Trellis-Coded Non-Orthogonal Multiple Access

In this letter, we propose a trellis-coded non-orthogonal multiple access (NOMA) scheme. The signals for different users are produced by trellis coded modulation (TCM) and then superimposed on different power levels. By interpreting the encoding process via the tensor product of trellises, we introduce a joint detection method based on the Viterbi algorithm. Then, we determine the optimal power allocation between the two users by maximizing the free distance of the tensor product trellis. Finally, we manifest that the trellis-coded NOMA outperforms the uncoded NOMA at high signal-to-noise ratio (SNR)

Poisson noise induced switching in driven micromechanical resonators

We study Poisson-noise induced switching between coexisting vibrational states in driven nonlinear micromechanical resonators. In contrast to Gaussian noise induced switching, the measured logarithm of the switching rate is proportional not to the reciprocal noise intensity, but to its logarithm, for fixed pulse area. We also find that the switching rate logarithm varies as a square root of the distance to the bifurcation point, instead of the conventional scaling with exponent 3/2.Comment: accepted by PR

High-Mobility Few-Layer Graphene Field Effect Transistors Fabricated on Epitaxial Ferroelectric Gate Oxides

The carrier mobility \mu of few-layer graphene (FLG) field-effect transistors increases ten-fold when the SiO_2 substrate is replaced by single-crystal epitaxial Pb(Zr_0.2Ti_0.8)O_3 (PZT). In the electron-only regime of the FLG, \mu reaches 7x10^4 cm^2/Vs at 300K for n = 2.4x10^12/cm^2, 70% of the intrinsic limit set by longitudinal acoustic (LA) phonons; it increases to 1.4x10^5 cm^2/Vs at low temperature. The temperature-dependent resistivity \rho(T) reveals a clear signature of LA phonon scattering, yielding a deformation potential D = 7.8+/-0.5 eV.Comment: 5 pages, 4 figure

Friend or foe? The role of state and mutual Fund ownership in the split share structure reform in China

The recent split share structure reform in China involves the nontradable shareholders proposing a compensation package to the tradable shareholders in exchange for the listing rights of their shares. We find that state ownership (the major owners of nontradable shares) has a positive effect on the final compensation ratio. In contrast, mutual fund ownership (the major institutional owner of tradable shares) has a negative effect on the compensation ratio and especially in state-owned firms. The evidence is consistent with our predictions that state shareholders have incentives to complete the reform quickly and exert political pressure on mutual funds to accept the terms without a fight. Copyright © 2010 Michael G. Foster School of Business, University of Washington.published_or_final_versio

Chief executive officer incentives, monitoring, and corporate risk management: Evidence from insurance use

Corporate governance and risk management issues have received prominent publicity in recent years following several major company failures such as Bear Stearns and Lehman Brothers. While prior studies have examined this issue within the context of derivatives' trading, little is known regarding the linkage between corporate governance and alternative corporate risk management activities such as insurance. Using a detailed firm survey conducted by the World Bank (2004), we examine the impacts of various governance monitoring mechanisms and chief executive officer (CEO) characteristics on the corporate insurance decision. Overall, our results suggest that both monitoring mechanisms and managerial incentives induce the corporate purchase of property insurance. However, the purchase of property insurance for managerial self-interest is only prevalent in firms subject to lax monitoring, and the determinants of insurance purchases are more in line with the prediction of the economic theory in firms with strong monitoring. In addition, our study contributes a number of new insights into the determinants of corporate purchase of property insurance. © The Journal of Risk and Insurance, 2011.preprin

On the possibility of superconductivity in PrBa2Cu3O7

Recent reports about observations of superconductivity in PrBa2Cu3O7 raise a number of questions: (i) of various theories striving to explain the Tc suppression in PrxY{1-x}Ba2Cu3O7, are there any compatible with possible superconductivity in stoichiometric PrBa2Cu3O7? (ii) if this superconductivity is not an experimental artifact, are the superconducting carriers (holes) of the same character as in the other high-Tc cuprates, or do they represent another electronic subsystem? (iii) is the underlying mechanism the same as in other high-Tc superconductors? I present an answer to the first two questions, while leaving the last one open.Comment: 4 pages 4 eps fig

An effective method of calculating the non-Markovianity N\mathcal{N} for single channel open systems

We propose an effective method which can simplify the optimization of the increase of the trace distance over all pairs of initial states in calculating the non-Markovianity $\mathcal{N}$ for single channel open systems. For the amplitude damping channel, we can unify the results of Breuer $et$ $al$. [Phys. Rev. Lett. \bf 103\rm, 210401 (2009)] in the large-detuning case and the results of Xu $et$ $al$. [Phys. Rev. A \bf 81\rm, 044105 (2010)] in the resonant case; furthermore, for the general off-resonant cases we can obtain a very tight lower bound of $\mathcal{N}$. As another application of our method, we also discuss $\mathcal{N}$ for the non-Markovian depolarizing channel.Comment: 7 pages, 3 figures,to be published in Phys. Rev.

The private capacity of quantum channels is not additive

Recently there has been considerable activity on the subject of additivity of various quantum channel capacities. Here, we construct a family of channels with sharply bounded classical, hence private capacity. On the other hand, their quantum capacity when combined with a zero private (and zero quantum) capacity erasure channel, becomes larger than the previous classical capacity. As a consequence, we can conclude for the first time that the classical private capacity is non-additive. In fact, in our construction even the quantum capacity of the tensor product of two channels can be greater than the sum of their individual classical private capacities. We show that this violation occurs quite generically: every channel can be embedded into our construction, and a violation occurs whenever the given channel has larger entanglement assisted quantum capacity than (unassisted) classical capacity.Comment: 4+4 pages, 2 eps figures. V2 has title and abstract changed; its new structure reflects the final version of a main paper plus appendices containing mathematical detail

The packing of granular polymer chains

Rigid particles pack into structures, such as sand dunes on the beach, whose overall stability is determined by the average number of contacts between particles. However, when packing spatially extended objects with flexible shapes, additional concepts must be invoked to understand the stability of the resulting structure. Here we study the disordered packing of chains constructed out of flexibly-connected hard spheres. Using X-ray tomography, we find long chains pack into a low-density structure whose mechanical rigidity is mainly provided by the backbone. On compaction, randomly-oriented, semi-rigid loops form along the chain, and the packing of chains can be understood as the jamming of these elements. Finally we uncover close similarities between the packing of chains and the glass transition in polymers.Comment: 11 pages, 4 figure

Manifold Elastic Net: A Unified Framework for Sparse Dimension Reduction

It is difficult to find the optimal sparse solution of a manifold learning based dimensionality reduction algorithm. The lasso or the elastic net penalized manifold learning based dimensionality reduction is not directly a lasso penalized least square problem and thus the least angle regression (LARS) (Efron et al. \cite{LARS}), one of the most popular algorithms in sparse learning, cannot be applied. Therefore, most current approaches take indirect ways or have strict settings, which can be inconvenient for applications. In this paper, we proposed the manifold elastic net or MEN for short. MEN incorporates the merits of both the manifold learning based dimensionality reduction and the sparse learning based dimensionality reduction. By using a series of equivalent transformations, we show MEN is equivalent to the lasso penalized least square problem and thus LARS is adopted to obtain the optimal sparse solution of MEN. In particular, MEN has the following advantages for subsequent classification: 1) the local geometry of samples is well preserved for low dimensional data representation, 2) both the margin maximization and the classification error minimization are considered for sparse projection calculation, 3) the projection matrix of MEN improves the parsimony in computation, 4) the elastic net penalty reduces the over-fitting problem, and 5) the projection matrix of MEN can be interpreted psychologically and physiologically. Experimental evidence on face recognition over various popular datasets suggests that MEN is superior to top level dimensionality reduction algorithms.Comment: 33 pages, 12 figure