Pressure condition for lattice Boltzmann methods on domains with curved boundaries

AbstractWe propose a lattice Boltzmann algorithm for an average pressure boundary condition at outlets in pipe flow systems. The advantage of this boundary condition is that only the average pressure is used to recover the non-trivial flow fields. The asymptotic analysis shows that this algorithm works for general curved boundaries and renders a second order accurate velocity and a first order accurate pressure approximation of the incompressible Navier–Stokes solution. Here, we verify the accuracy by numerical simulations of a Poiseuille flow and a less symmetric flow with non-trivial pressure field in channels inclined with arbitrary angle, and flows in a pipe with three outlets

Top quark forward-backward asymmetry at the Tevatron: a comparative study in different new physics models

The top quark forward-backward asymmetry A_{FB}^t measured at the Tevatron is above the Standard Model prediction by more than 2-sigma deviation, which might be a harbinger for new physics. In this work we examine the contribution to A_{FB}^t in two different new physics models: one is the minimal supersymmetric model without R-parity (RPV-MSSM) which contributes to A_{FB}^t via sparticle-mediated t-channel process d d_bar-> t t_bar; the other is the third-generation enhanced left-right model (LR model) which contributes to A_{FB}^t via Z'-mediated t-channel or s-channel processes. We find that in the parameter space allowed by the tt_bar production rate and the tt_bar invariant mass distribution at the Tevatron, the LR model can enhance A_{FB}^t to within the 2-sigma region of the Tevatron data for the major part of the parameter space, and in optimal case A_{FB}^t can reach 12% which is slightly below the 1-sigma lower bound. For the RPV-MSSM, only in a narrow part of the parameter space can the \lambda'' couplings enhance A_{FB}^t to within the 2-sigma region while the \lambda' couplings just produce negative contributions to worsen the fit.Comment: Version in PRD (RPV-MSSM lambda" effects added

Pair production of 125 GeV Higgs boson in the SM extension with color-octet scalars at the LHC

Although the Higgs boson mass and single production rate have been determined more or less precisely, its other properties may deviate significantly from its predictions in the standard model (SM) due to the uncertainty of Higgs data. In this work we study the Higgs pair production at the LHC in the Manohar-Wise model, which extends the SM by one family of color-octet and isospin-doublet scalars. We first scanned over the parameter space of the Manohar-Wise model considering exprimental constraints and performed fits in the model to the latest Higgs data by using the ATLAS and CMS data separately. Then we calculated the Higgs pair production rate and investigated the potential of its discovery at the LHC14. We conclude that: (i) Under current constrains including Higgs data after Run I of the LHC, the cross section of Higgs pair production in the Manohar-Wise model can be enhanced up to even $10^3$ times prediction in the SM. (ii) Moreover, the sizable enhancement comes from the contributions of the CP-odd color-octet scalar $S^A_I$. For lighter scalar $S^A_I$ and larger values of $|\lambda_I|$, the cross section of Higgs pair production can be much larger. (iii) After running again of LHC at 14 TeV, most of the parameter spaces in the Manohar-Wise model can be test. For an integrated luminosity of 100 fb$^{-1}$ at the LHC14, when the normalized ratio $R=10$, the process of Higgs pair production can be detected.Comment: 13 pages, 4 figure

Pair Production of a 125 GeV Higgs Boson in MSSM and NMSSM at the LHC

In light of the recent LHC Higgs search data, we investigate the pair production of a SM-like Higgs boson around 125 GeV in the MSSM and NMSSM. We first scan the parameter space of each model by considering various experimental constraints, and then calculate the Higgs pair production rate in the allowed parameter space. We find that in most cases the dominant contribution to the Higgs pair production comes from the gluon fusion process and the production rate can be greatly enhanced, maximally 10 times larger than the SM prediction (even for a TeV-scale stop the production rate can still be enhanced by a factor of 1.3). We also calculate the chi-square value with the current Higgs data and find that in the most favored parameter region the production rate is enhanced by a factor of 1.45 in the MSSM, while in the NMSSM the production rate can be enhanced or suppressed (\sigma_{SUSY}/\sigma_{SM} varies from 0.7 to 2.4).Comment: 15 pages, 5 figure

New Framework for Code-Mapping-based Reversible Data Hiding in JPEG Images

Code mapping (CM) is an efficient technique of reversible data hiding (RDH) in JPEG images, which embeds data by constructing the mapping relationship between used codes and unused codes in JPEG bitstream. In this paper, we present a new framework to design the CM-based RDH method. Firstly, to suppress the file size expansion and improve the applicability, a new code mapping strategy is proposed. Based on the proposed strategy, the mapped codes are redefined by customizing a new Huffman table thoroughly rather than selected from the unused codes in the original Huffman table. Afterwards, the key issue of designing the CM-based RDH method, i.e., constructing the code mapping, is converted into solving a combinatorial optimization problem. As a realization, a novel CM-based RDH method is introduced by employing the genetic algorithm (GA). Experimental results show that the efficacy of the proposed method with high embedding capacity and no signal distortion while suppressing file size expansion

The Development of Mobile Short Video Communication in the Context of the Mobile Internet

In the context of the mobile Internet, continuously upgraded media and increasing numbers of terminal devices has enabled information communication to become instant and abundant. The lifestyle of the public has also changed with the evolution of the Internet. The public’s growing enthusiasm for watching short videos on smart phones are one example. This paper discusses changes in the communication environment, namely the concept and development of mobile short videos. Application of Lasswell’s “5W” model to mobile short video communication, is used to analyze this form of communication, using Meipai, a Chinese mobile short video application, as a case study. Suggestions for potential development in this area are also considered

Power Decoupling Control and Optimization for a Photovoltaic Inverter in D-Q Rotation Frame

In the past decade, solar energy, the fastest growing renewable energy, has been a growing interest in integration to the utility grid. Power electronics converters play important role in renewable energy integration, e.g., integrate the distributed photovoltaic (PV) panels to the grid. In many applications, particularly in the residential area, a single-phase rather than three-phase inverter is used to regulate the voltage from one form to the other while tracking the maximum power point of the PV system. The input voltage and current are DC and its maximum power is desired to be a constant value. However, in the single-phase PV inverter, the sinusoidal voltage and current waveform makes the output power pulsated with double frequency, which results in the power mismatch between the input and the output. Therefore, it is necessary to use energy buffer to balance the power, i.e., the power decoupling. In this work, a power decoupling method first is developed in d-q rotation frame and is optimized so that the energy buffer can be minimized. The power decoupling controller designed in the d-q frame has the superiority of simplicity so that the traditional proportional integral (PI) control can be used. Besides, a composite power decoupling method which includes both DC side passive and AC side active power decoupling is developed. Due to the use of two stage power decoupling, the energy buffer, e.g., capacitance at the DC and AC side, is minimized. Meanwhile, the important functions such as the maximum power point tracking (MPPT) and relatively high power quality are achieved

The Phenomenological Research on Higgs and dark matter in the Next-to-Minimal Supersymmetric Standard Model

The $Z_3$-invariant next-to-minimal supersymmetric standard model (NMSSM) can provide a candidate for dark matter (DM). It can also be used to explain the hypothesis that the Higgs signal observed on the Large Hadron Collider (LHC) comes from the contribution of the two lightest CP-even Higgs bosons, whose masses are near 125 GeV. At present, XENON1T, LUX, and PandaX experiments have imposed very strict restrictions on direct collision cross sections of {dark matter}. In this paper, we consider a scenario that the observed Higgs signal is the superposition of two mass-degenerate Higgs in the $Z_3$-invariant NMSSM and scan the seven-dimension parameter space composing of $\lambda, \kappa, \tan\beta, \mu, A_k, A_t, M_1$ via the Markov chain Monte Carlo (MCMC) method. We find that the DM relic density, as well as the LHC searches for sparticles, especially the DM direct detections, has provided a strong limit on the parameter space. %Please check intended meaning has been retained. The allowed parameter space is featured by a relatively small $\mu \le 300$ GeV and about $\tan\beta\in(10,20)$. In addition, the DM is Higgsino-dominated because of $|\frac{2\kappa}{\lambda}|>1$. Moreover, the co-annihilation between $\tilde{\chi}_1^0$ and $\tilde{\chi}_1^\pm$ must be taken into account to obtain the reasonable DM relic density