53 results on '"Chengzhi Li"'
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2. Surface engineered environment-stable red-emitting fluorides for white light emitting diodes
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Wenli Zhou, Jing Yang, Peilan Luo, Chengzhi Li, Jilin Zhang, Zhongxian Qiu, Menglin Ye, Pingping Wan, and Shixun Lian
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Photoluminescence ,Materials science ,Process Chemistry and Technology ,Analytical chemistry ,Phosphor ,Surface engineering ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,chemistry ,Resist ,Materials Chemistry ,Ceramics and Composites ,Quantum efficiency ,Luminous efficacy ,Fluoride ,Diode - Abstract
Poor water stability is the main problem of commercialized Mn4+-doped fluorides for white light emitting diode (WLED) application. This work proposes a surface engineering strategy to rebuild a Mn4+-free fluoride shell on fluorides to effectively resist the destruction from water molecules. By simple processing using glyoxylic acid (GA) solution, the moisture resistance of the red-emitting fluorides can be significantly improved. The photoluminescence (PL) quantum efficiency (QE) of the surface-engineered K2SiF6:Mn4+ (KSFM-GA) still maintain 98.43% after water immersion for 360 h, in sharp contrary to the untreated one (its PLQE decreases to 59.79%). Additionally, PL intensity of the hydrolysed KSFM can be recovered to 99.1% through the treatment of the reducing GA solution. By using the high-stability KSFM-GA red phosphor, the as-fabricated high-performance warm-WLED device can still maintain 84.6% in luminous efficacy, higher than that (79.6%) with the untreated KSFM, after 500 hours of aging in a high temperature (85 oC) and high humidity (85%) environment. more...
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- 2022
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Catalog
3. The period function of reversible Lotka-Volterra quadratic centers
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Changjian Liu, Chengzhi Li, Dechen Wang, and Jinming Li
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Work (thermodynamics) ,Class (set theory) ,Monotone polygon ,Quadratic equation ,Applied Mathematics ,Computation ,Applied mathematics ,Monotonic function ,Function (mathematics) ,Analysis ,Mathematics ,Exponential function - Abstract
In this paper it is proved that the period function of reversible Lotka-Volterra quadratic systems is monotone, unless the associated center is isochronous. For this class of quadratic systems, the traditional criterion function on the monotonicity of period function does not work, we improve the criterion function to new different forms such that it can be used for different values of the parameters in the system. Furthermore, to overcome the difficulty that the exponential function of the parameter appears in the first integral, in our study we combine the analytic expressions with their geometric meanings and symbolic computations. These methods may be used for other problems. more...
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- 2022
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4. A Multitask Deep Learning Radiomics Model For Predicting The Macrotrabecular-Massive Subtype and Prognosis of Hepatocellular Carcinoma after Hepatic Arterial Infusion Chemotherapy
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Xuelei He, Kai Li, Ran Wei, Mengxuan Zuo, Wang Yao, Zechen Zheng, Xiaowei He, Yan Fu, Chengzhi Li, Chao An, and Wendao Liu
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- 2023
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5. Therapeutic Effects of Low-Intensity Pulsed Ultrasound on Premature Ovarian Insufficiency
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Yao Liu, Chengzhi Li, Yijin Fan, and Huajun Tang
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0301 basic medicine ,Acoustics and Ultrasonics ,Ultrasonic Therapy ,Biophysics ,Uterus ,Physiology ,Primary Ovarian Insufficiency ,Low-intensity pulsed ultrasound ,Premature ovarian insufficiency ,Rats, Sprague-Dawley ,Random Allocation ,03 medical and health sciences ,0302 clinical medicine ,medicine ,Animals ,Radiology, Nuclear Medicine and imaging ,Estrous cycle ,030219 obstetrics & reproductive medicine ,Radiological and Ultrasound Technology ,business.industry ,Therapeutic effect ,Ultrasound ,medicine.disease ,Rats ,Premature ovarian failure ,Pregnancy rate ,Treatment Outcome ,030104 developmental biology ,medicine.anatomical_structure ,Female ,business - Abstract
We explored the therapeutic effects of low-intensity pulsed ultrasound (LIPUS) on a rat model of ovarian damage induced by cyclophosphamide. A total of 44 female rats with premature ovarian insufficiency induced by cyclophosphamide were randomly divided into two groups (an ultrasound group and a control group); 22 normal rats without premature ovarian insufficiency were also included as a third group. The ultrasound group was treated with LIPUS, while the other two groups received the same treatment but without any power output. We monitored the estrous cycles of all rats. Seven days after treatment, 21 rats were selected to mate with male rats. We then recorded the pregnancy rate along with the number and weight of newborn rats per nest. We collected samples of blood, uterus and ovaries from the remaining 45 rats before they were sacrificed. Compared with the normal group, the control group exhibited disordered estrous cycles, more atretic follicles (p 0.05). In conclusion, our data indicate that LIPUS could improve some ovarian functions of rats with premature ovarian insufficiency. more...
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- 2021
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6. Luminescence tuning of Tb/Eu Co-doped zinc aluminoborosilicate glasses for white LED applications
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Chengzhi Li, Zhongxian Qiu, Xingxing Zheng, Shixun Lian, Mao-lin Yang, Ping Wang, Wenli Zhou, Guanhua Wang, Jilin Zhang, and Liping Yu
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010302 applied physics ,Materials science ,Process Chemistry and Technology ,Analytical chemistry ,Infrared spectroscopy ,chemistry.chemical_element ,Phosphor ,02 engineering and technology ,Zinc ,021001 nanoscience & nanotechnology ,01 natural sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,chemistry ,law ,0103 physical sciences ,Activator (phosphor) ,Materials Chemistry ,Ceramics and Composites ,Calcination ,Thermal stability ,Emission spectrum ,0210 nano-technology ,Luminescence - Abstract
Tb3+/Eu2+,3+-doped zinc aluminoborosilicate glasses were prepared using a conventional high temperature melt-quenching method. Infrared spectra and physical properties of as-prepared glasses verified that the addition of Tb/Eu causes structural weakness in the glass. Tuning of blue, green, and red emission bands achieves white light for the zinc aluminoborosilicate glasses. The broad blue emission band is attributed to the 5d-4f transition of Eu2+ due to partial reduction of Eu3+ during calcination in ambient atmosphere. The reduction of Eu3+ is related to the formation of Eu Zn • and V Zn '' defects and host alkalinity decreases with the addition of Eu3+. Emission spectra and decay curves confirm energy transfer from Tb3+ to Eu3+ in the zinc aluminoborosilicate glasses, and relative intensities of green and red luminescence can be tuned through concentrations changes of Tb3+ and Eu2+,3+. When the concentrations of Tb3+ and Eu2+,3+ are equal to 6% and 1.2%, respectively, a neutral white light emitting glass is obtained. Furthermore, the white-emitting glass shows very high thermal stability compared to a commercial Y3Al5O12:Ce3+ phosphor. Therefore, luminescence tuning of glasses through changing activator concentrations and energy transfer is expected to achieve high-powered white LEDs. more...
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- 2020
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7. Validity of isothermal kinetic prediction by advanced isoconversional method
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Kui Li, Chang Gan, Wei Zhang, Chengzhi Li, and Guangqiang Li
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General Physics and Astronomy ,Physical and Theoretical Chemistry - Published
- 2023
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8. DEM study on size segregation and voidage distribution in green bed formed on iron ore sinter strand
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Chengzhi Li, Damien O’Dea, Roberto Moreno-Atanasio, and Tom Honeyands
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geography ,Materials science ,geography.geographical_feature_category ,General Chemical Engineering ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,Discrete element method ,Rill ,Distribution (mathematics) ,020401 chemical engineering ,Iron ore ,Permeability (electromagnetism) ,engineering ,0204 chemical engineering ,Composite material ,0210 nano-technology ,Granule (geology) - Abstract
The size segregation and voidage distribution down a green bed formed on an iron ore sinter strand were investigated experimentally and using Discrete Element Method (DEM). The simulated and experimental results showed that an increase in feed rate (from 6 kg/s/m to 18 kg/s/m) significantly decreased the level of vertical size segregation and the granule packing voidage of each bed sub-layer. With the increase in rill plate angle (from 45° to 65°), the level of vertical size segregation first decreased and, then, remained relatively constant. Furthermore, the results indicated that the voidage of each bed sub-layer generally increased with the increase in λ. In conclusion, enhancing the vertical size segregation down the green bed can generally improve the voidage of the green bed and thus increase the bed permeability. more...
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- 2019
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9. Material, energy and exergy flows of the oxygen blast furnace process with sintering flue gas injection
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Jingqi Li, Chengzhi Li, Wei Zhang, Juhua Zhang, and Zhengliang Xue
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Renewable Energy, Sustainability and the Environment ,Strategy and Management ,Building and Construction ,Industrial and Manufacturing Engineering ,General Environmental Science - Published
- 2022
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10. Citri Reticulatae Pericarpium (Chenpi): A multi-efficacy pericarp in treating cardiovascular diseases
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Jiami Zou, Jiaojiao Wang, Weile Ye, Jing Lu, Chengzhi Li, Dongmei Zhang, Wencai Ye, Suowen Xu, Chunbo Chen, Peiqing Liu, and Zhiping Liu
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Pharmacology ,Citrus ,Plants, Medicinal ,Cardiovascular Diseases ,Humans ,General Medicine ,Drugs, Chinese Herbal - Abstract
Citri Reticulatae Pericarpium (CRP) has been utilized as a versatile medicinal herb with wide cardiovascular benefits in Asian nations for centuries. Accumulating evidence suggests that CRP and its components are effective in preventing cardiovascular diseases (CVDs) such as atherosclerosis, myocardial infarction, myocardial ischemia, arrhythmia, cardiac hypertrophy, heart failure, and hypertension. Studies show that the two most bioactive components of CRP are flavonoids and volatile oils. The cardiovascular protective effects of CRP have attracted considerable research interest due to its hypolipidemic, antiplatelet activity, antioxidant and anti-inflammatory effects. Hereby, we provide a rigorous and up-to-date overview of the cardiovascular protective properties and the potential molecular targets of CRP, and finally highlight the pharmacokinetics and the therapeutic potential of the main pharmacologically active components of CRP to treat CVDs. more...
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- 2022
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11. The Decision-Making Process of China's Human Spaceflight Program
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Chengzhi Li, Bingtao Ma, and Xiang Li
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Economics and Econometrics ,Sociology and Political Science ,Space and Planetary Science ,Law - Published
- 2022
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12. Numerical study of the dynamic behaviour of iron ore particles during wet granulation process using discrete element method
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Xianju Shi, Chengzhi Li, Qiang Wang, Guangqiang Li, Wei Zhang, and Zhengliang Xue
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General Chemical Engineering - Published
- 2022
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13. Flexible graphene oxide/poly(ethylene glycol) composite films for lubrication application
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Feng Hu, Jianhui Li, Lisha Wang, Hailin Lu, Guangshen Xu, and Chengzhi Li
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Materials science ,Graphene ,Composite number ,Oxide ,Polyethylene glycol ,engineering.material ,Condensed Matter Physics ,law.invention ,chemistry.chemical_compound ,Coating ,chemistry ,law ,PEG ratio ,Lubrication ,engineering ,General Materials Science ,Thermal stability ,Composite material - Abstract
For the rotating parts of low-speed heavy machinery, it is difficult to replace and add lubricants, so coating the mechanical surface is an effective method to reduce friction and wear. In this study, a smooth functional film with good mechanical strength was designed and prepared by combining graphene oxide (GO) with polyethylene glycol (PEG). This wachieved by grafting PEG onto the GO surface. The effects of lubrication for the cases of flexible lubricating film, no film, and single film were analysed. The lubrication characteristics of GO–PEG flexible composite film under water lubrication, are discussed in detail. The results show that the mixture of PEG and GO can significantly improve the thermal stability, film forming properties and mechanical properties of GO–PEG composites. The membrane has a good friction limit performance. Compared with the uncoated surface, the friction coefficient is reduced by 74% and the wear rate is reduced by 70%. more...
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- 2022
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14. Fine controllable blue emission and its mechanism in Ce3+-doped orthosilicate solid solution phosphors for different plant growths
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Yaru Yang, Chengzhi Li, Shixun Lian, Yiting Lin, Zhongxian Qiu, Yue Han, Liping Yu, Jilin Zhang, and Wenli Zhou
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Materials science ,Doping ,Analytical chemistry ,Phosphor ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,law.invention ,chemistry.chemical_compound ,chemistry ,Geochemistry and Petrology ,law ,Excited state ,Orthosilicate ,0210 nano-technology ,Luminescence ,Solid solution ,Monoclinic crystal system ,Light-emitting diode - Abstract
The designed Ce3+-doped alkaline-earth silicate phosphors CamSr2–m–nBanSiO4:Ce3+,Li+ (CSBS:Ce3+) were synthesized by a high temperature solid-state reaction. The crystal field splitting and the centroid shift from the free ion energy of 5d configuration were approximated from the spectrum for Ca2SiO4, Sr2SiO4 and Ba2SiO4 phosphors. The single-phase purity was checked by means of X-ray diffraction. Here, when the doped concentration of Ca2+ is less than 80% (m ≤ 1.6), we report the structural phase transformation from monoclinic system β-Ca2SiO4 to orthorhombic system α׳-Ca2SiO4. The phosphors excited by near-ultraviolet (NUV) light at wavelengths ranging from 200 to 400 nm demonstrate a broad asymmetric blue emission band. The emission peak wavelength redshifts firstly from 417 nm of Ca2SiO4 to 438 nm of Sr0.3Ca1.6SiO4, and then blueshifts to 411 nm of Sr2SiO4, and the end of 401 nm of Ba2SiO4. These results indicate that the tunable blue-emission of the phosphors can be realized through changing the solid solution components, which has a potential use as a blue component for fabricated precision modulation LEDs light sources and auxiliaries of SSC plastics films for different plant growths. We discuss in detail the possible mechanism and energy diagram of the tunable blue luminescence in CamSr2–m–nBanSiO4:Ce3+,Li+ phosphors. more...
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- 2018
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15. To tune europium valence by controlling the composition in diphase silicate phosphors
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Yiting Lin, Zhongxian Qiu, Shixun Lian, Liping Yu, Chengzhi Li, Wenli Zhou, Jukui Zhou, and Jilin Zhang
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Materials science ,Valence (chemistry) ,Photoluminescence ,Analytical chemistry ,chemistry.chemical_element ,Phosphor ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Crystallinity ,chemistry ,Geochemistry and Petrology ,Impurity ,0210 nano-technology ,Europium ,Luminescence ,Monoclinic crystal system - Abstract
Commercial phosphors always require fewer impurities and higher crystallinity, but sometimes it is difficult or strict to synthesize a pure phase compound. Indeed, if the practical application is not influenced, it is acceptable to synthesize a kind of phosphors with diphase matrix that have similar structure and photoluminescence properties. In present work, we designed and synthesized a series of (1–x)BaMSiO4·xBa2MSi2O7:Eu (M = Zn2+, Mg2+) diphase phosphors which contained two phases BaMSiO4 (hexagonal, P63) and Ba2MSi2O7 (monoclinic, C2/c) by a high temperature solid-state reaction in air condition. The structures and luminescence properties related to the phase transform from BaMSiO4 to Ba2MSi2O7 were analyzed carefully. The results show that the self-reduction ability of Eu3+ is not the best in above four compounds, respectively. But it reaches the maximum and gets the green emission under the UV lamp when the matrix is in a proper ratio of two phases, which suggests that the heterostructure between the two crystals (BaMSiO4 and Ba2MSi2O7) improves the self-reduction process of the diphase. The possible mechanism of the tunable europium valence and the luminescent properties in (1–x)BaMSiO4·xBa2MSi2O7:Eu phosphors were discussed in detail. more...
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- 2018
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16. Highly efficient solar evaporator based on Graphene/MoO3-x coated porous nickel for water purification
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Jiayi Shen, Jian Tian, Ruiqi Xu, Na Wei, Like Gong, Qi Li, Hongzhi Cui, Chengzhi Li, and Jian Li
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Materials science ,Energy conversion efficiency ,Evaporation ,Filtration and Separation ,Portable water purification ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Desalination ,Analytical Chemistry ,020401 chemical engineering ,Wastewater ,Chemical engineering ,Seawater ,0204 chemical engineering ,0210 nano-technology ,Absorption (electromagnetic radiation) ,Evaporator - Abstract
Solar water evaporation is a promising method for water purification. However, the current photothermal conversion efficiency requires further improvement. Herein, a novel structure (Ni-G-MoO3-x) consisting of graphene (G) and MoO3-x coated porous nickel (Ni) is developed by combining facile chemical vapor deposition (CVD) with hydrothermal methods. The optical absorption and photothermal conversion efficiency of the materials were improved by oxygen vacancies (OVs). The as-prepared solar evaporator exhibits excellent light absorption (96%), good wettability and high conversion efficiency (95%) under 1 sun illumination. In particular, the super hydrophilicity of the evaporator can spontaneously transfer the surface salt back to the bulk seawater in the dark conditions. As a result, a stable evaporation rate can be achieved with the self-driven salt-resistant material in the evaporation cycle of more than three days. Furthermore, the evaporator has an excellent desalination ability and can extract fresh water resources from a variety of water sources (seawater, industrial waste water and organic dye wastewater) through light-to-heat conversion water evaporation technology. This work provides a fundamental guidance and insights on practical applications, thus helping to develop a highly efficient solar evaporator for clean water production. more...
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- 2021
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17. The angle of repose and size segregation of iron ore granules: DEM analysis and experimental investigation
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Tom Honeyands, Roberto Moreno-Atanasio, Chengzhi Li, and Damien O’Dea
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Materials science ,General Chemical Engineering ,Rolling resistance ,Granule (cell biology) ,Mineralogy ,02 engineering and technology ,engineering.material ,Dissipation ,021001 nanoscience & nanotechnology ,Kinetic energy ,Angle of repose ,020401 chemical engineering ,Iron ore ,Vertical direction ,engineering ,0204 chemical engineering ,Composite material ,0210 nano-technology ,Pile - Abstract
We have developed a DEM model to study the packing characteristics of iron ore granules. Two important indices in characterising the packing of granules, i.e. the angle of repose (for packing stability) and a size segregation index, were obtained from the simulations. The comparisons of the simulated and experimental angle of repose and size segregation indices showed good agreement, demonstrating that the developed model is capable of predicting the behaviour of iron ore granules during pile formation. The simulation results show that the angle of repose of iron ore granules was greatly influenced by granule size, sliding and rolling friction coefficients. A decrease in granule size or an increase in either the sliding or rolling friction coefficients significantly increased the kinetic energy dissipation rate of the discharged granules during the packing process. Therefore, an increase in granule pile stability was observed. The simulation results also demonstrated the presence of significant size segregation of iron ore granules in the pile in the horizontal direction. The average granule size in the outer section of the pile was relatively larger than that in the central section. However, in the vertical direction, due to the interaction of multiple segregation mechanisms, size segregation was not clearly observed. more...
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- 2017
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18. Making Breakthroughs in the Turbulent Decade: China’s Space Technology During the Cultural Revolution
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Dehui Zhang, Danian Hu, and Chengzhi Li
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Rocket (weapon) ,Cultural revolution ,Space technology ,060101 anthropology ,05 social sciences ,06 humanities and the arts ,Space (commercial competition) ,050905 science studies ,History and Philosophy of Science ,Economy ,Law ,Political science ,Space program ,0601 history and archaeology ,Christian ministry ,0509 other social sciences ,China - Abstract
This article discusses why Chinese space programs were able to develop to the extent they did during the turbulent decade of the Cultural Revolution (1966-1976). It first introduces briefly what China had accomplished in rocket and missile technology before the Cultural Revolution, including the establishment of a system for research and manufacturing, breakthroughs in rocket technology, and programs for future development. It then analyzes the harmful impacts of the Cultural Revolution on Chinese space programs by examining activities of contemporary mass factions in the Seventh Ministry of Machinery Industry. In the third section, this article presents the important developments of Chinese space programs during the Cultural Revolution and explores briefly the significance of these developments for the future and overall progress in space technology. Finally, it discusses the reasons for the series of developments of Chinese space technology during the Cultural Revolution. This article concludes that, although the Cultural Revolution generated certain harmful impacts on the development of Chinese space technology, the Chinese essentially accomplished their scheduled objectives in their space program, both because of the great support of top Chinese leaders, including the officially disgraced Lin Biao and the Gang of Four, and due to the implementation of many effective special measures. more...
- Published
- 2017
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19. Synthesis and photoluminescence control of Ca10.5–1.5xLax(PO4)7:Eu2+ phosphors by aliovalent cation substitution
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Jilin Zhang, Yanting Fan, Wenli Zhou, Miao Tang, Liping Yu, Chengzhi Li, Zhongxian Qiu, and Shixun Lian
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Valence (chemistry) ,Photoluminescence ,Chemistry ,Inorganic chemistry ,Phosphor ,02 engineering and technology ,Crystal structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Inorganic Chemistry ,Crystallography ,symbols.namesake ,Materials Chemistry ,Ceramics and Composites ,symbols ,Photoluminescence excitation ,Diffuse reflection ,Physical and Theoretical Chemistry ,0210 nano-technology ,Luminescence ,Raman spectroscopy - Abstract
A range of Ca 10.5-1.5 x La x (PO 4 ) 7 :Eu 2+ phosphors were synthesized by high temperature solid state method. Subsequently we studied the crystal structures and luminescent properties through X-ray diffraction, photoluminescence and photoluminescence excitation, diffuse reflection spectra, Raman spectra and decay curves systematically. Based on the special crystal structure of β -Ca 3 (PO 4 ) 2 :Eu 2+ , its emission undergoes a variation from violet–blue to cyan through introducing La 3+ . The substitution of La 3+ for Ca 2+ could form some cation vacancies in Ca(4) sites according to the scheme 3Ca 2+ = 2La 3+ + □ due to the different ion valence, which compels Eu 2+ to migrate from Ca(4) site to other sites. Additionally, the formation of the cation vacancies can further reduce the thermal stability of phosphors. more...
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- 2017
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20. Ho 3+ /Yb 3+ co-doped TeO 2 -BaF 2 -Y 2 O 3 glasses for ∼1.2 μm laser applications
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Shijie Jia, Chengzhi Li, Chuanfei Yao, Shunbin Wang, Guanshi Qin, Weiping Qin, and Zhixu Jia
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2 μm laser ,Materials science ,Analytical chemistry ,Nanotechnology ,02 engineering and technology ,01 natural sciences ,law.invention ,010309 optics ,Inorganic Chemistry ,Magazine ,law ,0103 physical sciences ,Fiber ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,Spectroscopy ,Laser diode ,Organic Chemistry ,021001 nanoscience & nanotechnology ,Emission intensity ,Fluorescence ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,0210 nano-technology ,Co doped ,Excitation - Abstract
Intense ∼1.2 μm fluorescence is observed in Ho 3+ /Yb 3+ co-doped TeO 2 -BaF 2 -Y 2 O 3 glasses under 915 nm laser diode excitation. The 1.2 μm emission can be ascribed to the transition 5 I 6 → 5 I 8 of Ho 3+ . With the introducing of BaF 2 , the content of OH in the glasses drops markedly, and the 1.2 μm emission intensity increases gradually as increasing the concentration percentage of BaF 2 . Furthermore, microstructured fibers based on the TeO 2 -BaF 2 -Y 2 O 3 glasses are fabricated by using a rod-in-tube method, and a relative positive gain of ∼9.42 dB at 1175.3 nm is obtained in a 5 cm long fiber. more...
- Published
- 2017
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21. Er3+-doped ZnF2-BaF2-SrF2-YF3 fluoride glasses for 2.7 μm laser applications
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Chengzhi Li, Weiping Qin, Shijie Jia, Guanshi Qin, Yasutake Ohishi, Zhipeng Zhao, Chuanfei Yao, and Zhixu Jia
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Active laser medium ,Materials science ,Laser diode ,business.industry ,Mechanical Engineering ,Doping ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Laser ,01 natural sciences ,Emission intensity ,law.invention ,010309 optics ,Mechanics of Materials ,law ,Attenuation coefficient ,0103 physical sciences ,Optoelectronics ,General Materials Science ,0210 nano-technology ,business ,Excitation ,Power density - Abstract
Er3+ doped ZnF2-BaF2-SrF2-YF3 (ZBSY-e) glasses were prepared in a glove box. The absorption coefficient of residual hydroxyl in the glasses was calculated to be ∼0.001 cm−1 at 2.7 μm. Under 978 nm laser diode excitation, intense ∼2.7 μm emissions were observed from the ZBSY-e glasses and the emission intensity was much stronger than that obtained in Er3+-doped fluoroindate, fluorozirconate or fluoroaluminate glasses for a same excitation power density. The efficient ∼2.7 μm emission could be attributed to the relative low phonon energy (420 cm−1) of the ZBSY glass. Our results indicated that the ZBSY-e glass was a potential gain medium for ∼2.7 μm lasers. more...
- Published
- 2018
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22. The self-reduction ability of RE3+ in orthosilicate (RE = Eu, Tm, Yb, Sm): BaZnSiO4-based phosphors prepared in air and its luminescence
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Shixun Lian, Wenli Zhou, Chengzhi Li, Jilin Zhang, Yiting Lin, Yue Han, Liping Yu, and Ziren Niu
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Valence (chemistry) ,Reducing agent ,Mechanical Engineering ,Metals and Alloys ,Phosphor ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,medicine.disease_cause ,01 natural sciences ,0104 chemical sciences ,Ion ,chemistry.chemical_compound ,chemistry ,Mechanics of Materials ,Oxidizing agent ,Materials Chemistry ,medicine ,Orthosilicate ,0210 nano-technology ,Luminescence ,Ultraviolet ,Nuclear chemistry - Abstract
Nominal composition phosphors BaZnSiO 4 :RE (RE = Eu, Tm, Sm, Yb) were synthesized by the conventional solid-state method in air (oxidizing atmosphere, OA) and under 10%H 2 /90%N 2 flow (reductive atmosphere, RA) conditions, respectively. Self-reduction phenomenon, which is a valence change from trivalent rare-earth ions (RE 3+ ) to corresponding divalent state (RE 2+ ) without reducing agent, were observed in the samples of Eu/Tm/Yb-doped BaZnSiO 4 but have not observed in Sm-doped samples. Compared with RA condition, the ca. percent of the reductive concentration of Eu 2+ /Tm 2+ /Yb 2+ in the phosphors BaZnSiO 4 prepared in OA condition are 21%, 15% and 35%, respectively. It was found that both of BaZnSiO 4 :Eu and BaZnSiO 4 :Tm prepared in air show greatly broad band emission peak at 500 nm under the excitation of ultraviolet (UV), which indicated they are potential phosphors for UV-based LED. The factors which are related to self-reduction degree have been also discussed. The successful synthesis of BaZnSiO 4 :RE 2+/3+ phosphors in air provides a new route to obtain other novel orthosilicate-based materials. more...
- Published
- 2017
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23. Periodic orbits in 3-dimensional systems and application to a perturbed Volterra system
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Chengzhi Li, Yicang Zhou, and Zhien Ma
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Applied Mathematics ,0103 physical sciences ,Mathematical analysis ,Invariant manifold ,Periodic orbits ,Perturbation (astronomy) ,010307 mathematical physics ,Uniqueness ,010301 acoustics ,01 natural sciences ,Analysis ,Bifurcation ,Mathematics - Abstract
We give a theorem about the existence of periodic orbits for a 3-dimensional system, then use it to study a perturbation of a 3-dimensional Volterra system, and prove the existence and uniqueness of its periodic orbits on a 2-dimensional invariant manifold. more...
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- 2016
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24. PRELP (proline/arginine-rich end leucine-rich repeat protein) promotes osteoblastic differentiation of preosteoblastic MC3T3-E1 cells by regulating the β-catenin pathway
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Chengzhi Li, Huaxin Wang, Xiumei Zhang, Xiaoyan Zhou, Yazhou Cui, Jinxiang Han, Haiying Li, Liang Shi, and Jing Luan
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0301 basic medicine ,Beta-catenin ,Cellular differentiation ,Biophysics ,Leucine-rich repeat ,Biochemistry ,Small hairpin RNA ,Mice ,03 medical and health sciences ,0302 clinical medicine ,Osteogenesis ,medicine ,Connexin43 ,Animals ,Molecular Biology ,beta Catenin ,Glycoproteins ,Extracellular Matrix Proteins ,Gene knockdown ,Osteoblasts ,biology ,PRELP ,Osteoblast ,Gene Expression Regulation, Developmental ,Cell Differentiation ,3T3 Cells ,Cell Biology ,β-catenin ,Molecular biology ,RUNX2 ,030104 developmental biology ,medicine.anatomical_structure ,Differentiation ,030220 oncology & carcinogenesis ,biology.protein ,Signal transduction ,Signal Transduction - Abstract
Proline/arginine-rich end leucine-rich repeat protein (PRELP) is a collagen-binding proteoglycan highly expressed in the developing bones. Recent studies indicated that PRELP could inhibit osteoclastogenesis as a NF-κB inhibitor. However, its role during osteoblast differentiation is still unclear. In this study, we confirmed that the expression of PRELP increased with the osteogenesis induction of preosteoblastic MC3T3-E1 cells. Down-regulation of PRELP expression by shRNA reduced ALP activity, mineralization and expression of osteogenic marker gene Runx2. Our microarray analysis data suggested that β-catenin may act as a hub gene in the PRELP-mediated gene network. We validated furtherly that PRELP knockdown could inhibit the level of connexin43, a key regulator of osteoblast differentiation by affecting β-catenin protein expression, and its nuclear translocation in MC3T3-E1 preosteoblasts. Therefore, this study established a new role of PRELP in modulating β-catenin/connexin43 pathway and osteoblast differentiation. more...
- Published
- 2016
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25. A coupled DEM-SPH model for moisture migration in unsaturated granular material under oscillation
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Jian Chen, Jingjing Meng, Chengzhi Li, O. Orozovic, and Kenneth Williams
- Subjects
Materials science ,Moisture ,Mechanical Engineering ,02 engineering and technology ,Mechanics ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Granular material ,Discrete element method ,Angle of repose ,Physics::Geophysics ,Smoothed-particle hydrodynamics ,Coupling (physics) ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Mechanics of Materials ,General Materials Science ,0210 nano-technology ,Material properties ,Physics::Atmospheric and Oceanic Physics ,Soil mechanics ,Civil and Structural Engineering - Abstract
Granular materials, such as mineral products, soil and chemical fertilizer, normally contain unsaturated free moisture. This unsaturated moisture could migrate in the granular material and its processing, resulting in handling and safety concerns due to a change in the material properties. In this work, a method of coupling the Discrete Element Method (DEM) and the Smoothed Particle Hydrodynamics (SPH) was proposed to investigate moisture migration in unsaturated granular materials under oscillation. The particles and water were simulated through DEM and SPH, respectively and a python coupling framework was programmed to perform the exchange of particle-fluid interaction forces. Subsequently, experiments with plastic pellets and a coal sample were used to calibrate the models, with DEM calibrated by an angle of repose experiment and draining experiments calibrating the coupled model. Finally, the coupled model was validated by comparing the results to those of experiments involving moisture migration under oscillation. It was found that, compared to measurements, the coupled SPH-DEM model predicted the same moisture migration trend and also provided good agreement for the prediction of the mass of drained water. more...
- Published
- 2020
- Full Text
- View/download PDF
26. Tricolor emitting and energy transfer in the phosphor Ba2ZnSi2O7:Ce3+,Eu3+,Eu2+ for white-LED based near-UV chips
- Author
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Jilin Zhang, Wenli Zhou, Zhongxian Qiu, Chengzhi Li, Shixun Lian, Shengzhi Deng, Maomei Zhang, Chunying Rong, and Liping Yu
- Subjects
Geochemistry and Petrology ,Chemistry ,Energy transfer ,Doping ,Analytical chemistry ,Phosphor ,General Chemistry ,Emission spectrum ,Chromaticity ,Absorption (electromagnetic radiation) ,Excitation ,Ion - Abstract
The red, green and blue (R/G/B) tricolor emitting phosphors Ba 2 ZnSi 2 O 7 co-doped with Ce 3+ and Eu 3+ were synthesized in air atmosphere by a conventional high temperature solid-state reaction technique. All of the excitation spectrum of the phosphor Ba 2 ZnSi 2 O 7 :Ce, Eu showed a strong broad band absorption in the n-UV region whenever monitored by red (630 nm)-emitting or by green (500 nm)- and blue (402 nm)-emitting. Under the excitation of 330 nm, the emission spectrum containing a blue-violet emission band, a green emission and four sharp lines originated from the characteristic transitions of Ce 3+ , Eu 2+ and Eu 3+ ions, of which the relative intensities of the three emission bands could be controlled by the doping concentration of Ce 3+ . The ca. CIE chromaticity coordinates ( x =0.317, y =0.309) of the phosphor Ba 1.94 ZnSi 2 O 7 :0.03Eu,0.01Ce was very close to the standard white ( x =0.33, y =0.33), which suggested that it was a novel single-phased white-light emitting phosphor for LED-based near-UV chip. The mechanisms of energy transfer from Eu 2+ to Eu 3+ via Ce 3+ was also discussed. more...
- Published
- 2015
- Full Text
- View/download PDF
27. Slow divergence integral and its application to classical Liénard equations of degree 5
- Author
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Chengzhi Li and Kening Lu
- Subjects
Singular perturbation ,Class (set theory) ,Degree (graph theory) ,Simple (abstract algebra) ,Applied Mathematics ,Mathematical analysis ,Zero (complex analysis) ,Order (ring theory) ,Uniform property ,Divergence (statistics) ,Analysis ,Mathematics - Abstract
The slow divergence integral is a crucial tool to study the cyclicity of a slow–fast cycle for singularly perturbed planar vector fields. In this paper, we deduce a useful form for this integral in order to apply it to various problems. As an example, we use it to prove that the slow divergence integral along any non-degenerate slow–fast cycle for singular perturbations of classical Lienard equations of degree 5 has at most one zero, and the zero is simple if it exists; hence the cyclicity of any non-degenerate slow–fast cycle in this class of equations is at most 2. Up to now there were many interesting results about Lienard equations of degree 3, 4 and ≥6, but almost nothing is known about degree 5. The result in this paper can be seen as a first stage to study the uniform property for classical Lienard equations of degree 5. more...
- Published
- 2014
- Full Text
- View/download PDF
28. Canard phenomenon for an SIS epidemic model with nonlinear incidence
- Author
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Zhien Ma, Huanping Zhu, Jianquan Li, and Chengzhi Li
- Subjects
Singular perturbation ,Classical mechanics ,Applied Mathematics ,Phenomenon ,Mathematical analysis ,Infection transmission ,Limit (mathematics) ,Parameter space ,Epidemic model ,Nonlinear incidence ,Analysis ,Mathematics - Abstract
By using the singular perturbation theory, especially on canard cycles, the canard phenomenon for an SIS epidemic model with nonlinear incidence is investigated. The phenomenon suggests the existence of disease outbreak in the infection transmission. It is proved that the cyclicity of any possible slow–fast cycle is at most two, that is at most two families of hyperbolic limit cycles or at most one family of limit cycles with multiplicity two can bifurcate from the slow–fast cycle by small perturbations. We also indicate the regions in parameter space where the corresponding slow–fast cycle has cyclicity at most one or at most two. more...
- Published
- 2014
- Full Text
- View/download PDF
29. A Strategy for Synthesizing CaZnOS:Eu2+ Phosphor and Comparison of Optical Properties with CaS:Eu2+
- Author
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Chengzhi Li, Shixun Lian, Zhongxian Qiu, Wenli Zhou, Chunying Rong, Liping Yu, Jilin Zhang, and Shubin Liu
- Subjects
chemistry.chemical_classification ,Photoluminescence ,Mechanical Engineering ,Doping ,Inorganic chemistry ,Metals and Alloys ,Sintering ,chemistry.chemical_element ,Phosphor ,Nanotechnology ,Spectral line ,Ion ,Divalent ,chemistry ,Mechanics of Materials ,Materials Chemistry ,Europium - Abstract
The red-emitting phosphor CaZnOS:Eu 2+ was synthesized from CaCO 3 , ZnS, Eu 2 O 3 and CeCl 3 by controlling the sintering condition. It was found that Ce 3+ ions can play a role of reductant to contribute to the formation of Eu 2+ in CaZnOS matrix under inert protective atmosphere. While the gas flow changed to H 2 /N 2 , the product turned to CaS easily. XRD, photoluminescence spectra, UV–vis and IR absorption spectra were evaluated to investigate the origin of the distinctions of the optical properties and stabilities between the two divalent europium ions doped phosphors CaZnOS:Eu 2+ and CaS:Eu 2+ . The similarities and differences between them were analyzed. more...
- Published
- 2014
- Full Text
- View/download PDF
30. Therapeutic Effects of Focused Ultrasound in 4014 Patients with Symptomatic Cervical Ectopy
- Author
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Xi Xiong, Bin Peng, Youping Li, Chengzhi Li, Jing Li, Wenzhi Chen, and Zhi-biao Wang
- Subjects
Adult ,Employment ,China ,medicine.medical_specialty ,Adolescent ,Acoustics and Ultrasonics ,Biophysics ,Comorbidity ,Logistic regression ,Risk Assessment ,Cervical ectopy ,Focused ultrasound ,Young Adult ,Age Distribution ,Postoperative Complications ,Internal medicine ,Prevalence ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Young adult ,Aged ,Aged, 80 and over ,Radiological and Ultrasound Technology ,business.industry ,Therapeutic effect ,Middle Aged ,Uterine Cervical Dysplasia ,medicine.disease ,Surgery ,Clinical trial ,Treatment Outcome ,High-Intensity Focused Ultrasound Ablation ,Female ,Uterine Hemorrhage ,business ,Risk assessment - Abstract
This study aimed to explore the therapeutic effect of focused ultrasound (FU) therapy in patients with symptomatic cervical ectopy. 4677 patients with symptomatic cervical ectopy were enrolled and treated with FU. Three months after treatment, we analyzed the therapeutic effects and the adverse reactions in 4014 cases with complete records. All influential factors were also analyzed with logistic regression analysis. For the treatment of symptomatic cervical ectopy, the effective rate of FU was 99.8%, and the cure rate was 72.52%. Bleeding that either reached or exceeded normal menstrual volume occurred in 12 cases. Logistic regression analysis showed that the degree of illness, vaginal cleanliness, economic level, occupation, age and artificial abortion frequency were all influential factors. Focused ultrasound is a promising new therapeutic option for the treatment of symptomatic cervical ectopy. Additionally, it can be widely used for a variety of patients. more...
- Published
- 2013
- Full Text
- View/download PDF
31. Canard cycles for predator–prey systems with Holling types of functional response
- Author
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Chengzhi Li and Huaiping Zhu
- Subjects
Limit periodic set ,Singular perturbation ,Work (thermodynamics) ,Canard cycle ,Applied Mathematics ,010102 general mathematics ,Mathematical analysis ,Functional response ,Function (mathematics) ,Parameter space ,01 natural sciences ,010101 applied mathematics ,Set (abstract data type) ,Predator–prey systems ,Holling type response ,Limit (mathematics) ,0101 mathematics ,Divergence (statistics) ,Analysis ,Mathematics - Abstract
By using the singular perturbation theory developed by Dumortier and Roussarie and recent work of De Maesschalck and Dumortier, we study the canard phenomenon for predator–prey systems with response functions of Holling types. We first develop a formula for computing the slow divergence integrals. By using the formula we prove that for the systems with the response function of Holling types III and IV the cyclicity of any limit periodic set is at most two, that is at most two families of hyperbolic limit cycles or at most one family of limit cycles with multiplicity two can bifurcate from the limit periodic set by small perturbations. We also indicate the regions in parameter space where the corresponding limit periodic set has cyclicity at most one or at most two. more...
- Published
- 2013
- Full Text
- View/download PDF
32. A new Chebyshev family with applications to Abel equations
- Author
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Joan Torregrosa, Chengzhi Li, and Armengol Gasull
- Subjects
Chebyshev polynomials ,Applied Mathematics ,Mathematical analysis ,Abel equation ,Chebyshev iteration ,Chebyshev's sum inequality ,Chebyshev family ,Abel's identity ,Applied mathematics ,Chebyshev equation ,Chebyshev nodes ,Abel's test ,Analysis ,Mathematics - Abstract
Agraïments: The second author is partially supported by NSFC-10831003 and by AGAUR grant number 2009PIV00064. We prove that a family of functions defined through some definite integrals forms an extended complete Chebyshev system. The key point of our proof consists of reducing the study of certain Wronskians to the Gram determinants of a suitable set of new functions. Our result is then applied to give upper bounds for the number of isolated periodic solutions of some perturbed Abel equations. more...
- Published
- 2012
- Full Text
- View/download PDF
33. A white light emitting phosphor Sr1.5Ca0.5SiO4:Eu3+, Tb3+, Eu2+ for LED-based near-UV chip: Preparation, characterization and luminescent mechanism
- Author
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Chengzhi Li, Xi Chen, Liping Yu, Shixun Lian, Junfeng Zhao, and Chunying Rong
- Subjects
business.industry ,Biophysics ,Analytical chemistry ,Phosphor ,General Chemistry ,Condensed Matter Physics ,Biochemistry ,Atomic and Molecular Physics, and Optics ,Photon upconversion ,chemistry.chemical_compound ,chemistry ,Optoelectronics ,Orthosilicate ,Emission spectrum ,Chromaticity ,business ,Luminescence ,Excitation ,Diode - Abstract
In this work, we report preparation, characterization and luminescent mechanism of a phosphor Sr 1.5 Ca 0.5 SiO 4 :Eu 3+ ,Tb 3+ ,Eu 2+ (SCS:ETE) for white-light emitting diode (W-LED)-based near-UV chip. Co-doped rare earth cations Eu 3+ , Tb 3+ and Eu 2+ as aggregated luminescent centers within the orthosilicate host in a controlled manner resulted in the white-light phosphors with tunable emission properties. Under the excitation of near-UV light (394 nm), the emission spectra of these phosphors exhibited three emission bands: one broad band in the blue area, a second band with sharp lines peaked in green (about 548 nm) and the third band in the orange–red region (588–720 nm). These bands originated from Eu 2+ 5d→4f, Tb 3+ 5 D 4 → 7 F J and Eu 3+ 5 D 0 → 7 F J transitions, respectively, with comparable intensities, which in return resulted in white light emission. With anincrease of Tb 3+ content, both broad Eu 2+ emission and sharp Eu 3+ emission increase. The former may be understood by the reduction mechanism due to the charge transfer process from Eu 3+ to Tb 3+ , whereas the latter is attributed to the energy transfer process from Eu 2+ to Tb 3+ . Tunable white-light emission resulted from the system of SCS:ETE as a result of the competition between these two processes when the Tb 3+ concentration varies. It was found that the nominal composition Sr 1.5 Ca 0.5 SiO 4 :1.0%Eu 3+ , 0.07%Tb 3+ is the optimal composition for single-phased white-light phosphor. The CIE chromaticity calculation demonstrated its potential as white LED-based near-UV chip. more...
- Published
- 2011
- Full Text
- View/download PDF
34. Microwave-assisted synthesis of flower-like Ag–BiOCl nanocomposite with enhanced visible-light photocatalytic activity
- Author
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Libo Wang, Chengzhi Li, Aiguo Zhou, Qianku Hu, Xinxin Cao, Yupeng Gao, and Zhengyang Li
- Subjects
Materials science ,Nanocomposite ,business.industry ,Mechanical Engineering ,Condensed Matter Physics ,Field emission microscopy ,chemistry.chemical_compound ,Semiconductor ,chemistry ,Chemical engineering ,Mechanics of Materials ,Transmission electron microscopy ,Rhodamine B ,Photocatalysis ,General Materials Science ,Composite material ,Photodegradation ,business ,Visible spectrum - Abstract
Flower-like BiOCl and Ag–BiOCl nanocomposite have been successfully fabricated via a microwave irradiation process. The structure and morphology of the samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The photocatalytic property of the BiOCl and Ag–BiOCl nanocomposite was evaluated by photodegradation of Rhodamine B (RhB) under visible light illumination. Results of photodegradation tests reveal that the Ag–BiOCl nanocomposite has much better photocatalytic activity than pure BiOCl. The excellent photocatalytic activity can be ascribed to the high effective electron–hole separation which results in the significant improvement of the photocatalytic activity of BiOCl. more...
- Published
- 2014
- Full Text
- View/download PDF
35. A cubic system with thirteen limit cycles
- Author
-
Chengzhi Li, Changjian Liu, and Jiazhong Yang
- Subjects
Discrete mathematics ,Limit cycles ,Planar ,Cubic system ,Applied Mathematics ,Limit cycle ,Abelian integral ,Cubic form ,Hilbert's 16th problem ,Limit (mathematics) ,Abelian group ,Analysis ,Mathematics - Abstract
We construct a planar cubic system and demonstrate that it has at least 13 limit cycles. The construction is essentially based on counting the number of zeros of some Abelian integrals.
- Published
- 2009
- Full Text
- View/download PDF
36. A Comparison Between Ultrasound Therapy and Laser Therapy for Symptomatic Cervical Ectopy
- Author
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Jianhua Peng, Chengzhi Li, Yuming Liu, Jinyun Chen, Zhibiao Wang, Deping Zhou, and Wen-Zhi Chen
- Subjects
Adult ,medicine.medical_specialty ,Acoustics and Ultrasonics ,Side effect ,Ultrasonic Therapy ,Biophysics ,Cervicitis ,Postoperative Hemorrhage ,law.invention ,Young Adult ,Randomized controlled trial ,law ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Cervix ,Leukorrhea ,Radiological and Ultrasound Technology ,business.industry ,Pelvic pain ,Ultrasound ,Therapeutic effect ,Middle Aged ,medicine.disease ,Uterine Cervicitis ,Surgery ,Treatment Outcome ,Vaginal Discharge ,medicine.anatomical_structure ,Female ,Laser Therapy ,medicine.symptom ,business - Abstract
The purpose of this study was to compare the clinical efficacy of ultrasound (US) therapy and laser therapy in patients with symptomatic benign ectopy of the uterine cervix. Patients with symptomatic benign ectopy of the cervix (n = 200) were enrolled in this study. Abundant leukorrhea, contact bleeding, recurrent cervicitis and pelvic pain were also evaluated. Patients were allocated alternately to the US and laser groups. In the laser group, Nd: YAG laser was used for tissue vaporization destruction. In the US group, the therapeutic US device Seapostar (Chongqing Haifu [HIFU] Technology, Co. Ltd., Chongqing, China) was applied. Neither anesthesia nor analgesia was used. Results showed that patients in both groups tolerated the procedure well and had excellent treatment outcomes. A symptomatic cure rate of 97.33% was obtained in the US group, and 98.81% was obtained in the laser group (p > 0.05). Ectopy areas were managed with a success rate of 95.95% in the US group, and 96.43% in the laser group (p > 0.05). The rate of side effects (including vaginal reactive discharge and colporrhagia) was found to be lower in the US group than that in the laser group. Mild-to-moderate bleeding occurred in US group (8.42%) and laser group (45.56%). The bleeding rate in the US group is significantly lower than that in the laser group (p < 0.01). We conclude that focused US can treat symptomatic ectopy of the cervix successfully, with excellent clinical results and minimal risk. Focused US therapy appears to be a promising new treatment method for symptomatic ectopy of the uterine cervix. more...
- Published
- 2008
- Full Text
- View/download PDF
37. Geometrical effect on dislocation nucleation at crystal surface nanostructures
- Author
-
Guanshui Xu and Chengzhi Li
- Subjects
Dislocation creep ,Materials science ,Condensed matter physics ,Applied Mathematics ,General Engineering ,Nucleation ,Geometry ,Atomic units ,Crystal ,Condensed Matter::Materials Science ,Computational Mathematics ,Peierls stress ,Dislocation ,Analysis ,Stress concentration ,Surface states - Abstract
Crystal surface nanostructures such as steps and trenches in microelectronic layer structures have been considered as stress concentrators that may facilitate dislocation nucleation. Quantitative characterization of the critical condition of this atomic scale process is of considerable interest for the development of high performance electronic devices. This paper addresses this issue using a multiscale approach based on the variational boundary integral formulation of the Peierls–Nabarro dislocation model. By representing the profiles of embryonic dislocations as the relative displacements between the two adjacent atomic layers along the slip planes, the critical conditions for dislocation nucleation are obtained by solving the stress dependent activation energies required to activate embryonic dislocations from their stable to unstable saddle point configurations. The geometrical effect of surface nanostructures such as steps and trenches on dislocation nucleation is ascertained quantitatively. Our results show that the atomic scale surface nanostructures can reduce the critical stress for dislocation nucleation by nearly an order of magnitude and the trench configurations are more prone to dislocation nucleation than the step configurations. Nucleation of versatile dislocations in multiple slip systems at crystal surfaces may be attributed surface nanostructures of a variety of geometries. more...
- Published
- 2007
- Full Text
- View/download PDF
38. Perturbations of symmetric elliptic Hamiltonians of degree four
- Author
-
Pavao Mardešić, Chengzhi Li, and Robert Roussarie
- Subjects
Chebychev property ,Degree (graph theory) ,Applied Mathematics ,Mathematical analysis ,Bifurcation diagram ,Annulus (mathematics) ,Unfolding symmetric Hamiltonian systems ,Parameter space ,Melnikov functions ,unfolding symmetric Hamiltonian systems ,Displacement function ,Principal part ,Limit (mathematics) ,Analysis ,Sign (mathematics) ,Mathematics - Abstract
In this paper four-parameter unfoldings Xλ of symmetric elliptic Hamiltonians of degree four are studied. We prove that in a compact region of the period annulus of X0 the displacement function of Xλ is sign equivalent to its principal part, which is given by a family induced by a Chebychev system; and we describe the bifurcation diagram of Xλ in a full neighborhood of the origin in the parameter space, where at most two limit cycles can exist for the corresponding systems. more...
- Published
- 2006
- Full Text
- View/download PDF
39. Preparation and Characterization of Red Luminescent Ca0.8Zn0.2TiO3: Pr3+, Na+ Nanophosphor
- Author
-
Shixun Lian, Chengzhi Li, Chenggang Zuo, Huajing Zhang, and Dulin Yin
- Subjects
Materials science ,Metal ions in aqueous solution ,Mineralogy ,Sintering ,General Chemistry ,law.invention ,chemistry.chemical_compound ,chemistry ,Geochemistry and Petrology ,law ,Particle size ,Crystallization ,Thermal analysis ,Luminescence ,Ethylene glycol ,Sol-gel ,Nuclear chemistry - Abstract
Nanophosphor with the nominal composition of Ca 0.8 Zn 0.2 TiO 3 :Pr 3+ , Na + (CZTOPN) was synthesized at relatively low temperature by the sol-gel method. Metal ions were dispersed by citric acid in ethylene glycol solvent and then react with Ti(OC 4 H 9 ) 4 to form sol and gel. The decomposition process of the precursor, and crystallization and particle size of CZTOPN were examined by thermal analysis (TG-DSC), powder X-ray diffraction (XRD), and scan election microscopy (SEM). Results of TG-DSC and XRD reveal that the composition of Ca 0.8 Zn 0.2 TiO 3 :Pr 3+ , Na + changes with the sintering temperature. SEM data indicate that the diameter of particles is under 50 nm even if the sintering temperature increases to 1000 °C. In contrast to a solid state reaction, the excitation spectra of samples synthesized by the sol-gel method shift blue about 10 nm and the emission intensity at 617 nm increases significantly. more...
- Published
- 2006
- Full Text
- View/download PDF
40. The cyclicity of the elliptic segment loops of the reversible quadratic Hamiltonian systems under quadratic perturbations
- Author
-
Robert Roussarie and Chengzhi Li
- Subjects
Pure mathematics ,Integrable system ,Applied Mathematics ,Mathematical analysis ,Bifurcation diagram ,Ellipse ,Hamiltonian system ,symbols.namesake ,Line segment ,Quadratic equation ,Conic section ,Cyclicity of elliptic segment loops ,symbols ,Reversible quadratic Hamiltonian systems ,Hamiltonian (quantum mechanics) ,Analysis ,Mathematics - Abstract
Denote by Q H and Q R the Hamiltonian class and reversible class of quadratic integrable systems. There are several topological types for systems belong to Q H ∩ Q R . One of them is the case that the corresponding system has two heteroclinic loops, sharing one saddle-connection, which is a line segment, and the other part of the loops is an ellipse. In this paper we prove that the maximal number of limit cycles, which bifurcate from the loops with respect to quadratic perturbations in a conic neighborhood of the direction transversal to reversible systems (called in reversible direction), is two. We also give the corresponding bifurcation diagram. more...
- Published
- 2004
- Full Text
- View/download PDF
41. Perturbation from an elliptic Hamiltonian of degree four—IV figure eight-loop
- Author
-
Freddy Dumortier and Chengzhi Li
- Subjects
Differential equation ,Applied Mathematics ,Mathematical analysis ,Upper and lower bounds ,symbols.namesake ,Limit cycle ,symbols ,Elliptic integral ,Gravitational singularity ,Vector field ,Hamiltonian (quantum mechanics) ,Analysis ,Saddle ,Mathematics - Abstract
The paper deals with Liénard equations of the form ẋ=y, ẏ=P(x)+yQ(x) with P and Q polynomials of degree, respectively, 3 and 2. Attention goes to perturbations of the Hamiltonian vector fields with an elliptic Hamiltonian of degree four, exhibiting a figure eight-loop. It is proved that the least upper bound of the number of zeros of the related elliptic integral is five, and this is a sharp bound, multiplicity taken into account. Moreover, if restricting to the level curves “inside” a saddle loop or “outside” the figure eight-loop the sharp upper bound is respectively two or four; also the multiplicity of the zeros is at most four. This is the last one in a series of papers on this subject. The results of this paper, together with (J. Differential Equations 176 (2001) 114; J. Differential Equations 175 (2001) 209; J. Differential Equations, to be published), largely finish the study of the cubic perturbations of the elliptic Hamiltonians of degree four and presumably provide a complete description of the number and the possible configurations of limit cycles for cubic Liénard equations with small quadratic damping. As a special case, we obtain a configuration of four limit cycles surrounding three singularities together with a “small” limit cycle which surrounds one of the singularities. more...
- Published
- 2003
- Full Text
- View/download PDF
42. The measurement and control of diameter in large-scale part processing
- Author
-
L. Yang, Xiping Xu, Chengzhi Li, Xiuhua Fu, and Guoyu Zhang
- Subjects
Engineering ,Data processing ,business.industry ,Acoustics ,Metals and Alloys ,Grating ,Signal ,Industrial and Manufacturing Engineering ,Displacement (vector) ,Computer Science Applications ,Dimension (vector space) ,Control theory ,Modeling and Simulation ,Control system ,Microcomputer ,Ceramics and Composites ,business - Abstract
Based on laser-scanned measuring technology, a method of on-line dynamic non-contact measurement and feedback control of processing dimensions, i.e. a double-edges laser-scanned large diameter on-line dynamic measurement and control system, is presented, which can be used to measure diameter in large-scale machine part processing. In this paper, the working principle, the overall structure and the microcomputer real-time control and data processing, of the system are discussed in detail, the method of double-edges scanned large diameter dimension measurement and control being theoretically analyzed, its possibility then being verified by experiments into the turning of large diameters machine parts by a vertical lathe. The system adopts the measuring scheme of double-edges laser-scanning combined with grating displacement measurement. The two-edges characteristic information of the measured diameter is given by the double-edges laser-scanned measuring system, the non-contact measurement of the large diameter dimension being realized to combine with the grating displacement-measuring system. The main controller gives out a feedback control signal by means of the measured results, and controls the advance and retreat of the lathe tool by the servo-control system of the vertical lathe to realize on-line dynamic non-contact measurement and control in processing. more...
- Published
- 2002
- Full Text
- View/download PDF
43. Bifurcation of a class of planar non-Hamiltonian integrable systems with one center and one homoclinic loop
- Author
-
Chengzhi Li and Jiang Yu
- Subjects
Hopf bifurcation ,Integrable system ,Applied Mathematics ,Mathematical analysis ,Saddle-node bifurcation ,Picard–Fuchs equation ,symbols.namesake ,symbols ,Homoclinic bifurcation ,Homoclinic orbit ,Hamiltonian (quantum mechanics) ,Bifurcation ,Analysis ,Mathematical physics ,Mathematics - Published
- 2002
- Full Text
- View/download PDF
44. Linear Estimation of the Number of Zeros of Abelian Integrals for Some Cubic Isochronous Centers
- Author
-
Weigu Li, Jaume Llibre, Chengzhi Li, and Zhifen Zhang
- Subjects
Polynomial ,Degree (graph theory) ,Conic section ,Applied Mathematics ,Mathematical analysis ,Astrophysics::Earth and Planetary Astrophysics ,Limit (mathematics) ,Center (group theory) ,Singular point of a curve ,Abelian group ,Type (model theory) ,Analysis ,Mathematics - Abstract
This paper consists of two parts. In the first part we study the relationship between conic centers (all orbits near a singular point of center type are conics) and isochronous centers of polynomial systems. In the second part we study the number of limit cycles that bifurcate from the periodic orbits of cubic reversible isochronous centers having all their orbits formed by conics, when we perturb such systems inside the class of all polynomial systems of degree n . more...
- Published
- 2002
- Full Text
- View/download PDF
45. Perturbations from an Elliptic Hamiltonian of Degree Four
- Author
-
Freddy Dumortier and Chengzhi Li
- Subjects
Pure mathematics ,Hamiltonian vector field ,Applied Mathematics ,Mathematical analysis ,Bifurcation diagram ,Upper and lower bounds ,Infimum and supremum ,Half-period ratio ,symbols.namesake ,symbols ,Elliptic integral ,Vector field ,Hamiltonian (quantum mechanics) ,Saddle ,Analysis ,Mathematics - Abstract
The paper deals with Lienard equations of the form x = y , y = P ( x )+ yQ ( x ) with P and Q polynomials of degree respectively 3 and 2. Attention goes to perturbations of the Hamiltonian vector fields with an elliptic Hamiltonian of degree 4 and especially to the study of the related elliptic integrals. Besides some general results the paper contains a complete treatment of the Saddle Loop case and the Two Saddle Cycle case. It is proven that the related elliptic integrals have at most two zeros, respectively one zero, the multiplicity taken into account. The bifurcation diagram of the zeros is also obtained. more...
- Published
- 2001
- Full Text
- View/download PDF
46. Linear estimate of the number of zeros of Abelian integrals for a class of integrable non-Hamiltonian systems
- Author
-
Chengzhi Li, Jaume Llibre, Weigu Li, and Zhifen Zhang
- Subjects
Discrete mathematics ,Abelian integral ,Class (set theory) ,Pure mathematics ,Integrable system ,Applied Mathematics ,Elementary abelian group ,Superintegrable Hamiltonian system ,Abelian group ,Analysis ,Arithmetic of abelian varieties ,Mathematics ,Hamiltonian system - Published
- 2001
- Full Text
- View/download PDF
47. Unfolding of a Quadratic Integrable System with Two Centers and Two Unbounded Heteroclinic Loops
- Author
-
Chengzhi Li, Freddy Dumortier, and Zifen Zhang
- Subjects
Abelian integral ,Quadratic equation ,Phase portrait ,Integrable system ,Applied Mathematics ,Mathematical analysis ,Limit (mathematics) ,Heteroclinic bifurcation ,Bifurcation diagram ,Focus (optics) ,Analysis ,Mathematics - Abstract
In this paper we present a complete study of quadratic 3-parameter unfoldings of some integrable system belonging to the classQR3, and having two centers and two unbounded heteroclinic loops. We restrict to unfoldings that are transverse toQR3, obtain a versal bifurcation diagram and all global phase portraits, including the precise number and configuration of the limit cycles. It is proved that 3 is the maximal number of limit cycles surrounding a single focus, and only the (1, 1)-configuration can occur in case of simultaneous nests of limit cycles. Essentially the proof relies on a careful analysis of a related non-conservative Abelian integral. more...
- Published
- 1997
- Full Text
- View/download PDF
48. A Criterion for Determining the Monotonicity of the Ratio of Two Abelian Integrals
- Author
-
Zhifen Zhang and Chengzhi Li
- Subjects
Discrete mathematics ,Abelian integral ,Applied Mathematics ,Monotonic function ,Elementary abelian group ,Abelian group ,Analysis ,Rank of an abelian group ,Arithmetic of abelian varieties ,Mathematics - Abstract
A new method to determine the monotonicity of the ratio of two Abelian integrals is given. We find two criterion functions defined directly by the functions which appear in the Abelian integrals. The monotonicities of the criterion functions imply the monotonicity of the ratio of the Abelian integrals. By using this criterion, several known results can be deduced easier, and some new results are obtained. more...
- Published
- 1996
- Full Text
- View/download PDF
49. X* plus Axiom A Does Not Imply No-Cycle
- Author
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Chengzhi Li and Lan Wen
- Subjects
Mathematics::Logic ,Axiom independence ,Applied Mathematics ,Mathematical economics ,Axiom A ,Analysis ,Mathematics - Abstract
An example is presented to indicate that X * plus Axiom A does not imply the no-cycle condition.
- Published
- 1995
- Full Text
- View/download PDF
50. The Chinese GNSS—System development and policy analysis
- Author
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Chengzhi, Li, primary
- Published
- 2013
- Full Text
- View/download PDF
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