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Search Results: 1 - 10 of 81979 matches for " Xiaodong Liu "
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Effect of precession on the Asian summer monsoon evolution: A systematic review
XiaoDong Liu,ZhengGuo Shi
Chinese Science Bulletin , 2009, DOI: 10.1007/s11434-009-0540-5
Abstract: Geological climatic records and model simulations on the Asian summer monsoon climate change induced by insolation forcing of the Earth’s precession are systematically reviewed in this paper. The presentation of the questions on the mechanism of the Asian monsoon evolution at the precession band, currently existing debates and future research directions are discussed. Since the early 1980s, more and more observed evidence and simulated results, especially the absolute-dated stalagmite records and orbital-scale transient model runs in the last few years, have indicated that the quasi-20ka period in the Quaternary monsoon climate change is caused by precession. However, debates still exist on the dynamic mechanism how precession affects the Asian monsoon. The “zero phase” hypothesis says that the Asian monsoon is merely controlled by summer insolation in the Northern Hemisphere (NH) while the “latent heat” hypothesis emphasizes the dominant effect of latent heat transport from the Southern Hemisphere (SH) besides the role of the northern insolation. The two hypotheses have separately been supported by some evidence. Although we are cognizant of the importance of northern solar radiation and the remote effect of southern insolation, it has still a long way to go before comprehensively understanding the evolutionary mechanism of the Asian monsoon. In view of the problems existing in present researches of monsoon-dominated climate change at the precession scale, we propose that studies on the environmental significance of geological monsoon proxies, feedback processes in the long-term transient simulations and intercomparisons between observations and modeling results should be strengthened in the future.
Multiple-Symbol Decision-Feedback Space-Time Differential Decoding in Fading Channels
Liu Yan,Wang Xiaodong
EURASIP Journal on Advances in Signal Processing , 2002,
Abstract: Space-time differential coding (STDC) is an effective technique for exploiting transmitter diversity while it does not require the channel state information at the receiver. However, like conventional differential modulation schemes, it exhibits an error floor in fading channels. In this paper, we develop an STDC decoding technique based on multiple-symbol detection and decision-feedback, which makes use of the second-order statistic of the fading processes and has a very low computational complexity. This decoding method can significantly lower the error floor of the conventional STDC decoding algorithm, especially in fast fading channels. The application of the proposed multiple-symbol decision-feedback STDC decoding technique in orthogonal frequency-division multiplexing (OFDM) system is also discussed.
Inverse scattering by an inhomogeneous penetrable obstacle in a piecewise homogeneous medium
Xiaodong Liu,Bo Zhang
Mathematics , 2009,
Abstract: This paper is concerned with the inverse problem of scattering of time-harmonic acoustic waves by an inhomogeneous penetrable obstacle in a piecewise homogeneous medium. The well-posedness of the direct problem is first established by using the integral equation method. We then proceed to establish two tools that play an important role for the inverse problem: one is a mixed reciprocity relation and the other is a priori estimates of the solution on some part of the interfaces between the layered media. For the inverse problem, we prove in this paper that both the penetrable interfaces and the possible inside inhomogeneity can be uniquely determined from a knowledge of the far field pattern for incident plane waves.
Direct and inverse obstacle scattering problems in a piecewise homogeneous medium
xiaodong Liu,Bo Zhang
Mathematics , 2009,
Abstract: This paper is concerned with the problem of scattering of time-harmonic acoustic waves from an impenetrable obstacle in a piecewise homogeneous medium. The well-posedness of the direct problem is established, employing the integral equation method and then used, in conjunction with the representation in a combination of layer potentials of the solution, to prove a priori estimates of solutions on some part of the interface between the layered media. The inverse problem is also considered in this paper. An uniqueness result is obtained for the first time in determining both the penetrable interface and the impenetrable obstacle with its physical property from a knowledge of the far field pattern for incident plane waves. In doing so, an important role is played by the a priori estimates of the solution for the direct problem.
Information and Energy Cooperation in OFDM Relaying: Protocols and Optimization
Yuan Liu,Xiaodong Wang
Mathematics , 2015,
Abstract: Integrating power transfer into wireless communications for supporting simultaneous wireless information and power transfer (SWIPT) is a promising technique in energy-constrained wireless networks. While most existing work on SWIPT focuses on capacity-energy characterization, the benefits of cooperative transmission for SWIPT are much less investigated. In this paper, we consider SWIPT in an orthogonal frequency-division multiplexing (OFDM) relaying system, where a source node transfers information and a fraction of power simultaneously to a relay node, and the relay node uses the harvested power from the source node to forward the source information to the destination. To support the simultaneous information and energy cooperation, we first propose a transmission protocol assuming that the direct link between the source and destination does not exist, namely power splitting (PS) relaying protocol, where the relay node splits the received signal power in the first hop into two separate parts, one for information decoding and the other for energy harvesting. Then, we consider the case that the direct link between the source and destination is available, and the transmission mode adaptation (TMA) protocol is proposed, where the transmission can be completed by cooperative mode and direct mode simultaneously (over different subcarriers). In direct mode, when the source transmits signal to the destination, the destination receives the signal as information and the relay node concurrently receives the signal for energy harvesting. Joint resource allocation problems are formulated to maximize the system throughput. By using the Lagrangian dual method, we develop efficient algorithms to solve the nonconvex optimization problems.
Influence of Waste Materials Containing Tungsten on Melting and Crystallization of Glass-ceramics  [PDF]
Shaomin Lin, Bo Wang, Guishen Liu, Liqing Li, Xiaodong Hou
Advances in Materials Physics and Chemistry (AMPC) , 2012, DOI: 10.4236/ampc.2012.24B021
Abstract: Influences of waste materials containing tungsten on melting and crystallization of glass-ceramics are discussed in this article. High temperature melting, nucleation and crystallization of glass-ceramics were explored by means of DTA, XRD and SEM. The high temperature melting performance of glass-ceramics ingredients can be effectively improved by mixing the right amount of waste materials containing tungsten. But the additive amount should be properly controlled, the mixing content of waste materials containing tungsten should be a range of 0.5 ~ 2.0 %. In the experiment of glass-ceramics ingredients system, the molten softening temperature of base glass powder reduced about 20 ℃ by adding 1 % waste materials containing tungsten, and the nucleation temperature reduced about 15 ℃. The nucleation and crystallization performance of glass-ceramics mineral crystals can be promoted by mixing the right amount of waste materials containing tungsten. That is helpful to improve the quality of glass-ceramics products.
The Interaction between the Large-Scale EVs and the Power Grid  [PDF]
Yuan Huang, Junyong Liu, Xiaodong Shen, Tingting Dai
Smart Grid and Renewable Energy (SGRE) , 2013, DOI: 10.4236/sgre.2013.42017
Abstract:

With the problem of global energy shortage and peoples awareness of energy saving, electric vehicles receive world-wide attention from government to business. Then the load of the power grid will rapidly increase in a short term, and a series of effects will bring to the power grid operation, management, production and planning. With the large-scale penetration of electric vehicles and distributed energy gradually increased, if they can be effectively controlled and regulated, they can play the roles of load shifting, stabling intermittent renewable energy sources, providing emergency power supply and so on. Otherwise they may have a negative impact, which calls for a good interaction of electric vehicles and power grid. Analyzed the status of the current study on the interaction between the electric vehicles and the power grid, this paper builds the material basis, information architecture and the corresponding control method for the interaction from the aspect of the energy and information exchanging, and then discusses the key issues, which makes a useful exploration for the further research.

How Do the Nucleons Pack in an Atomic Nucleus?  [PDF]
Xiaodong Li, Qijun Liu, Gongyi Li, Yihe Li, Zengyong Chu
World Journal of Nuclear Science and Technology (WJNST) , 2014, DOI: 10.4236/wjnst.2014.44030
Abstract: A nuclear structure model of “ring plus extra nucleon” is proposed. For nuclei larger than 4He, protons (P) and neutrons (N) are basically bound alternatively to form a ZP + ZN ring. The ring folds with a “bond angle” of 90° for every 3 continuous nucleons to make the nucleons packed densely. Extra N(‘s) can bind to ring-P with the same “bond angle” and “bond distance”. When 2 or more P’s are geometrically available, the extra N tends to be stable. Extra P can bind with ring N in a similar way when the ratio of N/P < 1 although the binding is weaker than that of extra N. Even-Z rings, as well as normal even-even nuclei, always have superimposed gravity centers of P and N; while for odd-Z rings, as well as all odd-A (A: number of nucleon) nuclei, the centers of P and N must be eccentric. The eccentricity results in a depression of binding energy (EB) and therefore odd and even Z dependent zigzag features of EB/A. This can be well explained by the shift of eccentricity by extra nucleons. Symmetrical center may present in even-Z rings and normal even-even nuclei. While for odd-Z ring, only antisymmetric center (every P can find an N through the center and vice versa) is possible. Based on this model, a pair of mirror nuclei, PX+nNX and PXNX+n, should be equivalent in packing structure just like black-white photo and the negative film. Therefore, an identical spin and parity was confirmed for any pair. In addition, the EB/A difference of mirror nuclei pair is nearly a constant of 0.184n MeV. Many other facts can also be easily understood from this model, such as the neutron halo, the unusual stability sequence of 9Be, 7Be and 8Be and so on.
Tree Biomass Estimation in Central African Forests Using Allometric Models  [PDF]
Romeo Ekoungoulou, Donatien Nzala, Xiaodong Liu, Shukui Niu
Open Journal of Ecology (OJE) , 2018, DOI: 10.4236/oje.2018.83014
Abstract: Quantifying the tropical forests’ carbon stocks is presently an important component in the implementation of the emerging carbon credit market mechanisms. This calls for appropriate allometric equations predicting biomass which currently are scarce. In this study, we aimed to estimate above- and below-ground biomass and carbon stocks of trees, and to identify the variation in diameter-height allometry of Ipendja mixed terra firme lowland tropical forest’s trees. The study area is located at Ipendja forest management unit (UFA), close to Dongou district (Likouala Department), in Northern Republic of Congo. This study combined forest inventory data of 1340 trees recorded from eight studied plots distributed in two sites, respectively Mokelimwaekili (i.e., Old-growth forest) and Sombo (i.e., Selective logging forest). Trees measurements were done with rectangular plots, each 25 × 200 m (i.e., 0.5 ha, 5000 m2). In eight studied plots (4 plots per site), only trees with DBH 10 cm were measured and identified. 1340 trees founded were belonged 145 species and 36 botanical families (n = 733 and
Numerical study of aerosol effect on three types of clouds and precipitation in Beijing area

ZhiGuo Yue,XiaoDong Liu,ShuYan Liu,

寒旱区科学 , 2012,
Abstract:
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