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Search Results: 1 - 10 of 360965 matches for " S. Yan "
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Dust Suppression with Glycerin from Biodiesel Production: A Review  [PDF]
Wei Yan, S. Kent Hoekman
Journal of Environmental Protection (JEP) , 2012, DOI: 10.4236/jep.2012.32027
Abstract: An increasing number of countries and areas in the world suffer from either natural or anthropogenic dust, which results in a serious hazard with respect to the environment and to personal health and safety. This paper reviews and summa- rizes open literature involving the use of glycerin in dust control applications. Glycerin, a by-product from biodiesel manufacturing, has been evaluated for dust suppressant performance when applied alone as aqueous solutions, or in combinations with surfactants, polymers, or other chemicals. There are reports indicating that glycerin is effective in some dust suppression applications, although details about its use and performance metrics are generally lacking. Re- cent growth of the biodiesel industry has significantly increased the supply of crude glycerin, making it an economically attractive material for use in dust suppression. This paper also highlights several environmental accidents caused by irresponsible discharges of crude glycerin, and points out the need to understand environmental consequences of gly- cerin and its impurities when used in dust suppression applications.
Density matrix renormalization group study of conjugated polymers with transverse pi-conjugation
Y. Yan,S. Mazumdar
Physics , 2005, DOI: 10.1103/PhysRevB.72.212201
Abstract: We report accurate numerical studies of excited state orderings in long hypothetical pi-conjugated oligomers in which the hydrogen atoms of trans-polyacetylene are replaced with conjugated sidegroups, within modified Hubbard models. There exists a range of the bare Coulomb repulsion for which the excited state ordering is conducive to photoluminescence in the substituted systems, even as this ordering is opposite in the unsubstituted polyenes of the same lengths. Our work provides motivation to study real pi-conjugated polymers with transverse conjugation and small optical gaps.
States of Local Moment Induced by Nonmagnetic Impurities in Cuprate Superconductors
Yan Chen,C. S. Ting
Physics , 2003, DOI: 10.1103/PhysRevLett.92.077203
Abstract: By using a model Hamiltonian with d-wave superconductivity and competing antiferromagnetic (AF) orders, the local staggered magnetization distribution due to nonmagnetic impurities in cuprate superconductors is investigated. From this, the net magnetic moment induced by a single or double impurities can be obtained. We show that the net moment induced by a single impurity corresponds to a local spin with S_z=0, or 1/2 depending on the strength of the AF interaction and the impurity scattering. When two impurities are placed at the nearest neighboring sites, the net moment is always zero. For two unitary impurities at the next nearest neighboring sites, and at sites separated by a Cu-ion site, the induced net moment has S_z=0, or 1/2, or 1. The consequence of these results on experiments will be discussed.
Flare and CME Properties and Rates at Sunspot Minimum
Hugh S. Hudson,Yan Li
Physics , 2010,
Abstract: The corona at solar minimum generally differs greatly from that during active times. We discuss the current Cycle 23/24 minimum from the point of view of the occurrence of flares and CMEs (Coronal Mass Ejections). By comparison with the previous minimum, the flare/CME ratio diminished by almost an order of magnitude. This suggests that the environmental effect in flare/CME association differed in the sense that the Cycle 23/24 minimum corona was relatively easy to disrupt.
Correlated charged impurity scattering in graphene
Jun Yan,Michael S. Fuhrer
Physics , 2011, DOI: 10.1103/PhysRevLett.107.206601
Abstract: Understanding disorder in graphene is essential for electronic applications; in contrast to conventional materials, the extraordinarily low electron-phonon scattering1, 2 in graphene implies that disorder3-7 dominates its resistivity even at room temperature. Charged impurities5, 8-10 have been identified as an important disorder type in graphene on SiO2 substrates11, 12, giving a nearly linear carrier-density-dependent conductivity {\sigma}(n), and producing electron and hole puddles13-15 which determine the magnitude of graphene's minimum conductivity {\sigma}min10. Correlations of charged impurities are known to be essential in achieving the highest mobilities in remotely-doped semiconductor heterostructures16-18, and are present to some degree in any impurity system at finite temperature. Here we show that even modest correlations in the position of charged impurities, realized by annealing potassium on graphene, can increase the mobility by more than a factor of four. The results are well understood theoretically19 considering an impurity correlation length which is temperature dependent but independent of impurity density. Impurity correlations also naturally explain the sub-linear {\sigma}(n) commonly observed in substrate-bound graphene devices2, 11, 12, 20.
Theory of Magnetic Field Induced Spin Density Wave in High Temperature Superconductors
Yan Chen,C. S. Ting
Physics , 2001, DOI: 10.1103/PhysRevB.65.180513
Abstract: The induction of spin density wave (SDW) and charge density wave (CDW) orderings in the mixed state of high $T_c$ superconductors (HTS) is investigated by using the self-consistent Bogoliubov-de Gennes equations based upon an effective model Hamiltonian with competing SDW and d-wave superconductivity interactions. For optimized doping sample, the modulation of the induced SDW and its associated CDW is determined by the vortex lattice and their patterns obey the four-fold symmetry. By deceasing doping level, both SDW and CDW show quasi-one dimensional like behavior, and the CDW has a period just half that of the SDW along one direction. From the calculation of the local density of states (LDOS), we found that the majority of the quasi-particles inside the vortex core are localized. All these results are consistent with several recent experiments on HTS.
Charge transport in dual gated bilayer graphene with Corbino geometry
Jun Yan,Michael S. Fuhrer
Physics , 2010, DOI: 10.1021/nl102459t
Abstract: The resistance of dual-gated bilayer graphene is measured as a function of temperature and gating electric fields in the Corbino geometry which precludes edge transport. The temperature-dependent resistance is quantitatively described by a two channel conductance model including parallel thermal activation and variable range hopping channels, which gives the electric-field-dependent band gap whose magnitude is found to be in good agreement with infrared absorption experiments. Low temperature transport is similar to previous studies of dual-gated bilayer graphene with edges, suggesting that edge transport does not play an important role.
Dimerization-induced enhancement of the spin gap in the quarter-filled two-leg rectangular ladder
Y. Yan,S. Mazumdar,S. Ramasesha
Physics , 2006, DOI: 10.1103/PhysRevB.73.224418
Abstract: We report density-matrix renormalization group calculations of spin gaps in the quarter-filled correlated two-leg rectangular ladder with bond-dimerization along the legs of the ladder. In the small rung-coupling region, dimerization along the leg bonds can lead to large enhancement of the spin gap. Electron-electron interactions further enhance the spin gap, which is nonzero for all values of the rung electron hopping and for arbitrarily small bond-dimerization. Very large spin gaps, as are found experimentally in quarter-filled band organic charge-transfer solids with coupled pairs of quasi-one-dimensional stacks, however, occur within the model only for large dimerization and rung electron hopping that are nearly equal to the hopping along the legs. Coexistence of charge order and spin gap is also possible within the model for not too large intersite Coulomb interaction.
Membrane skeleton spectrin in pollen and pollen tube
Yan Li,Longfei Yan,S. Y. Zee,B. Q. Huang
Chinese Science Bulletin , 1999, DOI: 10.1007/BF02885068
Abstract: Immuno-western blots, immunofluorescence and immuno-gold labeling methods were used to study the existence and distribution of a homologue of the membrane skeleton spectrin in the pollen and pollen tube ofLilium davidii Duch. A spectrin homologue was found to exist in the pollen and pollen tube, distributed on membranes of secretory vesicles near Golgi apparatus.
Functional design method for improving safety and ergonomics of mechanical products  [PDF]
Aurélie Robert, Sébastien Roth, Dominique Chamoret, Xiu Tian Yan, Francois Peyraut, Samuel Gomes
Journal of Biomedical Science and Engineering (JBiSE) , 2012, DOI: 10.4236/jbise.2012.58058
Abstract: In order to help companies to improve their competetiveness, it is important to develop new design methodologies. In this framework, a Functional And Robust Design (FARD) methodology dedicated to routine design of “highly productive” modular product ranges is proposed including principles of functional analysis, Design For Assembly (DFA), and techniques of modelling and simulation for ergonomics consideration. This paper focuses on the application of this original method applied to mechanical vibration and ergonomics problems of a scraper. Including biomechanical aspect in the design methodology, it is possible to identify the impact of a vibration tool on its users using numerical models of the tool coupled to a finite element model of the human hand. This method can proactively warn very early, in the design process, the risks of causing musculoskeletal disorders and facilitate an optimization of the mechanical tool. This study is a first step in a context of human-centered design.
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