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Synthesis and characterization of magnetic polymer microspheres with a core-shell structure

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China Particuology 2007年第1期5卷 180-185页

作者： Ming Lu Shu bai kun Yang Yan Sun Department of Biochemical Engineering School of Chemical Engineering and Technology Tianjin University Tianjin 300072 China

Non-porous magnetic polymer microspheres with a core-shell structure were prepared by a novel micro-suspension polymerization technique. A stable iron oxide ferrofluid was used to supply the magnetic core, and the polymeric shell was made of glycidyl methacrylate （GMA monomer） and ethylene dimethacrylate （cross-linker）. In the preparation, polyvinyl alcohol was used as the stabilizer, and a lauryl alcohol mixture as the dispersant. The influence of various conditions such as aqueous phase volume, GMA and initiator amounts, reaction time and stirring speed on the character of the microspheres was investigated. The magnetic microspheres were then characterized briefly. The results indicate that the microspheres with active epoxy groups had a narrow size distribution range from 1 to 10 μm with a volume-weighted mean diameter of 4.5 μm. The saturation magnetization reached 19.9 emu/g with little coercivity and remanence.

关键词： Ferrofluid Micro-suspension polymerization Magnetic microspheres Particle size Magnetization

Induction of the apoptosis of cancer cell by sonodynamic therapy:a review

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Chinese Journal of Cancer Research 2012年第4期24卷 368-373页

作者： Wen-kun bai E Shen Bing Hu Department of Ultrasound In Medicine Shanghai Jiaotong University Affiliated 6th People's HospitalShanghai Institute of Ultrasound in Medicine Department of Ultrasound in Medicine Shandong University Affiliated Qian Fo Shan Hospital

Ultrasound can be used not only in examination, but also in therapy, especially in the therapy of cancer. Sonodynamic therapy is an experimental cancer therapy method which uses ultrasound to enhance the cytotoxic effects of agents known as sonosensitizers. It has been tested in vitro and in vivo. The ultrasound could penetrate the tissue and cell under some of conditions which directly changes cell membrane permeability, thereby allowing the delivery of exogenous molecules into the cells in some degree. Ultrasound could inhibit the proliferation or induce the apoptosis of cancer cells in vitro or in vivo. Recent researches indicated low-frequency and low-intensity ultrasound could induce cell apoptosis, which could be strengthened by sonodynamic sensitivity, microbubbles, chemotherapeutic drugs and so on. Most kinds of ultrasound suppressed the proliferation of cancer cells through inducing the apoptosis of cancer cells. The mechanism of apoptosis is not clear. In this review, we will focus on and discuss the mechanisms of the induction of cancer cell apoptosis by ultrasound.

关键词： Sonodynamic therapy apoptosis cancer mechanism

Design concept development of a variable magnetization motorwith improved efficiency and controllable stiffness for roboticapplications

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Science China(Technological Sciences) 2019年第1期62卷 39-46页

作者： bai kun ZHU Lang YUAN Mi LEE Kok-Meng State Key Lab of Digital Manufacturing Equipment and Technology Huazhong University of Science and Technology Woodruff School of Mechanical Engineering Georgia Institute of Technology

A variable magnetization(VM) motor by incorporating magnets that can be flexibly configured with variable magnetization process is proposed to meet the emerging requirements on motor efficiency and actuator compliance in robotic applications. A generalized spin torque model is established which provides a relationship between the motor torque and two different types of motor inputs, the current inputs and the magnet magnetizations. Avariable magnetization process is proposed based on the study of the hysteresis properties of the magnetic materials and the design criteria for implementing the variable magnetization process with current pulses are established. The feasibility of the variable magnetization is validated with experimental data and the motor functions and performances are numerically demonstrated and evaluated. The results show that the VM motor can maintain high efficiency by switching between two actuation modes. Controllable stiffness at different equilibria can be also achieved with the VM motor with instantaneous magnetizing current pulses.

关键词： compliant actuators direct-drive motors variable stiffness motors variable magnetization motors

Defective layered Mn-based cathode materials with excellent performance via ion exchange for Li-ion batteries

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Journal of Energy Chemistry 2023年第7期82卷 537-546,I0012页

作者： Yongheng Si kun bai Yaxin Wang Han Lu Litong Liu Ziyan Long Yujuan Zhao Beijing Key Laboratory for Green Catalysis and Separation Department of ChemistryThe Faculty of Environment and LifeBeijing University of TechnologyBeijing 100124China

Defective layered Mn-based materials were synthesized by Li/Na ion exchange to improve their electrochemical activity and Coulombic *** annealing temperature of the Na precursors was important to control the P3-P2 phase transition,which directly affected the structure and electrochemical characteristics of the final products obtained by ion *** O3-Li_(0.78)[Li_(0.25)Fe_(0.075)Mn_(0.675)]O_(δ) cathode made from a P3-type precursor calcined at 700℃ was analyzed using X-ray photoelectron spectrometry and electron paramagnetic *** results showed that the presence of abundant trivalent manganese and defects resulted in a discharge capacity of 230 mAh/g with an initial Coulombic efficiency of about 109%.Afterward,galvanostatic intermittent titration was performed to examine the Li^(+) ion diffusion coefficients,which affected the reversible *** principles calculations suggested that the charge redistribution induced by oxygen vacancies(OV_(s))greatly affected the local Mn coordination environment and enhanced the structural ***,the Li-deficient cathode was a perfect match for the pre-lithiation anode,providing a novel approach to improve the initial Coulombic efficiency and activity of Mn-based materials in the commercial application.

关键词： Ion exchange Defective cathode materials Oxygen vacancies Initial coulombic efficiency DFT calculations

Effects of 1 MeV electron radiation on the AlGaN/GaN high electron mobility transistors

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Journal of Semiconductors 2024年第9期45卷 70-75页

作者： Shijie Pan Shiwei Feng Xuan Li Zixuan Feng Xiaozhuang Lu kun bai Yamin Zhang College of Microelectronics Beijing University of TechnologyBeijing 100124China Institute of Microelectronics Chinese Academy of SciencesBeijing 100029China

In this study, the effects of 1 MeV electron radiation on the D-mode GaN-based high electron mobility transistors(HEMTs) were investigated after different radiation doses. The changes in electrical properties of the device were obtained, and the related physical mechanisms were analyzed. It indicated that under the radiation dose of 5 × 10^(14) cm^(-2), the channel current cannot be completely pinched off even if the negative gate voltage was lower than the threshold voltage, and the gate leakage current increased significantly. The emission microscopy and scanning electron microscopy were used to determine the damage location. Besides, the radiation dose was adjusted ranging from 5 × 10^(12) to 1 × 10^(14) cm^(-2), and we noticed that the drain-source current increased and the threshold voltage presented slightly negative shift. By calculations, it suggested that the carrier density and electron mobility gradually increased. It provided a reference for the development of device radiation reinforcement technology.

关键词： AlGaN/GaN HEMT electron radiation performance degradation device damage

Sliding tribological characteristics of Ti48Zr20Nb12Cu5Be15 metallic glass matrix composites under different conditions

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Journal of Iron and Steel Research International 2018年第3期25卷 282-290页

作者： Zhong-kun bai Li-ming Du Ming Chen Min Zhang Xiao-hui Shi Hui-jun Yang College of Materials Science and Engineering TaiyuanUniversity of Technology Taiyuan 030024 Shanxi China

A systematic research on the tribological characteristics of Ti48Zr20Nb12Cu5Be15 metallic glass matrix composites was performed under different normal loads in dry condition and simulated seawater. The wear rate decreased with the increase in normal load under dry and simulated seawater conditions. The friction coefficient was lower in the dry condition than in the simulated seawater. The composite showed better wear resistance at lower loads （3, 5 and 10 N） hut poor wear resistance at higher loads （15 and 17 N） in the simulated seawater. The analysis of the worn surface illustrated that the wear mechanism in dry condition was plastic deformation, adhesive wear and abrasive wear at 3 and 5 N, while it was abrasive wear and adhesive wear at 10, 15 and 17 N. The wear mechanism in simulated seawater was abrasive wear, plastic deformation and adhesive wear at 3 N, adhesive wear at 10 N, and abrasive wear at 5, 15 and 17 N. At the same time, the corrosion occurred during wear tests in the simulated seawater.

关键词： Amorphous material Rapid solidification Friction Wear Corrosion

Coating Multi-walled Carbon Nanotubes with Uniform Silica Shells:Independent of Surface Chemistry

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Chemical Research in Chinese Universities 2011年第2期27卷 181-184页

作者： LI Ling DENG Xlao-yong bai Ming-kun WU Ming-hong LIU Yuan-fang Institute of Nanochemistry and Nanobiology School of Environmental and Chemical Engineering Shanghai University Shanghai 200444 P. R. China Beijing National Laboratory for Molecular Sciences Department of Chemical Biology College of Chemistry and Molecular Engineering Peking University Beo＇ing 100871 P. R. China

A facile and general method was described to coat six types of multi-walled carbon nanotubes, functionalized by either noncovalent or covalent way, with smooth silica shells. 3-Aminopropyltriethoxysilane（APTES） and pH value play important roles in the coating process and the thickness of silica shell could be controlled by the added amount of silicon alkoxides. After the removal of multi-walled carbon nanotubes by calcination, the silica nanotubes were successfully prepared.

关键词： Carbon nanotube Silica Core-shell structure

Hydrodynamic characteristics of a typical karst spring system based on time series analysis in northern China

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China Geology 2021年第3期4卷 433-445页

作者： Yi Guo Feng Wang Da-jun Qin Zhan-feng Zhao Fu-ping Gan bai-kun Yan Juan bai Haji Muhammed China Aero Geophysical Survey and Remote Sensing Center for Natural Resources China Geological SurveyBeijing 100083China Chinese Academy of Environmental Planning Beijing 100012China Key Laboratory of Shale Gas and Geoengineering Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China Key Laboratory of Water Cycle and Related Land Surface Processes Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China School of Applied Natural Science Adama Science and Technology UniversityP.O.Box 1888AdamaEthiopia

In order to study the hydrodynamic characteristics of the karst aquifers in northern China,time series analyses(correlation and spectral analysis in addition with hydrograph recession analysis)are applied on Baotu Spring and Heihu Spring in Jinan karst spring system,a typical karst spring system in northern *** show that the auto-correlation coefficient of spring water level reaches the value of 0.2 after 123 days and 117 days for Baotu Spring and Heihu Spring,*** regulation time obtained from the simple spectral density function in the same period is 187 days and 175 days for Baotu Spring and Heihu *** auto-correlation coefficient of spring water level reaches the value of 0.2 in 34-82 days,and regulation time ranges among 40-59 days for every single hydrological *** delay time between precipitation and spring water level obtained from cross correlation function is around 56 days for the period of 2012-2019,and varies among 30-79 days for every single hydrological *** addition,the spectral bands in cross amplitude functions and gain functions are small with 0.02,and the values in the coherence functions are *** these behaviors illustrate that Jinan karst spring system has a strong memory effect,large storage capacity,noticeable regulation effect,and time series analysis is a useful tool for studying the hydrodynamic characteristics of karst spring system in northern China.

关键词： Karst spring Karst aquifer Hydrodynamic Time series analysis Correlation analysis Spectral analysis Hydrogeological survey engineering Jinan Shandong Province China

Boosting triplet self-trapped exciton emission in Te(IV)-doped Cs_(2)SnCl_(6) perovskite variants

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Nano Research 2021年第5期14卷 1551-1558页

作者： Ruosheng Zeng kun bai Qilin Wei Tong Chang Jun Yan Bao Ke Jialuo Huang Liushun Wang Weichang Zhou Sheng Cao Jialong Zhao Bingsuo Zou School of Physical Science and Technology MOE Key Laboratory of New Processing Technology for Non-ferrous Metals and MaterialsGuangxi Key Laboratory of Processing for Non-ferrous Metals and Featured MaterialsGuangxi UniversityNanning530004China School of Materials Science and Engineering Guilin University of Electronic TechnologyGuilin541004China School of Physics and Electronics Key Laboratory of Low-dimensional Quantum Structures and Quantum Control of Ministry of EducationKey Laboratory for Matter Microstructure and Function of Hunan ProvinceSynergetic Innovation Center for Quantum Effects and ApplicationHunan Normal UniversityChangsha410081China

Perovskite variants have attracted wide interest because of the lead-free nature and strong self-trapped exciton (STE) emission. Divalent Sn(II) in CsSnX3 perovskites is easily oxidized to tetravalent Sn(IV), and the resulted Cs2SnCl6 vacancy-ordered perovskite variant exhibits poor photoluminescence property although it has a direct band gap. Controllable doping is an effective strategy to regulate the optical properties of Cs2SnX6. Herein, combining the first principles calculation and spectral analysis, we attempted to understand the luminescence mechanism of Te4+-doped Cs2SnCl6 lead-free perovskite variants. The chemical potential and defect formation energy are calculated to confirm theoretically the feasible substitutability of tetravalent Te4+ ions in Cs2SnCl6 lattices for the Sn-site. Through analysis of the absorption, emission/excitation, and time-resolved photoluminescence (PL) spectroscopy, the intense green-yellow emission in Te4+:Cs2SnCl6 was considered to originate from the triplet Te(IV) ion 3P1→1S0 STE recombination. Temperature-dependent PL spectra demonstrated the strong electron-phonon coupling that inducing an evident lattice distortion to produce STEs. We further calculated the electronic band structure and molecular orbital levels to reveal the underlying photophysical process. These results will shed light on the doping modulated luminescence properties in stable lead-free Cs2MX6 vacancy-ordered perovskite variants and be helpful to understand the optical properties and physical processes of doped perovskite variants.

关键词： Cs_(2)SnCl_(6)perovskite variants equivalent ion doping self-trapped exciton(STE)emission electron-phonon coupling first principles calculation