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Search Results: 1 - 10 of 35275 matches for " Yi Meng "
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Trajectory Design and Optimization for LEO Satellites in Formation to Observe GEO Satellites’ Beams  [PDF]
Yi Lu, Yu Sun, Xiyun Hou, Yunhe Meng
International Journal of Astronomy and Astrophysics (IJAA) , 2018, DOI: 10.4236/ijaa.2018.84026
Abstract: This paper presents the methods and results for the trajectory design and optimization for the low earth orbit (LEO) satellites in formation to observe the geostationary orbit (GEO) satellites’ beams. The background of the trajectory design mission is the 9th China Trajectory Optimization Competition (CTOC9). The formation is designed according to the observation demands. The flying sequence is determined by a reference satellite using a proposed improved ephemeris matching method (IEMM). The formation is changed, maintained and transferred following the reference satellite employing a multi-impulse control method (MICM). Then the total observation value is computed by propagating the orbits of the satellites according to the sequence and transfer strategies. Based on the above methods, we have obtained a fourth prize in the CTOC9. The proposed methods are not only fit for this competition, but can also be used to fulfill the trajectory design missions for similar multi-object explorations.
Potential Hazard Map for Disaster Prevention Using GIS-Based Linear Combination Approach and Analytic Hierarchy Method  [PDF]
Szu-Hsien Peng, Meng-Ju Shieh, Shih-Yi Fan
Journal of Geographic Information System (JGIS) , 2012, DOI: 10.4236/jgis.2012.45046
Abstract: In recent years, global warming has gradually become obvious, thus created the climate change. Typhoon Morakot attacked Taiwan and brought heavy rainfall in August, 2009. In mountainous areas including Central and South Taiwan, the flood and debris flow disasters were induced by the typhoon. In this study, Changhua City is selected as the research region and the Delphi method is employed to interview experts and establish comprehensive evaluation criteria for assessing the evacuation plan on disaster areas. The concept is to combine the landslide potential analysis by geographic information systems with the flood or debris flow maps into the potential hazard map. Meanwhile, analytic hierarchy method (AHP) is comprehensively carried on the expert questionnaire survey for the potential hazard map of the compound disaster states. It should be useful for the local government and native people in the future.
Research and Application of Pollution Control in the Middle Reach of Ashe River by Multi-Objective Optimization  [PDF]
Yuanyuan Wang, Liang Guo, Yi Wang, Meng Ran, Jie Liu, Peng Wang
Journal of Geoscience and Environment Protection (GEP) , 2013, DOI: 10.4236/gep.2013.12001
Abstract: Based on one-dimensional water quality model and nonlinear programming, the point source pollution reduction model with multi-objective optimization has been established. To achieve cost effective and best water quality, for us to optimize the process, we set pollutant concentration and total amount control as constraints and put forward the optimal pollution reduction control strategy by simulating and optimizing water quality monitoring data from the target section. Integrated with scenario analysis, COD and ammonia nitrogen pollution optimization wasstudiedin objective function area from Mountain Maan of Acheng to Fuerjia Bridge along Ashe River. The results showed that COD and NH3-N contribution has been greatly reduced to AsheRiverby 49.6% and 32.7% respectively. Therefore, multi-objective optimization by nonlinear programming for water pollution control can make source sewage optimization fairly and reasonably, and the optimal strategies of pollution emission are presented.
Effect of Zn Substitution on the Magnetic and Magnetocapacitance Properties of Nanosized Multiferroic GaFeO3 Ceramics  [PDF]
Tai-Chun Han, Chun Yen, Yi-De Chung, Meng-Lin Wu
New Journal of Glass and Ceramics (NJGC) , 2018, DOI: 10.4236/njgc.2018.84005
Abstract: This article aims to investigate the possibility to turn the multiferroic orders and magnetocapacitance effect close to/above room temperature in nanosized GaFeO3 ceramics by a sol-gel preparation method and substitution with non-magnetic Zn atoms. Therefore, in this work, we have synthesized a series of nanocrystalline Ga1-xZnxFeO3(GZFO, x = 0, 0.01, 0.05 and 0.1) ceramic samples and study the effect of Zn substitution on their structural, magnetic, and electric properties. All the GZFO samples have an orthorhombic structure with Pc21n space group and the value of lattice parameters increase systematically with increasing Zn concentration. Interestingly, it shows that magnetic and electric properties are strongly dependent on the Zn substitution concentration. Based on the results of temperature-dependent magnetizations, M(T), it is observed that with increasing Zn-content up to 0.10, the ferrimagnetic transition temperature (TC) increases from 306 to 320 K. It is also found that the nanocrystalline Zn-doped GaFeO3 (GFO) samples exhibit the characteristics of ferroelectricity at room temperature. Furthermore, the?magnetization, ferroelectric polarization
Adaptive Regularized Level Set Method for Weak Boundary Object Segmentation
Meng Li,Chuanjiang He,Yi Zhan
Mathematical Problems in Engineering , 2012, DOI: 10.1155/2012/369472
Abstract: An adaptive regularized level set method for image segmentation is proposed. A weighted ()-Dirichlet integral is presented as a geometric regularization on zero level curve, which is used to diminish the influence of image noise on level set evolution while ensuring the active contours not to pass through weak object boundaries. The idea behind the new energy integral is that the amount of regularization on the zero level curve can be adjusted automatically by the variable exponent () to fit the image data. This energy is then incorporated into a level set formulation with an external energy term that drives the motion of the zero level set toward the desired objects boundaries, and a level set function regularization term that is necessary for maintaining stable level set evolution. The proposed model has been applied to a wide range of both real and synthetic images with promising results.
Link prediction based on a semi-local similarity index

Bai Meng,Hu Ke,Tang Yi,

中国物理 B , 2011,
Abstract: Missing link prediction provides significant instruction for both analysis of network structure and mining of unknown links in incomplete networks. Recently, many algorithms have been proposed based on various node-similarity measures. Among these measures, the common neighbour index, the resource allocation index, and the local path index, stemming from different source, have been proved to have relatively high accuracy and low computational effort. In this paper, we propose a similarity index by combining the resource allocation index and the local path index. Simulation results on six unweighted networks show that the accuracy of the proposed index is higher than that of the local path one. Based on the same idea of the present index, we develop its corresponding weighted version and test it on several weighted networks. It is found that, except for the USAir network, the weighted variant also performs better than both the weighted resource allocation index and the weighted local path index. Due to the improved accuracy and the still low computational complexity, the indices may be useful for link prediction.
The Forecasting Power of the Volatility Index in Emerging Markets: Evidence from the Taiwan Stock Market
Ming Jing Yang,Meng-Yi Liu
International Journal of Economics and Finance , 2012, DOI: 10.5539/ijef.v4n2p217
Abstract: This paper explores the predictive power of the volatility index (VIX) in emerging markets from December 2006 to March 2010. The results of the study show that the models including both the volatility indicator and the option market information have a stronger predictive power. The predictive power of the models is improved by 88% in explaining the future volatility of stock markets, much better than that of other models merely considering the volatility indicator. With respect to the trading information from different types of investors in option markets, the trading information from the foreign institutional investors in option markets demonstrates a significantly positive relationship with the stock market volatility. In addition, the results of this paper also reveal that the volatility index (TVIX) of Taiwan stock index options is a strong indicator of future stock market volatility. The TVIX outperforms the historical volatility and the GARCH volatility forecast in assessing the activities of Taiwan’s stock market.
Effect of Mn on microstructures and mechanical properties of Al-Mg-Si-Cu-Cr-V alloy
Zhao Zhihao,Meng Yi,Cui Jianzhong
China Foundry , 2012,
Abstract: In order to improve the performances of the Al-Mg-Si-Cu-Cr-V alloy, various amounts of Mn (0-0.9wt.%) were added. The effect of this Mn on the microstructures and mechanical properties of Al-Mg-Si-Cu-Cr-V alloys in different states, especially after hot extrution and solid solution treatment, was systematically studied using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and mechanical tests at room temperature. The results show that 0.2wt.% Mn can both refine the as-cast microstructure of the alloy and strengthen the extrusion+T6 state alloy without damaging the plasticity badly due to the formation of Al15(FeMn)3Si2 and Al15Mn3Si2 dispersoids. Compared with the extrusion+T6 state alloy without Mn addition, the ultimate tensile strength and yield strength of the alloy with 0.2wt.% Mn addition are increased from 416.9 MPa to 431.4 MPa, 360.8 MPa to 372 MPa, respectively. The elongation of the extrusion+T6 state alloy does not show obvious change when the Mn addition is less than 0.5wt.%, and for the alloy with 0.2wt.% Mn addition its elongation is still as high as 15.6%. However, when over 0.7wt.% Mn is added to the alloy, some coarse, stable and refractory AlVMn and Al(VMn)Si phases form. These coarse phases can reduce the effect of Mn on the inhibition of re-crystallization; and they retain the angular morphology permanently after the subsequent deformation process and heat treatment. This damages the mechanical properties of the alloy.
Measuring Modular Matrices by Shearing Lattices
Yi-Zhuang You,Meng Cheng
Physics , 2015,
Abstract: A topologically ordered phase on a torus possesses degenerate ground states that transform nontrivially under the modular transformations of the torus, generated by Dehn twists. Representation of modular transformations on the ground states (modular matrices) characterizes the topological order. We show that the modular matrices can be numerically measured as the non-Abelian Berry phase of adiabatic deformations of the lattice model placed on a torus. We apply this method to the example of a gauged $p_x+i p_y$ superconductor, and show that the result is consistent with the topological quantum field theory descriptions.
Label-Guided Graph Exploration with Adjustable Ratio of Labels
Meng Zhang,Yi Zhang,Jijun Tang
Computer Science , 2012,
Abstract: The graph exploration problem is to visit all the nodes of a connected graph by a mobile entity, e.g., a robot. The robot has no a priori knowledge of the topology of the graph or of its size. Cohen et al. \cite{Ilcinkas08} introduced label guided graph exploration which allows the system designer to add short labels to the graph nodes in a preprocessing stage; these labels can guide the robot in the exploration of the graph. In this paper, we address the problem of adjustable 1-bit label guided graph exploration. We focus on the labeling schemes that not only enable a robot to explore the graph but also allow the system designer to adjust the ratio of the number of different labels. This flexibility is necessary when maintaining different labels may have different costs or when the ratio is pre-specified. We present 1-bit labeling (two colors, namely black and white) schemes for this problem along with a labeling algorithm for generating the required labels. Given an $n$-node graph and a rational number $\rho$, we can design a 1-bit labeling scheme such that $n/b\geq \rho$ where $b$ is the number of nodes labeled black. The robot uses $O(\rho\log\Delta)$ bits of memory for exploring all graphs of maximum degree $\Delta$. The exploration is completed in time $O(n\Delta^{\frac{16\rho+7}{3}}/\rho+\Delta^{\frac{40\rho+10}{3}})$. Moreover, our labeling scheme can work on graphs containing loops and multiple edges, while that of Cohen et al. focuses on simple graphs.
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