Blow-up in reaction-diffusion systems under Robin boundary conditions

In this paper we apply the differential inequality technique of Payne {\it et. al} \cite{Payne&SchaeferRobin08} to show that a reaction-diffusion system admits blow-up solutions, and to determine an upper bound for the blow-up time. For a particular nonlinearity, a lower bound on the blow-up time, when blow-up does occur, is also given.Comment: 11 page

An N-barrier maximum principle for elliptic systems arising from the study of traveling waves in reaction-diffusion systems

By employing the N-barrier method developed in the paper, we establish a new N-barrier maximum principle for diffusive Lotka-Volterra systems of two competing species. As an application of this maximum principle, we show under certain conditions, the existence and nonexistence of traveling waves solutions for systems of three competing species. In addition, new $(1,0,0)$-$(u^{\ast},v^{\ast},0)$ waves are given in terms of the tanh function provided that the parameters satisfy certain conditions.Comment: 24 page

Locally Weighted Learning for Naive Bayes Classifier

As a consequence of the strong and usually violated conditional independence assumption (CIA) of naive Bayes (NB) classifier, the performance of NB becomes less and less favorable compared to sophisticated classifiers when the sample size increases. We learn from this phenomenon that when the size of the training data is large, we should either relax the assumption or apply NB to a "reduced" data set, say for example use NB as a local model. The latter approach trades the ignored information for the robustness to the model assumption. In this paper, we consider using NB as a model for locally weighted data. A special weighting function is designed so that if CIA holds for the unweighted data, it also holds for the weighted data. The new method is intuitive and capable of handling class imbalance. It is theoretically more sound than the locally weighted learners of naive Bayes that base classification only on the $k$ nearest neighbors. Empirical study shows that the new method with appropriate choice of parameter outperforms seven existing classifiers of similar nature

On generalization of D'Aurizio-S\'andor trigonometric inequalities with a parameter

In this work, we generalize the D'Aurizio-S\'andor inequalities (\cite{D'Aurizio,Sandor}) using an elementary approach. In particular, our approach provides an alternative proof of the D'Aurizio-S\'andor inequalities. Moreover, as an immediate consequence of the generalized D'Aurizio-S\'andor inequalities, we establish the D'Aurizio-S\'andor-type inequalities for hyperbolic functions

On the Full Column-Rank Condition of the Channel Estimation Matrix in Doubly-Selective MIMO-OFDM Systems

Recently, this journal has published a paper which dealt with basis expansion model (BEM) based least-squares (LS) channel estimation in doubly-selective orthogonal frequency-division multiplexing (DS-OFDM) systems. The least-squares channel estimator computes the pseudo-inverse of a channel estimation matrix. For the existence of the pseudo-inverse, it is necessary that the channel estimation matrix be of full column rank. In this paper, we investigate the conditions that need to be satisfied that ensures the full column-rank condition of the channel estimation matrix. In particular, we derive conditions that the BEM and pilot pattern designs should satisfy to ensure that the channel estimation matrix is of full column rank. We explore the polynomial BEM (P-BEM), complex exponential BEM (CE-BEM), Slepian BEM (S-BEM) and generalized complex exponential BEM (GCE-BEM). We present one possible way to design the pilot patterns which satisfy the full column-rank conditions. Furthermore, the proposed method is extended to the case of multiple-input multiple-output (MIMO) DS-OFDM systems as well. Examples of pilot pattern designs are presented, that ensure the channel estimation matrix is of full column rank for a large DS-MIMO-OFDM system with as many as six transmitters, six receivers and 1024 subcarriers.Comment: 19 Pages, 4 figures, currently under review in IEEE Transactions Signal Processin

Physical masses and the vacuum expectation value of the Higgs field

By using the Ward-Takahashi identities in the Landau gauge, we derive exact relations between particle masses and the vacuum expectation value of the Higgs field in the Abelian gauge field theory with a Higgs meson.Comment: Latex, 7 page

The Standard Model in the Alpha gauge is not renormalizable

We study the Ward-Takahashi identities in the standard model with the gauge fixing terms given by (1.1) and (1.2). We find that the isolated singularities of the propagators for the unphysical particles are poles of even order, not the simple poles people have assumed them to be. Furthermore, the position of these poles are ultraviolet divergent. Thus the standard model in the alpha gauge in general, and the Feynman gauge in particular, is not renormalizable. We study also the case with the gauge fixing terms (1.3), and find that the propagators remain non-renormalizable. The only gauge without these difficulties is the Landau gauge. One therefore has to make a distinction between the renormalizability of the Green functions and that of the physical scattering amplitudes.Comment: 26 pages, LaTe

Level raising mod 2 and arbitrary 2-Selmer ranks

We prove a level raising mod $\ell=2$ theorem for elliptic curves over $\mathbb{Q}$. It generalizes theorems of Ribet and Diamond-Taylor and also explains different sign phenomena compared to odd $\ell$. We use it to study the 2-Selmer groups of modular abelian varieties with common mod 2 Galois representation. As an application, we show that the 2-Selmer rank can be arbitrary in level raising families.Comment: To appear in Compos. Mat

Random Cell Association and Void Probability in Poisson-Distributed Cellular Networks

This paper studied the fundamental modeling defect existing in Poisson-distributed cellular networks in which all base stations form a homogeneous Poisson point process (PPP) of intensity $\lambda_B$ and all users form another independent PPP of intensity $\lambda_U$. The modeling defect, hardly discovered in prior works, is the void cell issue that stems from the independence between the distributions of users and BSs and "user-centric" cell association, and it could give rise to very inaccurate analytical results. We showed that the void probability of a cell under generalized random cell association is always bounded above zero and its theoretical lower bound is $\exp(-\frac{\lambda_U}{\lambda_B})$ that can be achieved by large association weighting. An accurate expression of the void probability of a cell was derived and simulation results validated its correctness. We also showed that the associated BSs are essentially no longer a PPP such that modeling them as a PPP to facilitate the analysis of interference-related performance metrics may detach from reality if the BS intensity is not significantly large if compared with the user intensity.Comment: 7 pages, 4 figures, conference (Figures are updated in this version

Search of DsJ∗D^{*}_{sJ} mesons in BB meson decays

We propose that the search of the $B\to D^{*}_{sJ}M$ decays, $M=D$, $\pi$ and $K$, can discriminate the different theoretical postulations for the nature of the recently observed $D^{*}_{sJ}$ mesons. The ratio of the branching ratios $B(B\to D^{*}_{sJ}M)/B(B\to D^{(*)}_{s}M)\approx 1$ (0.1) supports that the $D^{*}_{sJ}$ mesons are quark-antiquark (multi-quark) bound states. The Belle measurement of the $B\to D^{*}_{sJ}D$ branching ratios seems to indicate an unconventional picture.Comment: 5 pages, 1 figure, Revtex