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Ming Liu

Publications and source records attributed to Ming Liu.

At least 505 records · Page 28Linked to original sources
arXiv2014

R-matrix realization of two-parameter quantum group U_{r,s}(gl_n)

We provide a Faddeev-Reshetikhin-Takhtajan's RTT approach to the quantum group Fun(GL_{r,s}(n)) and the quantum enveloping algebra U_{r,s}(gl_n) corresponding to the two-parameter R-matrix. We prove that the quantum determinant det_{r,s}T is a quasi-central element in Fun(GL_{r,s}(n)) generalizing earlier results of Dipper-Donkin and Du-Parshall-Wang. The explicit formulation provides an interpretation of the deforming parameters, and the quantized algebra U_{r,s}(R) is identified to U_{r,s}(gl_n) as the dual algebra. We then construct n-1 quasi-central elements in U_{r,s}(R) which are analogues of higher Casimir elements in U_q(gl_n).

math.QA↗
arXiv2014

Achieving Low-Complexity Maximum-Likelihood Detection for the 3D MIMO Code

The 3D MIMO code is a robust and efficient space-time block code (STBC) for the distributed MIMO broadcasting but suffers from high maximum-likelihood (ML) decoding complexity. In this paper, we first analyze some properties of the 3D MIMO code to show that the 3D MIMO code is fast-decodable. It is proved that the ML decoding performance can be achieved with a complexity of O(M^{4.5}) instead of O(M^8) in quasi static channel with M-ary square QAM modulations. Consequently, we propose a simplified ML decoder exploiting the unique properties of 3D MIMO code. Simulation results show that the proposed simplified ML decoder can achieve much lower processing time latency compared to the classical sphere decoder with Schnorr-Euchner enumeration.

cs.IT↗
arXiv2014

Reduced-complexity maximum-likelihood decoding for 3D MIMO code

The 3D MIMO code is a robust and efficient space-time coding scheme for the distributed MIMO broadcasting. However, it suffers from the high computational complexity if the optimal maximum-likelihood (ML) decoding is used. In this paper we first investigate the unique properties of the 3D MIMO code and consequently propose a simplified decoding algorithm without sacrificing the ML optimality. Analysis shows that the decoding complexity is reduced from O(M^8) to O(M^{4.5}) in quasi-static channels when M-ary square QAM constellation is used. Moreover, we propose an efficient implementation of the simplified ML decoder which achieves a much lower decoding time delay compared to the classical sphere decoder with Schnorr-Euchner enumeration.

cs.IT↗
arXiv2014

A Fast Decodable Full-Rate STBC with High Coding Gain for 4x2 MIMO Systems

In this work, a new fast-decodable space-time block code (STBC) is proposed. The code is full-rate and full-diversity for 4x2 multiple-input multiple-output (MIMO) transmission. Due to the unique structure of the codeword, the proposed code requires a much lower computational complexity to provide maximum-likelihood (ML) decoding performance. It is shown that the ML decoding complexity is only O(M^{4.5}) when M-ary square QAM constellation is used. Finally, the proposed code has highest minimum determinant among the fast-decodable STBCs known in the literature. Simulation results prove that the proposed code provides the best bit error rate (BER) performance among the state-of-the-art STBCs.

cs.IT↗
arXiv2013

Comment on "Validity of Einstein Relation in Disordered Organic Semiconductors"

Wetzelaer, Koster, and Blom [PRL 107, 066605] recently observed that the classic Einstein relation $\frac{D}μ=\frac{kT}{q}$ is still valid in disordered semiconductors in thermal(quasi)equilibrium by studying the diffusion-driven currents of single-carrier diodes. This is in contrast to the previous theoretical prediction [2] and experiment observation from Leo et.al. [3] where the Einstein relation increases with 1/T. We will discuss the reason for this discrepancy here and suggest that one-carrier diodes experiment might nor be suitable for verifying Einstein relation in organic semiconductors.

cond-mat.dis-nn↗
arXiv2013

Physical Origin of Nonlinear transport in organic semiconductor at high carrier densities

The charge transport in some organic semiconductors demonstrates nonlinear properties and further universal power-law scaling with both bias and temperature. The physical origin of this behavior is investigated here using variable range hopping theory. The results shows, this universal power-law scaling can be well explained by variable range hopping theory . Relation to the recent experimental data is also discussed.

cond-mat.mes-hall↗
arXiv2013

Non-volatile ferroelastic switching of the Verwey transition and resistivity of epitaxial Fe3O4/PMN-PT (011)

A central goal of electronics based on correlated materials or 'Mottronics' is the ability to switch between distinct collective states with a control voltage. Small changes in structure and charge density near a transition can tip the balance between competing phases, leading to dramatic changes in electronic and magnetic properties. In this work, we demonstrate that an electric field induced two-step ferroelastic switching pathway in (011) oriented 0.71Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 (PMN-PT) substrates can be used to tune the Verwey metal-insulator transition in epitaxial Fe3O4 films in a stable and reversible manner. We also observe robust non-volatile resistance switching in Fe3O4 up to room temperature, driven by ferroelastic strain. These results provides a framework for realizing non-volatile and reversible tuning of order parameters coupled to lattice-strain in epitaxial oxide heterostructures over a broad range of temperatures, with potential device applications.

cond-mat.mtrl-sci↗
arXiv2013

Charge transfer and interfacial magnetism in (LaNiO3)n/(LaMnO3)2 superlattices

(LaNiO3)n/(LaMnO3)2 superlattices were grown using ozone-assisted molecular beam epitaxy, where LaNiO3 is a paramagnetic metal and LaMnO3 is an antiferromagnetic insulator. The superlattices exhibit excellent crystallinity and interfacial roughness of less than 1 unit cell. X-ray spectroscopy and dichroism measurements indicate that electrons are transferred from the LaMnO3 to the LaNiO3, inducing magnetism in LaNiO3. Magnetotransport measurements reveal a transition from metallic to insulating behavior as the LaNiO3 layer thickness is reduced from 5 unit cells to 2 unit cells and suggest a modulated magnetic structure within LaNiO3.

cond-mat.mtrl-sci↗
arXiv2013

Wedge modules for two-parameter quantum groups

The Yang-Baxterization R(z) of the trigonometric R-matrix is computed for the two-parameter quantum affine algebra of type A. Using the fusion procedure we construct all fundamental representations of the quantum algebra as wedge products of the natural representation.

math.QA↗
arXiv2013

Charge carrier relaxation model in hopping system

The relaxation phenomena of charge carriers in hopping system have been demonstrated and investigated theoretically. An analytical model describing the charge carrier relaxation is proposed based on the hopping transport theory. The relation between the material disorder, electric field and temperature and the relaxation phenomena has been discussed in detail, respectively. The calculated results reveal that the increase of electric field and temperature can promote the relaxation effect in disordered systems, while the increase of material disorder will weaken the relaxation. The proposed model can explain well the stretched-exponential law by adopting the appropriate parameters. The calculation shows a good agreement with the experimental data for organic semiconductors.

cond-mat.mtrl-sci↗
arXiv2013

Generalized Bell states and principal realization of the Yangian Y(sl_N)

We prove that the action of the Yangian algebra Y(sl_N) is better described by the principal generators on the tensor product of the fundamental representation and its dual. The generalized Bell states or maximally entangled states are permuted by the principal generators in a dramatically simple manner on the tensor product. Under the Yangian symmetry the new quantum number J^2 is also explicitly computed, which gives an explanation for these maximally entangled states.

math.QA↗
arXiv2012

Distributed MIMO coding scheme with low decoding complexity for future mobile TV broadcasting

A novel distributed space-time block code (STBC) for the next generation mobile TV broadcasting is proposed. The new code provides efficient performance within a wide range of power imbalance showing strong adaptivity to the single frequency network (SFN) broadcasting deployments. The new code outperforms existing STBCs with equivalent decoding complexity and approaches those with much higher complexities.

cs.NI↗
arXiv2012

Enhanced Mobile Digital Video Broadcasting with Distributed Space-Time Coding

This paper investigates the distributed space-time (ST) coding proposals for the future Digital Video Broadcasting--Next Generation Handheld (DVB-NGH) standard. We first theoretically show that the distributed MIMO scheme is the best broadcasting scenario in terms of channel capacity. Consequently we evaluate the performance of several ST coding proposals for DVB-NGH with practical system specifications and channel conditions. Simulation results demonstrate that the 3D code is the best ST coding solution for broadcasting in the distributed MIMO scenario.

cs.IT↗
arXiv2012

Improved Channel Estimation Methods based on PN sequence for TDS-OFDM

An accurate channel estimation is crucial for the novel time domain synchronous orthogonal frequency-division multiplexing (TDS-OFDM) scheme in which pseudo noise (PN) sequences serve as both guard intervals (GI) for OFDM data symbols and training sequences for synchronization/channel estimation. This paper studies the channel estimation method based on the cross-correlation of PN sequences. A theoretical analysis of this estimator is conducted and several improved estimators are then proposed to reduce the estimation error floor encountered by the PN-correlation-based estimator. It is shown through mathematical derivations and simulations that the new estimators approach or even achieve the Cramer-Rao bound.

cs.IT↗
arXiv2012

Comments on "Unusual Thermoelectric Behavior Indicating a Hopping to Bandlike Transport Transition in Pentacene"

W. Chr. Germs, K. Guo, R. A. J. Janssen, and M. Kemerink [1] recently measured the temperature and concentration dependent seebeck coefficient in organic thin film transistor and found the seebeck coefficient increases with carrier concentration (corresponding to the gate voltage) in the low temperature regime. They further concluded that this unusual behavior is due to a transition from hopping transport in static localized states to bandlike transport, occurring at low temperatures. This is obviously in contrast to the previous theoretical prediction because it is widely accepted that hopping transport is more pronounced at low temperature. We will discuss the reason for this unusual behavior here and suggest that the density of states function plays an important role in concentration dependent seebeck coefficient.

cond-mat.dis-nn↗
arXiv2012

Validity of Transport Energy in Disordered Organic Semiconductors

A systematic study of the transport energy in disordered organic semiconductors based on variable range hopping theory has been presented here. The temperature, electric field, material disorder and carrier concentration dependent transport energy is extensively discussed. We demonstrate here, transport energy is not a general concept and invalid even in low electric field and concentration regime.

cond-mat.dis-nn↗