compensation to harmonic voltage in specified order of the presented control strategy; utilizing wind turbines-batteries units as DC energy storage components in the Microgrid, the operation cost of the DVR is reduced. When the Microgrid operates under stand-alone mode, the DVR can operate on microsource mode, which could ease the power supply from the main grid (distribution network) and consequently be favorable for energy saving and emission reduction. Simulation results validate the robustness and effective of the proposed DVR system.

A Novel Method to Reduce of Cogging Force in a Linear Flux-Switching Permanent Magnet Brushless AC Machine

Gaojun Meng,Ye Yuan,Yukun Sun,Haitao Liu,Zhiying Zhu 대한전기학회 2019 Journal of Electrical Engineering & Technology Vol.14 No.2

The primary linear fl ux-switching permanent magnet (LFSPM) motor has the merits of high speed, high response, and direct drive. However, the presence of the cogging force in LFSPM motors compromises position and speed control accuracy, which can be particularly troublesome at low speeds. A novel approach of suppressing the slot eff ect cogging force for LFSPM is proposed according to repetitive control of time-varying periodic signals. The time-varying periodic thrust disturbance in t-domain is transformed to the signals defi ned in the x-domain, and a repetitive controller is designed. Furthermore, a series of specifi c harmonic currents are added into q-axis reference current, resulting in additional force components to counteract the end eff ect cogging force. Finally, experimental evaluations of the control strategy are performed on an AD5435-controlled LFSPM drive platform. The simulations and experiments verify that the proposed method can suppress the thrust ripple eff ectively.