Magnetic properties of Bi-doped Y3Fe5O12 nanoparticles

Haitao Xu,Hua Yang,Wei Xu,Lianxiang Yu 한국물리학회 2008 Current Applied Physics Vol.8 No.1

Bi³+ substituted garnet nanoparticles Y₃. xBiχFe5O₁₂ (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2 and 1.3) were fabricated by a solgel methodand their crystalline structures and magnetic properties were investigated by using X-ray diraction (XRD), IR spectroscopy, thermalgravity analysisdierential thermal analysis (TG-DTA), transmission electron microscope (TEM), Mo¨ssbauer spectroscopy and vibrat-3. xBixFe5O12 have only peaks of the garnet structure.

An experimental study on low-velocity nonlinear flow in vuggy carbonate reservoirs

Haitao Wu,Fujun Li,Jiawen Liu,Jiang Chen,Xiaowei Lv,Wei Hu 한국자원공학회 2016 Geosystem engineering Vol.19 No.4

Vuggy carbonate reservoirs in the Middle East, which have characteristics such as high porosity, low permeability, and few fractures, are significantly different from fractured-vuggy carbonate reservoirs. In this study, single-phase flow experiments and core mercury injection experiments were conducted to analyze the pore size distribution and low-velocity nonlinear flow characteristics of vuggy carbonate rocks in Halfaya oilfield. The results show that the relationship between pseudo-threshold pressure gradient and permeability in matrix carbonate rocks is linear. However, vuggy type does not exhibit the same linear relationship. Compared with matrix type, vuggy carbonate rock has a nonlinear flow zone when the pressure gradient is comparatively low and the nonlinear flow characteristics are quite different from those of low-permeability sandstone reservoirs. Because of the multi-polarization of flow channel radius in vuggy carbonate rocks, fluid stepwise starts flowing as the pressure gradient increases. Vuggy carbonate rock has a pseudo-threshold pressure gradient during the low-velocity flow, but the actual threshold pressure gradient does not exist. The concept of whole channel flow pressure gradient is presented in this paper. The results contribute to improve the understanding of low-velocity flow characteristics of vuggy carbonate reservoirs.

Ripplocations, kink bands and delamination cracks in carbon cathode materials

Wei Wang,Weijie Chen,Haitao Liu,Hongtao Zhang 한국탄소학회 2019 Carbon Letters Vol.29 No.4

A new deformation micromechanism operating in the carbon cathode for aluminum electrolysis termed a ripplocation has been proposed in this paper. The creep deformation of semi-graphitic cathode was measured using a modified Rapoport equipment at 965 °C with cryolite ratio = 4.0. The characteristic of the defect was obtained by analyzing TEM photograph of the carbon cathode with different testing times. The results indicated that basal dislocations, bulk ripplocations, kink bands and delamination cracks appeared in succession in the first two stages of the creep deformation. Ripplocations in the carbon cathode make a layer of carbon atoms to glide relative to each other without damaging the in-plane bonds. Ripplocations could also attract each other and result in kink boundaries. The creep strain of the carbon cathode could be accommodated by kink band and delamination cracks during aluminum electrolysis. A more comprehensive understanding of their micromechanics behaviors is very important and could deeply influence our current knowledge of the deformation mechanism of the carbon cathode for aluminum electrolysis.

ASTROD I, Test of Relativity, Solar-System Measurement and G-Wave Detection

Wei-Tou Ni,Albrecht Rudiger,Etienne Samain,Stephan Schiller,Diana Shaul,Sachie Shiomi,Timothy Sumner,Chien-Jen Tang,Jinhe Tao,Pierre Touboul,Haitao Wang,Andreas Wicht,Ji Wu,Xue-Jun Wu,Yaoheng Xiong,Ch 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.1

ASTROD-I is a mission concept under study to realize the general concept of ASTROD (Astrodynamical Space Test of Relativity using Optical Devices). This mission concept has one spacecraft carrying a payload of a telescope, ve lasers, and a clock together with ground stations (ODSN: Optical Deep Space Network) to test the optical scheme of interferometric and pulse ranging and yet give important scientic results. The scientic goals include a better measurement of the relativistic parameters, a better sensitivity in using optical Doppler tracking method for detecting gravitational waves, and measurement of many solar system parameters more precisely. The weight of this spacecraft is estimated to be about 300-350 kg with a payload of about 100-120 kg. The spacecraft is to be launched with initial period about 290 days and to pass by Venus twice to receive gravity-assistance for achieving shorter periods. With good orbit design, after about 370 days from launch, the spacecraft will arrive at the other side of the Sun for the determination of relativistic parameters.

Novel fuzzy direct torque control based on constructed functional transformed grey model

Zhao, Wei,Li, Zhizhong,Xu, Jiheng,Zhang, Haitao,Yuan, Yuan The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.6

To reduce the ripple of the magnetic flux and torque of motors and the reduce the hysteresis in motor speed control, an improved grey model predictive fuzzy direct torque control (DTC) method based on function transformation is proposed. First, a function transformation is used to transform the sampled sequences to nonnegative values. This overcomes the disadvantages caused by fluctuant and random sampling of the motor torque and stator flux linkage. Second, an equal dimensional new information model is used to keep the dimensions unchanged, which reduces the time to predict the motor parameters through the model. Moreover, the voltage space vector plane is divided into six sectors, which simplifies the fuzzy control system rules. Simulation results show that the proposed fuzzy direct torque control based on the improved grey model method reduces the influence of hysteresis on the control system, decreases the motor flux chain and torque ripple, improves the response speed of the torque and rotational speed, reduces overshoot, achieves good effects in terms of anti-interference capability and dynamic response, and improves the real-time performance and accuracy of the fuzzy control system.

Ripplocations, kink bands and delamination cracks in carbon cathode materials

Wang Wei,Chen Weijie,Liu Haitao,Zhang Hongtao 한국탄소학회 2019 Carbon Letters Vol.29 No.4

A new deformation micromechanism operating in the carbon cathode for aluminum electrolysis termed a ripplocation has been proposed in this paper. The creep deformation of semi-graphitic cathode was measured using a modified Rapoport equipment at 965 °C with cryolite ratio = 4.0. The characteristic of the defect was obtained by analyzing TEM photograph of the carbon cathode with different testing times. The results indicated that basal dislocations, bulk ripplocations, kink bands and delamination cracks appeared in succession in the first two stages of the creep deformation. Ripplocations in the carbon cathode make a layer of carbon atoms to glide relative to each other without damaging the in-plane bonds. Ripplocations could also attract each other and result in kink boundaries. The creep strain of the carbon cathode could be accommodated by kink band and delamination cracks during aluminum electrolysis. A more comprehensive understanding of their micromechanics behaviors is very important and could deeply influence our current knowledge of the deformation mechanism of the carbon cathode for aluminum electrolysis.

High Temperature Plastic Deformation Constitutive Equation of a New Alloy for Piston Ring

Dejin Wei,Ruirui Liu,Chengkun Zuo,Haitao Zhou 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.6

Hot compression tests of a new CrMoV alloy for piston ring are conducted by Gleeble-3800 thermal mechanical simulationtester at the temperature of 950, 1000, 1050, 1100 and 1150 °C and strain rate of 0.01, 0.1, 1, 10 s−1. The results show thatthe true stress strain curves first go up to peak, and then go down to steady state in accord with characteristics of dynamicrecrystallization, indicating that the main softening mechanism of this alloy during hot deformation is dynamic recrystallization. The hot deformation behavior of this alloy is characterized by Arrhenius hyperbolic sine relationship with theactivation energy and stress index. On the basis of the true stress strain curves, the constitutive equation of the peak flowstress of this alloy is established. With the equation, the flow stress of this alloy can be predicated by numerical simulationfor a new type piston ring.

Improved Resistance Switching Characteristics of BiFeO3 Thin Film by Increasing the Annealing Temperature

Zhilei Miao,Wei Wang,Rongchun Yuan,Jun Zhu,Shudong Wu,Haitao Chen,Xianghua Zeng,Qiang Wang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.09

We have fabricated BiFeO3 thin film deposited on Pt/Ti/SiO2/Si substrates by the chemical solution deposition method. The effects of annealing temperature on the thin film structure, resistance switching (RS) properties, conduction mechanisms are investigated. It exhibits improved RS window with high ON/OFF ratio ( ~10 4) for the sample annealed at 650 ℃. XPS characterization indicates that cation ratio of Fe2+/Fe3+ is increased with increasing annealing temperature. Crystal lattice distortion generated by Fe2+ cations, along with oxygen vacancies, commonly contribute to opening the RS window and the increment of conductive filaments. The film's conduction mechanisms under different annealing temperatures are fully discussed. The RS properties of this system can be effectively improved by increasing the annealing temperature, which is crucial prerequisite for future applications of BFO-based thin film device in resistance random access memory.

Configuration Modeling and Experimental Verification with 3D Laser Scanning Technology for a Constrained Elastica Cable

Hongwang Du,Wei Xiong,Haitao Wang,Bin Yuan,Zuwen Wang 보안공학연구지원센터(IJSIP) 2014 International Journal of Signal Processing, Image Vol.7 No.4

Dynamic Island Partition for Distribution System with Renewable Energy to Decrease Customer Interruption Cost

Junpeng Zhu,Wei Gu,Ping Jiang,Shan Song,Haitao Liu,Huishi Liang,Ming Wu 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.6

When a failure occurs in active distribution system, it will be isolated through the action of circuit breakers and sectionalizing switches. As a result, the network might be divided into several connected components, in which distributed generations could supply power for customers. Aimed at decreasing customer interruption cost, this paper proposes a theoretically optimal island partition model for such connected components, and a simplified but more practical model is also derived. The model aims to calculate a dynamic island partition schedule during the failure recovery time period, instead of a static islanding status. Fluctuation and stochastic characteristics of the renewable distributed generations and loads are considered, and the interruption cost functions of the loads are fitted. To solve the optimization model, a heuristic search algorithm based on the hill climbing method is proposed. The effectiveness of the proposed model and algorithm is evaluated by comparing with an existing static island partitioning model and intelligent algorithms, respectively.