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Search Results: 1 - 10 of 291569 matches for " K. Y. Wang "
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THz Oscillations in a GaN Based Planar Nano-Device  [PDF]
K. Y. Xu, Y. N. Wang, Z. N. Wang, J. W. Xiong, G. Wang
Journal of Computer and Communications (JCC) , 2013, DOI: 10.4236/jcc.2013.17012
Abstract:

Gunn oscillations in a GaN based planar nano-device have been studied by ensemble Monte Carlo (EMC) method. Simulation results show that when the channel length of the device reduces to 450 nm, THz oscillations (about 0.3 THz) can be obtained. Also the phase of the oscillations can be controlled by the initial conditions that excite the Gunn domains. Moreover, through adjusting the phase difference between the oscillations in a double-channels device, which attained by parallel connecting two single-channel devices, the frequency of the device shifts from 0.3 THz to 0.6 THz. This phenomenon remains in devices with shorter channel-length, unless the channel-length is too short to support Gunn oscillations. The possible underlying mechanisms are also discussed.

Robust half-metallic antiferromagnets La$A$VOsO$_6$ and La$A$Mo$Y$O$_6$ ($A$ = Ca, Sr, Ba; $Y$ = Re, Tc) from first-principles calculations
Y. K. Wang,G. Y. Guo
Physics , 2006, DOI: 10.1103/PhysRevB.73.064424
Abstract: We have theoretically designed three families of the half-metallic (HM) antiferromagnets (AFM), namely, La$A$VOsO$_6$, La$A$MoTcO$_6$ and La$A$MoReO$_6$ ($A$ = Ca, Sr, Ba), based on a systematic {\it ab initio} study of the ordered double perovskites La$ABB'$O$_6$ with the possible $B$ and $B'$ pairs from all the 3$d$, 4$d$ and 5$d$ transtion metal elements being considered. Electronic structure calculations based on first-principles density-functional theory with generalized gradient approximation (GGA) for more than sixty double perovskites LaCa$BB'$O$_6$ have been performed using the all-electron full-potential linearized augmented-plane-wave method. The found HM-AFM state in these materials survives the full {\it ab initio} lattice constant and atomic position optimizations which were carried out using frozen-core full potential projector augmented wave method. It is found that the HM-AFM properties predicted previously in some of the double perovskites would disappear after the full structural optimizations. The AFM is attributed to both the superexchange mechanism and the generalized double exchange mechanism via the $B$ ($t_{2g}$) - O (2$p_{\pi}$) - $B'$ ($t_{2g}$) coupling and the latter is also believed to be the origin of the HM. Finally, in our search for the HM-AFMs, we find La$A$CrTcO$_6$ and La$A$CrReO$_6$ to be AFM insulators of an unconventional type in the sense that the two antiferromagnetic coupled ions consist of two different elements and that the two spin-resolved densities of states are no longer the same.
Study on the oxygen isotope effect in A-site ordered manganite $R$BaMn$_{2}$O$_{6}$ ($R$ = La, Pr, Nd, Sm)
G. Y. Wang,K. H. Wong,Y. Wang
Physics , 2009,
Abstract: A-site ordered manganites $R$BaMn$_{2}$O$_{6}$ ($R$ = La, Pr, Nd, Sm) were synthesized and the oxygen isotope effect in them was studied. It was found that the substitution of $^{16}$O by $^{18}$O has caused increases in both the Neel temperature ($T$$_{N}$) and the charge ordering temperature ($T$$_{CO}$) and an decrease in the Curie temperature ($T$$_{C}$). The isotope exponent is small on $T$$_{C}$ and $T$$_{CO}$ compared with that in A-site disordered manganites such as La$_{1-x}$Ca$_{x}$MnO$_{3}$, which may be caused by weaker electron-phonon coupling in A-site ordered ones. But the isotope exponent of $T$$_{N}$ is large for $R$ = La. We didn't observe the large oxygen-isotope shift that occurs in NdBaMn$_{2}$O$_{6}$, where a multicritical point is believed to appear near $R$ = Nd, and strong fluctuation due to the competition between ferromagnetic metal and charge ordering phase should be present.
Quantification of atmospheric visibility with dual digital cameras during daytime and nighttime
K. Du,K. Wang,P. Shi,Y. Wang
Atmospheric Measurement Techniques Discussions , 2013, DOI: 10.5194/amtd-6-43-2013
Abstract: A digital optical method "DOM-Vis" was developed to measure atmospheric visibility. In this method, two digital pictures were taken of the same target at two different distances along the same straight line. The pictures were analyzed to determine the optical contrasts between the target and its sky background, and subsequently, visibility is calculated. A light transfer scheme for DOM-Vis was delineated, based upon which, algorithms were developed for both daytime and nighttime scenarios. A series of field tests were carried out under different weather and meteorological conditions to study the impacts of such operational parameters as exposure, optical zoom, distance between the two camera locations, and distance of the target. This method was validated by comparing the DOM-Vis results with those measured using a co-located Vaisala visibility meter. The visibility under which this study was carried out ranged from to 1 km to 20 km. This digital photography based method possesses a number of advantages compared with traditional methods. Pre-calibration of the detector with a visibility meter is not required. In addition, the application of DOM-Vis is independent of several factors like the exact distance of the target and several camera setting parameters. These features make DOM-Vis more adaptive under a variety of field conditions.
Biomarkers of drug-induced liver injury
Zhou Y, Qin S, Wang K
Current Biomarker Findings , 2013, DOI: http://dx.doi.org/10.2147/CBF.S27900
Abstract: iomarkers of drug-induced liver injury Review (1067) Total Article Views Authors: Zhou Y, Qin S, Wang K Published Date January 2013 Volume 2013:3 Pages 1 - 9 DOI: http://dx.doi.org/10.2147/CBF.S27900 Received: 26 September 2012 Accepted: 29 November 2012 Published: 14 January 2013 Yong Zhou, Shizhen Qin, Kai Wang Institute for Systems Biology, Seattle, WA, USA Abstract: The liver plays a central role in metabolizing xenobiotics; therefore, it is highly susceptible to toxicity from these chemicals. Certain drugs, when taken in overdose and sometimes even when used within therapeutic range, may cause injury to the organ. Drug-induced liver injury is now not only a leading cause of acute liver failure in the US, but is also a leading reason for discontinuation of drugs in development and for regulatory actions against previously approved drugs. The current clinical biomarkers to detect and monitor drug-induced liver injury are inadequate in terms of sensitivity and/or specificity, prompting the need for more informative biomarkers. The development of high throughput proteomics, genomics, and metabolomics technologies has the potential to fulfill such demand. The discipline of systems toxicology may add to our understanding of perturbed xenobiotic networks, which may lead to network-specific surrogate markers and therapeutic means to stop or reverse xenobiotic-induced liver injury.
Modelling debris flows down general channels
S. P. Pudasaini, Y. Wang,K. Hutter
Natural Hazards and Earth System Sciences (NHESS) & Discussions (NHESSD) , 2005,
Abstract: This paper is an extension of the single-phase cohesionless dry granular avalanche model over curved and twisted channels proposed by Pudasaini and Hutter (2003). It is a generalisation of the Savage and Hutter (1989, 1991) equations based on simple channel topography to a two-phase fluid-solid mixture of debris material. Important terms emerging from the correct treatment of the kinematic and dynamic boundary condition, and the variable basal topography are systematically taken into account. For vanishing fluid contribution and torsion-free channel topography our new model equations exactly degenerate to the previous Savage-Hutter model equations while such a degeneration was not possible by the Iverson and Denlinger (2001) model, which, in fact, also aimed to extend the Savage and Hutter model. The model equations of this paper have been rigorously derived; they include the effects of the curvature and torsion of the topography, generally for arbitrarily curved and twisted channels of variable channel width. The equations are put into a standard conservative form of partial differential equations. From these one can easily infer the importance and influence of the pore-fluid-pressure distribution in debris flow dynamics. The solid-phase is modelled by applying a Coulomb dry friction law whereas the fluid phase is assumed to be an incompressible Newtonian fluid. Input parameters of the equations are the internal and bed friction angles of the solid particles, the viscosity and volume fraction of the fluid, the total mixture density and the pore pressure distribution of the fluid at the bed. Given the bed topography and initial geometry and the initial velocity profile of the debris mixture, the model equations are able to describe the dynamics of the depth profile and bed parallel depth-averaged velocity distribution from the initial position to the final deposit. A shock capturing, total variation diminishing numerical scheme is implemented to solve the highly non-linear equations. Simulation results present the combined effects of curvature, torsion and pore pressure on the dynamics of the flow over a general basal topography. These simulation results reveal new physical insight of debris flows over such non-trivial topography. Model equations are applied to laboratory avalanche and debris-flow-flume tests. Very good agreement between the theory and experiments is established.
Barotropic response in a lake to wind-forcing
Y. Wang,K. Hutter,E. B?uerle
Annales Geophysicae (ANGEO) , 2003,
Abstract: We report results gained with a three-dimensional, semi-implicit, semi-spectral model of the shallow water equations on the rotating Earth that allowed one to compute the wind-induced motion in lakes. The barotropic response to unidirectional, uniform winds, Heaviside in time, is determined in a rectangular basin with constant depth, and in Lake Constance, for different values and vertical distributions of the vertical eddy viscosities. It is computationally demonstrated that both the transitory oscillating, as well as the steady state current distribution, depends strongly upon the absolute value and vertical shape of the vertical eddy viscosity. In particular, the excitation and attenuation in time of the inertial waves, the structure of the Ekman spiral, the thickness of the Ekman layer, and the exact distribution and magnitude of the upwelling and downwelling zones are all significantly affected by the eddy viscosities. Observations indicate that the eddy viscosities must be sufficiently small so that the oscillatory behaviour can be adequately modelled. Comparison of the measured current-time series at depth in one position of Lake Constance with those computed on the basis of the measured wind demonstrates fair agreement, including the rotation-induced inertial oscillation. Key words. Oceanography: general (limnology) – Oceanography: physical (Coriolis effects; general circulation)
A modelling study of tropospheric distributions of the trace gases CFCl3 and CH3CCl3 in the 1980s
K.-Y. Wang,D. E. Shallcross
Annales Geophysicae (ANGEO) , 2003,
Abstract: Interhemispheric transport is a key process affecting the accuracy of source quantification for species such as methane by inverse modelling, and is a source of difference among global three-dimensional chemistry transport models (CTMs). Here we use long-term observations of the atmospheric concentration of long-lived species such as CH3CCl3 and CFCl3 for testing three-dimensional chemistry transport models (CTMs); notably their ability to model the interhemispheric transport, distribution, trend, and variability of trace gases in the troposphere. The very striking contrast between the inhomogeneous source distribution and the nearly homogeneous trend, observed in the global ALE/GAGE experiments for both CH3CCl3 and CFCl3 illustrates an efficient interhemispheric transport of atmospherically long-lived chemical species. Analysis of the modelling data at two tropical stations, Barbados (13° N, 59° W) and Samoa (14° S, 124° W), show the close relationship between inter-hemispheric transport and cross-equator Hadley circulations. We found that cross-equator Hadley circulations play a key role in producing the globally homogeneous observed trends. Chemically, the most rapid interaction between CH3CCl3 and OH occurs in the northern summer troposphere; while the most rapid photolysis of CH3CCl3 and CFCl3, and the chemical reactions between CFCl3 and O(1D), take place in the southern summer stratosphere. Therefore, the cross-equator Hadley circulation plays a key role which regulates the southward flux of chemical species. The regulation by the Hadley circulations hence determines the amount of air to be processed by OH, O(1D), and ultraviolet photolysis, in both hemispheres. In summary, the dynamic regulation of the Hadley circulations, and the chemical processing (which crucially depends on the concentration of OH, O(1D), and on the intensity of solar insolation) of the air contribute to the seasonal variability and homogeneous growth rate of observed CH3CCl3 and CFCl3. Key words: Atmospheric composition and structure (middle atmosphere - composition and chemistry; pollution - urban and regional) - Meteorology and atmospheric dynamics (convective processes)
Wind-induced baroclinic response of Lake Constance
Y. Wang,K. Hutter,E. B?uerle
Annales Geophysicae (ANGEO) , 2003,
Abstract: We present results of various circulation scenarios for the wind-induced three-dimensional currents in Lake Constance, obtained with the aid of a semi-spectral semi-implicit finite difference code developed in Haidvogel et al. and Wang and Hutter. Internal Kelvin and Poincaré-type oscillations are demonstrated in the numerical results, whose periods depend upon the stratification and the geometry of the basin and agree well with measured data. By solving the eigenvalue problem of the linearized shallow water equations in the two-layered stratified Lake Constance, the interpretation of the oscillations as Kelvin and Poincaré-type waves is corroborated. Key words: Oceanography: general (limnology; numerical modeling) – Oceanography: physical (internal and inertial waves)
Biomarkers of drug-induced liver injury
Zhou Y,Qin S,Wang K
Current Biomarker Findings , 2013,
Abstract: Yong Zhou, Shizhen Qin, Kai WangInstitute for Systems Biology, Seattle, WA, USAAbstract: The liver plays a central role in metabolizing xenobiotics; therefore, it is highly susceptible to toxicity from these chemicals. Certain drugs, when taken in overdose and sometimes even when used within therapeutic range, may cause injury to the organ. Drug-induced liver injury is now not only a leading cause of acute liver failure in the US, but is also a leading reason for discontinuation of drugs in development and for regulatory actions against previously approved drugs. The current clinical biomarkers to detect and monitor drug-induced liver injury are inadequate in terms of sensitivity and/or specificity, prompting the need for more informative biomarkers. The development of high throughput proteomics, genomics, and metabolomics technologies has the potential to fulfill such demand. The discipline of systems toxicology may add to our understanding of perturbed xenobiotic networks, which may lead to network-specific surrogate markers and therapeutic means to stop or reverse xenobiotic-induced liver injury.Keywords: hepatotoxicity, idiosyncratic, metabolomics, genomics, proteomics, microRNA, systems toxicology
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