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Search Results: 1 - 10 of 29063 matches for " Yuanyuan Sun "
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First Principles DFT Study of Hydrogen Storage on Graphene with La Decoration  [PDF]
Yuanyuan Li, Yiming Mi, Gaili Sun
Journal of Materials Science and Chemical Engineering (MSCE) , 2015, DOI: 10.4236/msce.2015.312013
Abstract: The properties of hydrogen storage on graphene with La decoration are investigated using a first-principles plane-wave pseudopotential method based on the density functional theory in this paper. The clustering problem of La decorated graphene is considered and B doping can solve it effectively in theory. We obtain the stable geometrical configuration of the modified system and the properties of hydrogen storage are excellent. It can absorb up to 6 H2 molecules with an average adsorption energy range of?0.529 to 0.655 eV/H2, which meets the ideal range between the physisorbed and chemisorbed states for hydrogen storage. Furthermore, it is proved that the existence of La atom alters the charge distribution of H2 molecules and graphene sheet based on the calculation and analysis about the electronic density of states and charge density difference of the modified system. La atom interacts with hydrogen molecules through Kubas interaction. Thereby, it improves the performance of graphene sheet for hydrogen storage. The modified system exhibits the excellent potential to become one of the most suitable candidates for hydrogen storage medium at near ambient conditions with molecule state.
The Structures and Properties of Y-Substituted Mg2Ni Alloys and Their Hydrides: A First-Principles Study  [PDF]
Yuanyuan Li, Gaili Sun, Yiming Mi
American Journal of Analytical Chemistry (AJAC) , 2016, DOI: 10.4236/ajac.2016.71007
Abstract: The structures and properties of Y-substituted Mg2Ni alloys and the corresponding hydrides are investigated by a first-principles plane-wave pseudopotential method within density functional theory. Results show that Mg2Ni has the best structural stability when Y atom occupies the Mg(6f) lattice sites. The calculated enthalpies of formation for Mg2Ni, Mg2NiH4 and Mg15YNi8H32 are -51.612, -64.667 and -62.554 kJ/mol, respectively. It is implied that the substitution of Y alloying destabilizes the stability of the hydrides. Moreover, the dissociated energies of H atoms are decreased significantly, indicating that Y alloying benefits the improvement of the dehydrogenating properties of Mg2Ni hydrides. The calculation and analysis of the electronic structures suggest that there is a stronger interaction between H and Ni atoms than the interaction between H and Mg atoms in Mg2NiH4. However, the Ni-H bond is weakened by the substitution of Y. Therefore, the substitution is an effective technique to decrease the structural stability of the hydrides and benefit for hydrogen storage.
State Feedback Stabilization of Discrete Singular Large-scale Control Systems
Shuiling SUN,Yuanyuan CHEN
Studies in Mathematical Sciences , 2011,
Abstract: : This paper studies the state feedback stabilization of discrete singular large-scale control systems by using Lyapunov matrix equation, generalized Lyapunov function method and matrix theory. There gives some sufficient conditions for determining the asymptotical stability and instability of the corresponding singular closed-loop large-scale systems while the subsystems are regular, causal and R-controllable. At last, an example is given to show the application of main result. Key words: Discrete Singular Large-Scale Control System; Asymptotical Stability; Stabilization; Generalized Lyapunov Function; State Feedback
First-Principles Investigation of the Effect of M-Doped (M = Zr, Hf) TiCoSb Half-Heusler Thermoelectric Material  [PDF]
Gaili Sun, Yuanyuan Li, Xinxin Zhao, Yiming Mi, Lili Wang
Journal of Materials Science and Chemical Engineering (MSCE) , 2015, DOI: 10.4236/msce.2015.312012
Abstract: The M-doping (M = Zr, Hf) effects on the electronic structures and thermoelectric performance of TiCoSb were studied by first-principles calculations. The band structure analysis shows that substituting Ti with M does not change the band structures of these systems significantly. Most of the M-doped systems have a lower band gap value than that of TiCoSb; especially Ti0.5Zr0.5CoSb has the lowest energy band gap value of 0.971 eV. Besides, the amplitudes of the density of states in the region of the valence bands for M-doped systems show a similar but slightly higher value than TiCoSb. Those suggest that these compounds could have better thermoelectric performance than TiCoSb. The phonon dispersion relations show that the larger mass of Zr/Hf with respect to Ti lowers the optical modes and induces mixing with the acoustic branches. Our calculations offer a valuable insight on how to characterize complicated crystal structures of thermoelectric materials and optimize the material composition.
First-Principles Investigation of Energetics and Electronic Structures of Ni and Sc Co-Doped MgH2  [PDF]
Gaili Sun, Yuanyuan Li, Xinxin Zhao, Yiming Mi, Lili Wang
American Journal of Analytical Chemistry (AJAC) , 2016, DOI: 10.4236/ajac.2016.71004
Abstract: First-principles calculations were used to study the energetics and electronic structures of Ni and Sc co-doped MgH2 system. The preferential positions for dopants were determined by the minimal total electronic energy. The results of formation enthalpy indicate that Ni and Sc co-doped MgH2 system is more stable than Ni single-doped system. The hydrogen desorption enthalpies of these two hydrides are investigated. Ni and Sc co-doping can improve the dehydrogenation properties of MgH2. The lowest hydrogen desorption enthalpy of 0.30 eV appears in co-doped system, which is significantly lower than that of Ni doping. The electronic structure analysis illustrates that the hybridization of dopants with Mg and H atom together weakens the Mg-H interaction. And the Mg-H bonds are more susceptible to dissociate by Ni and Sc co-doping because of the reduced magnitude of Mg-H hybridization peaks. These behaviors effectively improve the dehydrogenation properties of Ni and Sc co-doped cases.
The Generalized Julia Set Perturbed by Composing Additive and Multiplicative Noises
Xingyuan Wang,Ruihong Jia,Yuanyuan Sun
Discrete Dynamics in Nature and Society , 2009, DOI: 10.1155/2009/781976
Abstract: This paper contrastively researches the structural characteristic and the fission-evolution law of four different kinds of generalized Julia set (generalized J set in short) with different parameter , which includes the generalized J set without any perturbation, the generalized J set perturbed by additive noises, the generalized J set perturbed by multiplicative noise, and the generalized J set perturbed by composing additive and multiplicative noises, analyzes the effect of random perturbation to the generalized J set, and illuminates the stability of the generalized J set.
Accurate Computation of Periodic Regions' Centers in the General M-Set with Integer Index Number
Wang Xingyuan,He Yijie,Sun Yuanyuan
Discrete Dynamics in Nature and Society , 2010, DOI: 10.1155/2010/653816
Abstract: This paper presents two methods for accurately computing the periodic regions' centers. One method fits for the general M-sets with integer index number, the other fits for the general M-sets with negative integer index number. Both methods improve the precision of computation by transforming the polynomial equations which determine the periodic regions' centers. We primarily discuss the general M-sets with negative integer index, and analyze the relationship between the number of periodic regions' centers on the principal symmetric axis and in the principal symmetric interior. We can get the centers' coordinates with at least 48 significant digits after the decimal point in both real and imaginary parts by applying the Newton's method to the transformed polynomial equation which determine the periodic regions' centers. In this paper, we list some centers' coordinates of general M-sets' -periodic regions for the index numbers , all of which have highly numerical accuracy. 1. Introduction According to the idea of complex dynamic system theory presented by Julia and Fatou, the famous mathematician Mandelbrot constructed and studied the M-sets of complex mapping utilizing computer graphics technologies [1]. During the last 20 years, people have researched the embedded-layer relationship and distribution of the bifurcation sequence and topological rule of periodic trajectories in the general M-sets with and found there existed orderly structure within the M-sets [2–16]. For example, álvarez et al. studied the location and number of each periodic region in M-sets [9]; Buchanan et al. studied the location of periodic region of the general M-sets with [11]; Geum and Kim analyzed the quantitative relationship of each periodic region in the general Mandelbrot sets with positive integer index number, and calculated the coordinates of periodic regions’ centers [15]; The author studied the structure and distribution of the general M-sets with integer index number [16]. M-sets consist of different-period regions which constitute the fractal structures of the M-sets. The analysis on the stability of the maps uncovered new and unexpected algebraic properties of the periodic regions. The centers of the periodic regions are determined by the transformed polynomials we worked on. The motivation for computing the periodic regions’ centers is provided by the need to consider the locations of the periodic regions and fractal structures of the M-sets, which are useful to understand the inner infinite structures of the M-sets. On the basis of above research, we study the
Empirical Study on the Factors Influencing the Willingness of Pig-breeding farms and Farmers to Keep Breeding Record
Zhaomin XIA,Shimin SUN,Yuanyuan ZHANG
Management Science and Engineering , 2011, DOI: 10.3968/j.mse.1913035x20110503.4z375
Abstract: Establishment of pig-breeding record is fundamental to enforce the source supervision of pork production and construct the tracing mechanism of pork quality safety. Based on the result of 327 questionnaires, Logit Binary Choice Model is used in this paper to quantitatively analyze the factors influencing the willingness of pigbreeding farms and farmers to establish breeding record. It shows that six factors, which are education level, specialized level, participation in pig-breeding cooperative organization, recognition of breeding record, government’s propaganda and supervision, have significant and positive impact on the willingness of pigbreeding farms and farmers to build breeding record. Key words: Pig-breeding farm and farmer; Breeding record; Logit model; Influence factors
The Equality of Distribution of Education Resources—The Case of 96 Universities in the US  [PDF]
Yuanyuan Liu
Open Journal of Social Sciences (JSS) , 2017, DOI: 10.4236/jss.2017.51014
Abstract: This study uses Gini coefficient and the different decomposition of Gini coefficient to investigate the equality of distribution of human capital and endowment. The result shows that neither the amount of endowment nor the number of teachers indeed causes a great deal of inequality in different schools. The contribution from full-time teachers is more than the contribution from the part-time teachers to the inequal distribution of teachers. For the inequal distribution of endowment, the contribution from the between-group is greater than the contribution from with-group.
Post Disaster Community Recovery
—Case Study: 2008 Hurricane Ike in the United States vs 2015 Caihong Typhoon in China

Yuanyuan Tang
Open Journal of Social Sciences (JSS) , 2017, DOI: 10.4236/jss.2017.51009
Abstract: Disaster happens frequently these years. Both America and China suffer all kinds of disasters. Many researches have been done to study the four stages of disaster: Mitigation, Preparedness, Response, and Recovery. But few researches are about the community recovery plan in these two countries. This study is based on case study about 2008 Hurricane Ike in Galveston, Texas and 2015 Typhoon Caihong in Zhanjiang, Guangdong. By comparing the difference between the recovery plan process, the results suggest that recovery plan process shows the way of “from bottom to top” in America and “from top to bottom” in China. And the civil participation is much deeper in America.
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