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Search Results: 1 - 10 of 127182 matches for " Yongfeng Li "
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On the Uniqueness Theorem of Time-Harmonic Electromagnetic Fields  [PDF]
Yongfeng Gui, Pei Li
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2011, DOI: 10.4236/jemaa.2011.31003
Abstract: The uniqueness theorem of time-harmonic electromagnetic fields, which is the theoretical basis of boundary value problem (BVP) of electromagnetic fields, is reviewed. So far there are many versions of the statements and proofs on the theorem. However, there exist some limitations and lack of strictness in these versions, for instance, the discussion of the uniqueness of solution without considering the existence of solution and the lack of strictness in the case of loss-less medium. In contrast with the traditional statements and proofs, this paper introduces some important conclusions on operator equation from modern theory of partial differential equation (PDE) and attempts to solve the problems on the existence and uniqueness of the solution to operator equation which is derived from Maxwell’s equations of time-harmonic electromagnetic fields. This method provides a novel and rigorous approach to discuss and solve the existence and uniqueness of the solution to time- harmonic fields in the new mathematical framework. Some important conclusions are presented.
The Distribution and Morphology Alterations of Microfilaments and Microtubules in Mesophyll Cells and Root-Tip Cells of Wheat Seedlings under Enhanced Ultraviolet-B Radiation  [PDF]
Limei Gao, Yongfeng Li, Aihua Guo, Jingru Zhai, Rong Han
American Journal of Plant Sciences (AJPS) , 2014, DOI: 10.4236/ajps.2014.522358
Abstract:
The distribution and morphology alterations of microfilaments and microtubules in the mesophyll cells and root-tip cells of wheat seedlings, which had been radiated by enhanced ultraviolet-B (10.08 KJ·m-2·d-1), were examined through the confocal laser scanning microscope (Model FV1000, Olympus, Japan). Microtubule was labeled with an indirect immunofluorescence staining method, and microfilament was labeled with fluorescein isothiocyanate-phalloidin (FITC-Ph) as probes. The results indicated that microtubules in mesophyll cells, compared with the controls, would be depolymerized significantly, and dispersed randomly showing some spots or short rods in the cytoplasm, under the enhanced UV-B radiation condition. The microtubule bundles tended to be diffused, and the fluorescence intensity of that significantly decreased. The distribution pattern of microfilaments, which usually arranged parallelly in control cells, was broken up by enhanced UV-B radiation. We further investigated the distribution and morphology of microtubules in root-tip cells during every stage of cell division, and found that these aberrant phenomena of microtubules were often associated with abnormal cell division. Our findings suggested that the distribution, morphology and structure of cytoskeleton in mesophyll cells and root-tip cells of wheat seedlings would be affected by enhanced UV-B radiation, which might be related to abnormal cell division caused by enhanced UV-B radiation as an extracellular signal.
The Size and Shape Dependence of Ferromagnetism in Nanomagnets
Ying Li,Yongfeng Li,Tianxing Wang
Journal of Nanomaterials , 2012, DOI: 10.1155/2012/897203
Abstract: The size and shape dependence of dynamic behaviors of nanomagnets is studied by the kinetic Monte Carlo method based on the transition state theory. We analyze the hysteresis curves of the nanomagnet systems with different shapes (or spin array patterns) in the presence of an external magnetic field. The results show that the magnetization of the chain-shaped nanomagnet is more sensitive to the applied field than that of the oblong-shaped or bulk-shaped systems. For the same magnetic nanostructure, the coercive field presents an exponential decay with temperature. Moreover, the coercive field is found to be strongly dependent on the effective coordination number, which has different values corresponding to those systems of different size and shapes (spin array patterns).
A review of plasma liquid interactions for nanomaterial synthesis
Qiang Chen,Junshuai Li,Yongfeng Li
Physics , 2014, DOI: 10.1088/0022-3727/48/42/424005
Abstract: In this review, we have summarized the recent advances and present conditions of the nanomaterials synthesis from the plasma-liquid interactions. A theoretical analysis for the nanomaterials synthesis process is presented by analyzing the experimental data. Besides the theoretical analysis, the practical applications in several nanomaterials syntheses of the the plasma-liquid interactions are also presented.
C59N Peapods Sensing the Temperature
Yongfeng Li,Toshiro Kaneko,Rikizo Hatakeyama
Sensors , 2013, DOI: 10.3390/s130100966
Abstract: We report the novel photoresponse of nanodevices made from azafullerene (C 59N)-encapsulated single-walled carbon nanotubes (C 59N@SWNTs), so called peapods. The photoconducting properties of a C 59N@SWNT are measured over a temperature range of 10 to 300 K under a field-effect transistor configuration. It is found that the photosensitivity of C 59N@SWNTs depends very sensitively on the temperature, making them an attractive candidate as a component of nanothermometers covering a wide temperature range. Our results indicate that it is possible to read the temperature by monitoring the optoelectronics signal of C 59N@SWNTs. In particular, sensing low temperatures would become more convenient and easy by giving a simple light pulse.
Dosimetric Study of Coplanar and Non-Coplanar Intensity-Modulated Radiation Therapy Planning for Esophageal Carcinoma  [PDF]
Ying Li, Bing Liu, Fushan Zhai, Yongfeng Yang, Ming Liu, Chaoen Bao, Qingxiang Zhou
International Journal of Medical Physics,Clinical Engineering and Radiation Oncology (IJMPCERO) , 2013, DOI: 10.4236/ijmpcero.2013.24018
Abstract: Purpose: To compare the dosimetric impact of coplanar intensity modulated radiation therapy (IMRT) and non-coplanar IMRT for the esophageal carcinoma. Methods: There are forty-five esophageal carcinoma patients, fifteen of whom were cervical and upper thoracic (Group 1) and thirty were middle and lower thoracic (Group 2). Gross tumor volume (GTV), clinical target volume (CTV), and organs at risk (OAR) were contoured by the chief physician in the CMS-XiO treatment planning system. For each patient, one coplanar plan and two non-coplanar plans have been created using the same physical objective function. A detailed dose-volume histogram (DVH) comparison among three plans was then carried out in a tabulated format. Results: 1) In Group 1 patients with PTV volume less than 100cc, the mean dose and dose gradient of non-coplanar plan were much better than those in coplanar plan. 2) In Group 2 patients, the conformity index (CI) for coplanar and two non-coplanar plans were 0.69 ± 0.13, 0.41 ± 0.13, and 0.68 ± 0.15, respectively. The V5, V10, V20, and the mean dose to the lung were lower in the non-coplanar plans compared to ones in coplanar plan. However, the non-coplanar plans resulted in an increase in a dose to the heart, but the dose was still within heart toxicity tolerance. Conclusion: For Group 1 patients, the
Analytical method of minimum spacing of signalized intersectionson bidirectional two-lane highways
Ma Yongfeng, Yuan Li, Zhang Wenbo
- , 2015, DOI: 10.3969/j.issn.1003-7985.2015.04.020
Abstract: In order to improve the smoothness of traffic flow on bidirectional two-lane highways, an analytical method is proposed to optimize the minimum spacing of the signalized intersections. The minimum signal spacing is determined by two parts, including the necessary distance for stabilizing the traffic flow after it passes through the signalized intersections and the length of the upstream functional area of intersection. For the former, based on the platoon dispersion theory, the stable distance determination problem of traffic flow is studied and a model of dispersion degrees varying with the distance from the upstream intersection is presented, in which the time headway is intended to yield the shifted negative exponential distribution. The parameters of the model for arterial and collector highways are estimated respectively based on the field data. Then, the section at which the slope of dispersion degree curve equals -0.1 is regarded as the beginning of the dispersion stable state. The length of the intersection upstream functional area is determined by three parts, including the distance traveled during perception-reaction time, the distance traveled while a driver decelerates to a stop, and the queue storage length. Based on the above procedures, the minimum signal spacing of each highway category is proposed.
An overview on industrial waste management in China
Yang Yanru,Nie Yongfeng,Li Guoding,
Yang Yanru
,Nie Yongfeng,Li Guoding

环境科学学报(英文版) , 1996,
Abstract: Anoveralldescriptionofindustrialwastewasgivenfromgeneration;treatment,disposalandemissionandcomprehensiveutilization.Inspiteo...
Stability Analysis of Discrete Hopfield Neural Networks with the Nonnegative Definite Monotone Increasing Weight Function Matrix
Jun Li,Yongfeng Diao,Mingdong Li,Xing Yin
Discrete Dynamics in Nature and Society , 2009, DOI: 10.1155/2009/673548
Abstract: The original Hopfield neural networks model is adapted so that the weights of the resulting network are time varying. In this paper, the Discrete Hopfield neural networks with weight function matrix (DHNNWFM) the weight changes with time, are considered, and the stability of DHNNWFM is analyzed. Combined with the Lyapunov function, we obtain some important results that if weight function matrix (WFM) is weakly (or strongly) nonnegative definite function matrix, the DHNNWFM will converge to a stable state in serial (or parallel) model, and if WFM consisted of strongly nonnegative definite function matrix and column (or row) diagonally dominant function matrix, DHNNWFM will converge to a stable state in parallel model.
固体火箭发动机复合材料壳体裙黏接性能分析

LI Yongfeng
, ZHANG Fu, SHEN Zhibin, LI Haiyang

- , 2018, DOI: 10.11887/j.cn.201802006
Abstract: 采用数值计算方法研究复合材料壳体裙连接结构的黏接性能。通过建立纤维缠绕壳体的有限元模型,采用内聚力模型定义裙黏接面的接触关系,引入黏接界面的损伤失效准则,模拟黏接界面的脱黏行为,以此预测裙连接结构的极限承载。同时,研究壳体的轴向和环向应变及黏接面上的剪应力分布情况,以及弹性层的弹性模量与黏接长度对黏接性能的影响。数值算例表明,计算结果与实验数据相吻合,验证了该方法的正确性。所提方法可用于裙连接结构的优化设计中。
The skirt bonding properties of the composite case was analyzed by using the numerical method. The finite element model of the filament wound case was established. The contact of the skirt bonding interface was defined with the cohesive zone model. The damage failure criterion was employed and the debonding of the interface was simulated to predict the ultimate load of the skirt structure. Moreover, the distributions of the axial strain and the hoop strain on the case and the shear stress in the interface were investigated. The effects of the elastic modulus and the bonding length on the ultimate tensile load were studied. Numerical example shows that the results have a good agreement with the experimental data, which can provide validity for the present method. The proposed method can be applied to the optimal design of the skirt structure.
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