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Search Results: 1 - 10 of 13746 matches for " Liqiang Fan "
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Coordinated Control of Traffic Signals for Multiple Intersections  [PDF]
Liqiang Fan
Applied Mathematics (AM) , 2014, DOI: 10.4236/am.2014.513197
Abstract: The proper phase difference of traffic signals for adjacent intersections could decrease the time of operational delay. Some theorems show how to minimize the total average delay time for vehicle operating at adjacent intersections under given conditions. If the distance and signal cycles of adjacent intersections satisfy with specific conditions, the total average delay time would achieve zero. If the signal cycles of adjacent intersections and the phase difference of them are co-prime numbers, the total average delay time would be a constant. In general, if signal cycles of adjacent intersections and the phase difference of them are reducible numbers, the minimum total average delay time would be solved by the given algorithm. Numerical experiments have verified the rationality of these theorems.
K-Nearest Neighbor Based Missing Data Estimation Algorithm in Wireless Sensor Networks  [PDF]
Liqiang Pan, Jianzhong Li
Wireless Sensor Network (WSN) , 2010, DOI: 10.4236/wsn.2010.22016
Abstract: In wireless sensor networks, the missing of sensor data is inevitable due to the inherent characteristic of wireless sensor networks, and it causes many difficulties in various applications. To solve the problem, the missing data should be estimated as accurately as possible. In this paper, a k-nearest neighbor based missing data estimation algorithm is proposed based on the temporal and spatial correlation of sensor data. It adopts the linear regression model to describe the spatial correlation of sensor data among different sensor nodes, and utilizes the data information of multiple neighbor nodes to estimate the missing data jointly rather than independently, so that a stable and reliable estimation performance can be achieved. Experimental results on two real-world datasets show that the proposed algorithm can estimate the missing data accurately.
Three-Dimensional Nanoporous Graphene Substrate for Surface-Enhanced Raman Scattering
Zhiqiang Tu,Shangfei Wu,Fan Yang,Yongfeng Li,Liqiang Zhang,Hongwen Liu,Hong Ding,Pierre Richard
Physics , 2014, DOI: 10.1016/j.matlet.2015.03.131
Abstract: We synthesized three-dimensional nanoporous graphene films by a chemical vapor deposition method with nanoporous copper as a catalytic substrate. The resulting nanoporous graphene has the same average pore size as the underlying copper substrate. Our surface-enhanced Raman scattering (SERS) investigation indicates that the nanoporosity of graphene significantly improves the SERS efficiency of graphene as a substrate as compared to planar graphene substrates.
Tribromomelamine: A Novel and Efficient Catalyst for the Synthesis 2-Arylthiazolines under Solvent-free Conditions
Liqiang Wu
Journal of Chemistry , 2012, DOI: 10.1155/2012/972109
Abstract: A novel procedure for the synthesis of 2-arylthiazolines through one-pot condensation of of nitriles with 2-aminoethanethiol in the presence of tribromomelamine as catalyst under solvent-free conditions is described.
Zr(HSO4)4: An Efficient Catalyst for the Synthesis of 3-(2'- Benzothiazolyl)-2,3-dihydroquinazolin- 4(1H)-ones
Liqiang Wu
Journal of Chemistry , 2012, DOI: 10.1155/2012/515029
Abstract: A simple and efficient synthesis of 3-(2'-benzothiazolyl)-2,3-dihydro quinazolin-4(1H)- ones has been accomplished by the one-pot condensation of isatoic anhydride, aldehyde and 2-aminobenzothiazole under solvent-free conditions in the presence of Zr(HSO4)4.
Exploring Harmony between Theory and Computation - Toward a unified electronic structure theory
Liqiang Wei
Physics , 2006,
Abstract: The physical aspect of a general perturbation theory is explored. Its role as a physical principle for understanding the interaction among matter with different levels of hierarchy is appreciated. It is shown that the generic perturbation theory can not only be used for understanding various electronic phenomena including the nature of chemical bonds but also serve as a $\it{unified}$ theme for developing $\it{general}$ electronic structure theories and calculation schemes. In particular, a $\it{standard}$ electron correlation approach is suggested and established according to this law.
Exploring the Harmony between Theory and Computation - Toward a unified electronic structure theory
Liqiang Wei
Physics , 2003,
Abstract: The physical aspect of a general perturbation theory is explored. Its role as a physical principle for understanding the interaction among the matters with different levels of hierarchy is appreciated. It is shown that the general perturbation theory can not only be used for understanding the various electronic phenomena including the nature of chemical bonds but also serve as a unified theme for constructing general electronic structure theories and calculation schemes.
On Emerging Fields of Quantum Chemistry at Finite Temperature
Liqiang Wei
Physics , 2004,
Abstract: In this article, we present an emerging field of quantum chemistry at finite temperature. We discuss its recent developments on both theoretical and experimental fronts.We describe and analyze several experimental investigations related to the temperature effects on the structure, electronic spectra,or bond rupture forces for molecules. This includes the study of the temperature impact on the pathway shifts for the protein unfolding by atomic force microscopy, the temperature dependence of the absorption spectra of electrons in solvents, and temperature influence over the intermolecular forces measured by the AFM. On the theoretical side, we review a recent advancement made by the author in the coming fields of quantum chemistry at finite temperature. Starting from Bloch equation, we have derived the sets of hierarchy equations for the reduced density operators in both canonical and grand canonical ensembles. They provide a law according to which the reduced density operators vary in temperature for the identical and interacting many-body particles. By taking the independent particle approximation, we have solved the equation in the case of a grand canonical ensemble, and obtained an eigenequation for the molecular orbitals at finite temperature. The explicit expression for the temperature-dependent Fock operator is also given. They will form a foundation for the study of the molecular electronic structures and their interplay with the finite temperature. Furthermore, we clarify the physics concerning the temperature effect on the electronic structure or processes of molecules which is crucial for both theoretical understanding and computational study.Finally,we summarize our discussion and point out the theoretical and computational issues for the future explorations in the fields of quantum chemistry at finite temperature.
Single-Particle Green Function Approach and Correlated Atomic or Molecular Orbitals
Liqiang Wei
Physics , 2004,
Abstract: In this paper, we propose a generic and systematic approach for study of the electronic structure for atoms or molecules. In particular, we address the issue of single particle states, or orbitals, which should be one of the most important aspects of a quantum many-body theory. We argue that the single-particle $\it{Green}$ function provides a most general scheme for generating these single particle states or orbitals. We call them the $\it{correlated}$ atomic or molecular orbitals to make a distinction from those determined from $\it{Hartree-Fock}$ equation. We present the calculation of the single particle properties (i.e., the electron affinities $(EA's)$ and ionization potentials $(IP's)$) for the $H_{2}O$ molecule using the correlated molecular orbitals in the context of quantum chemistry with a second-order self energy. We also calculate the total ground state energy with a single $Slater$ wavefunction determined only from the hole states. Comparisons are made with available experimental data as well as with those from the $\it{Hartree-Fock}$ or density functional theory $(DFT)$ calculations. We conclude that the correlated atomic or molecular orbital approach provides a strictest and most powerful method for studying the single-particle properties of atoms or molecules. It also gives a better total energy than do the $\it{Hartree-Fock}$ and $\it{DFT}$ even at the single $\it{Slater}$ determinant level. It promises that a correlation theory based on the correlated atomic or molecular orbitals will become an approach which possesses the advantages and also overcomes their shortcomings of current quantum chemistry methods based on either the conventional quantum many-body theory or the $DFT$.
Quantum Chemistry at Finite Temperature
Liqiang Wei
Physics , 2006,
Abstract: In this article, we present emerging fields of quantum chemistry at finite temperature. We discuss its recent developments on both experimental and theoretical fronts. First, we describe several experimental investigations related to the temperature effects on the structures, electronic spectra, or bond rupture forces for molecules. These include the analysis of the temperature impact on the pathway shifts for the protein unfolding by atomic force microscopy (AFM), the temperature dependence of the absorption spectra of electrons in solvents, and the temperature influence over the intermolecular forces measured by the AFM. On the theoretical side, we review advancements made by the author in the coming fields of quantum chemistry at finite temperature. Starting from the Bloch equation, we have derived the sets of hierarchy equations for the reduced density operators in both canonical and grand canonical ensembles. They provide a law according to which the reduced density operators vary in temperature for the identical and interacting many-body systems. By taking the independent particle approximation, we have solved the equations in the case of a grand canonical ensemble, and obtained an energy eigenequation for the molecular orbitals at finite temperature. The explicit expression for the temperature-dependent Fock operator is also given. They form a mathematical foundation for the examination of the molecular electronic structures and their interplay with finite temperature. Moreover, we clarify the physics concerning the temperature effects on the electronic structures or processes of the molecules, which is crucial for both theoretical understanding and computation. Finally, ....
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