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Search Results: 1 - 10 of 25644 matches for " Meifang Dong "
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Control of Unit Power Factor PWM Rectifier  [PDF]
Meifang Xue, Mingzhi He
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.54B023
Abstract: To solve the problem of harmonic pollution to the power grid that caused by traditional diode rectifier and phase controlled rectifier, the unit power factor PWM rectifier is designed. The topology structure of the rectifier circuit is introduced and the double closed-loop control strategy in three-phase stationary coordinate system is analyzed. For the deficiency of control strategy, the control strategy in two-phase synchronous rotating coordinate system is proposed. This makes the independent control of active current and reactive current to be realized. The simulation model of the PWM rectifier is built and the effectiveness of the control method proposed in this paper is verified by simulation.
Megasporogenesis and Female Gametophyte Development of Thellungiella halophila
小盐芥大孢子发生和雌配子体发育

Meifang Dong,Nan Hu,Fude Shang,
董美芳 胡楠
,尚富德

植物学报 , 2006,
Abstract: We observed the course of megasporogenesis and the development of the female gametophyte of Thellungiella halophila to study the relation between the development stages and the morphological characteristics of flower bud, flower and fruit. The ovary is composed of 2 carpels where a parietal placentation is formed, on which many campylotropous ovules grow. The ovule is bitegminous and tenuinucellate. The archesporial cell lies under the nucellus epidermis, which develops into a functional megasporocyte. The megaspore tetrad is linear. The chalazal megaspore develops into an embryo sac of the polygonum type.
Design on the Incentive Contract of University Achievements Commercialization Offices Based on Principal-Agent Theory  [PDF]
Meifang Li, Yongxiang Zhao, Feng Shi
Journal of Service Science and Management (JSSM) , 2010, DOI: 10.4236/jssm.2010.31009
Abstract: Based on principal-agent theory, an incentive contract model of university achievements commercialization offices (UACO) was constructed in this paper, and an optimal incentive contract between university and UACO was researched into. The conclusion indicates that many factors, such as working ability, working willingness, risk aversion degree of UACO, as well as the outside uncertain factors and so on, have important influences on the contract design. The efficiency of commercialization of university inventions has a squared forward growth relation with working ability, a direct proportion with working willingness, and has an inverse proportion with risk aversion degree of UACO and with outside uncertainty. Additionally, the level of hard working of UACO under the condition of information asymmetry is strictly less than that of information symmetry.
Indoor Radio Propagation Model Based on Dominant Path  [PDF]
Yongxiang Zhao, Meifang Li, Feng Shi
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2010, DOI: 10.4236/ijcns.2010.33042
Abstract: When there are bigger obstacles in the indoor environment such as elevator, the radio waves basically can not penetrate it. The contribution of received signal strength by transmission and reflection will be greatly reduced, and most of the time, the radio waves will reach the user by bypass diffraction. Therefore, the traditional path loss model is no longer applicable, and the improved model should be proposed. In this paper, we firstly proposed an indoor radio propagation model based on dominant path in which the received signal strength has nothing to do with the direct distance between user and access point, but is related to the length of dominant path. Then on the basis of dominant path model, the NLOS influence is considered in order to further improve the accuracy of dominant path model. Experimental results demonstrated that the proposed dominant path model can improve the accuracy of traditional path loss model remarkably.
Co-Frequency Interference Suppression Algorithm via Maximum Signal Minus Interference Level
Lingjiang Kong;Meifang Luo
PIER , 2010, DOI: 10.2528/PIER10032307
Abstract: Co-frequency interference problem is severe in shared-spectrum multistatic radar system, leading to detection problems in applications. In order to mitigate the co-frequency interferences, an adaptive pulse compression algorithm based on Maximum Signal Minus Interference Level criterion(MSMIL) is proposed in this paper, the main idea of which is to adaptively design an appropriate filter at each range cell, maximizing the result of signal power minus interference power, so that both range sidelobes and cross-correlation interference can be suppressed. Simulation results show that the algorithm outperforms the traditional multistatic adaptive pulse compression (MAPC) method in interference suppression. Compared with MAPC method, after one iteration step, the output SIR of the proposed algorithm is increased by about 10 dB. And after two iteration steps, it is increased by more than 40 dB. Moreover, it also outperforms the MAPC in convergence speed.
The Strategic Transformation of Automobile Industry in China
Som Techakanjanakit,Meifang Huang
International Journal of Financial Research , 2012, DOI: 10.5430/ijfr.v3n3p8
Abstract: In the past few years, the global automobile industry is developing difficultly because of the influence from the financial crisis. In contrast, China's automobile production and sales are still having a blowout type growth, and jumped into the world's largest automobile production and sales market. At the same time, Chinese automobile companies continue to deepen and join with international brand cooperation; independent research and development of the independent brand production, and their technical also get greatly strengthened. Similarly, in the tide of industrial upgrading and international acquisitions, strategic transformation era of Chinese automobile industry has gradually started. This paper based on the world economic crisis brought both challenge and opportunity to the automobile industry in China, comprehensively analysis China's automobile industry development present situation and development trend in the transformation era, with case analysis of China's automobile companies, and then gives some suggestions on China's automobile industry strategy adjustment in transformation.
H.W. Longfellow: A Poetical-Dwelling Poet of Ecological Wisdom from the Perspective of Eco-criticism
Jingcheng Xu,Meifang Nangong
English Language Teaching , 2012, DOI: 10.5539/elt.v5n5p85
Abstract: Among a minority of Longfellow’s studies in China and abroad, there has even scarcely been one made from the perspective of eco-criticism. Eco-criticism aims at exploring the relation between literature and natural environment to find out the ecological wisdom in literary works so as to awaken the ecological consciousness of the contemporaries. Henry Wadsworth Longfellow, a poet concerning much about nature, in his nature poems, shows the value of nature by evoking people’s love and care for nature, and makes them reconsider the Man-Nature relationship so as to seek the ecological balance on earth, including that from within the human world. By reading Longfellow in the light of certain eco-ethical ideas, it is not difficult to discover the legacy glittering with ecological wisdom in his poetry. Such wisdom is highly connected with Longfellow’s “environmental niche”. Nowadays, with the increasing deterioration of the environment, the ecological wisdom implied in Longfellow’s poetry is of tremendous significance.
Quantisation of a particle moving on a group manifold
Meifang Chu,Peter Goddard
Physics , 1994, DOI: 10.1016/0370-2693(94)90977-6
Abstract: The Hilbert space of a free massless particle moving on a group manifold is studied in details using canonical quantisation. While the simplest model is invariant under a global symmetry, $G \times G$, there is a very natural way to ``factorise" the theory so that only one copy of the global symmetry is preserved. In the case of $G=SU(2)$, a simple deformation of the quantised theory is proposed to give a realisation of the quantum group, $U_t(SL(2))$. The symplectic structures of the corresponding classical theory is derived. This can be used, in principle, to obtain a Lagrangian formulation for the $U_t(SL(2))$ symmetry.
Study on the Genetic Diversity of Osmanthus fragrans Cultivars
桂花品种资源的遗传多样性分析

Yuanji Han,Meifang Dong,Wangjun Yuan,Fude Shang,
韩远记
,董美芳,袁王俊,尚富德

植物学报 , 2008,
Abstract: We used morphological features and amplified fragment-length polymorphism (AFLP) markers to analyze the genetic diversity of 45 Osmanthus fragrans cultivars and found high levels of genetic diversity among the cultivars. Of the AFLP bands detected, 57.46% are polymorphic. We classified the cultivars biometrically according to their major morphological features and performed cluster analysis of the AFLP data by the unweighted pair-group method using arithmetic averages. The results of both approaches showed that O. fragrans cultivars of the Guilin region form a distinct subgroup, and flower color is aviable classification criterion. We discuss systems for O. fragrans cultivar classification.
Response of Nutrients in Apple Leaves to Regulation of Water and Fertilizers in Loess Hilly Area  [PDF]
Lei Hua, Jianen Gao, Meifang Zhou, Zhe Gao, Tingwu Lin
Open Journal of Soil Science (OJSS) , 2018, DOI: 10.4236/ojss.2018.84010
Abstract: Aiming at the problem of the low utilization ratio of water resource and fertilizers in apple orchard in loess hilly area, which is the result of both water shortage and improper fertilization, a field experiment of the regulation of water and fertilizers is carried out in a typical apple orchard in this area to make analysis of nutrients in apple leaves under different treatments of water and fertilizers. The results show that: in the experimental area: 1) the total nitrogen content in apple leaves maintains at a low level of 1.87% - 3.17%; the total phosphorus content in apple leaves maintains at a low or normal level of 0.13% - 0.16%; and the total potassium content in apple leaves maintains at a deficient level of 0.46% - 0.64%; 2) the regulation of water and fertilizers has some effect on promoting the trees to adsorb both the total nitrogen and the total potassium, but it has no apparent effect on promoting the leaves to adsorb the total phosphorus. In the management of water and fertilizers in this apple orchard, the effects of the water and the fertilizers should be properly regulated to make full use of the limited water resource and improve the utilization ratio of the fertilizers as well, so as to achieve the three goals of saving water, saving fertilizers and improving quality.
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