Lattice QCD calculation of ππ\pi\pi scattering length

We study s-wave pion-pion ($\pi\pi$) scattering length in lattice QCD for pion masses ranging from 330 MeV to 466 MeV. In the "Asqtad" improved staggered fermion formulation, we calculate the $\pi\pi$ four-point functions for isospin I=0 and 2 channels, and use chiral perturbation theory at next-to-leading order to extrapolate our simulation results. Extrapolating to the physical pion mass gives the scattering lengths as $m_\pi a_0^{I=2} = -0.0416(2)$ and $m_\pi a_0^{I=0} = 0.186(2)$ for isospin I=2 and 0 channels, respectively. Our lattice simulation for $\pi\pi$ scattering length in the I=0 channel is an exploratory study, where we include the disconnected contribution, and our preliminary result is near to its experimental value. These simulations are performed with MILC 2+1 flavor gauge configurations at lattice spacing $a \approx 0.15$ fm.Comment: Remove some typo

On QGP Formation in pp Collisions at 7 TeV

The possibility of QGP formation in central pp collisions at ultra-high collision energy is discussed. Centrality-dependent \pt-spectra and (pseudo)rapidity spectra of thermal photons (charged hadrons) from pp collisions at 7 TeV are presented (addressed). Minimal-bias \pt-spectrum of direct photons and charged hadrons is compared under the framework with and without hydrodynamical evolution process.Comment: 4pages, 5figs, submitted to the Proceedings of the 22nd International Conference on Ultra-relativistic Nucleus-Nucleus Collision (Quark Matter 2011), 23 - 28 May 2011, Annecy, Franc

Cardiomyopathy Causing Mutations Stabilize an Intermediate State of Thin Filaments

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this recordWhen solving constrained multi-objective optimization problems, an important issue is how to balance convergence, diversity and feasibility simultaneously. To address this issue, this paper proposes a parameter-free constraint handling technique, a two-archive evolutionary algorithm, for constrained multi-objective optimization. It maintains two collaborative archives simultaneously: one, denoted as the convergence-oriented archive (CA), is the driving force to push the population toward the Pareto front; the other one, denoted as the diversity-oriented archive (DA), mainly tends to maintain the population diversity. In particular, to complement the behavior of the CA and provide as much diversified information as possible, the DA aims at exploring areas under-exploited by the CA including the infeasible regions. To leverage the complementary effects of both archives, we develop a restricted mating selection mechanism that adaptively chooses appropriate mating parents from them according to their evolution status. Comprehensive experiments on a series of benchmark problems and a real-world case study fully demonstrate the competitiveness of our proposed algorithm, in comparison to five state-of-the-art constrained evolutionary multi-objective optimizers.Royal Society (Government)Ministry of Science and Technology of ChinaScience and Technology Innovation Committee Foundation of ShenzhenShenzhen Peacock PlanEngineering and Physical Sciences Research Council (EPSRC

A Novel Method for Landslide Displacement Prediction by Integrating Advanced Computational Intelligence Algorithms

Landslide displacement prediction is considered as an essential component for developing early warning systems. The modelling of conventional forecast methods requires enormous monitoring data that limit its application. To conduct accurate displacement prediction with limited data, a novel method is proposed and applied by integrating three computational intelligence algorithms namely: the wavelet transform (WT), the artificial bees colony (ABC), and the kernel-based extreme learning machine (KELM). At first, the total displacement was decomposed into several sub-sequences with different frequencies using the WT. Next each sub-sequence was predicted separately by the KELM whose parameters were optimized by the ABC. Finally the predicted total displacement was obtained by adding all the predicted sub-sequences. The Shuping landslide in the Three Gorges Reservoir area in China was taken as a case study. The performance of the new method was compared with the WT-ELM, ABC-KELM, ELM, and the support vector machine (SVM) methods. Results show that the prediction accuracy can be improved by decomposing the total displacement into sub-sequences with various frequencies and by predicting them separately. The ABC-KELM algorithm shows the highest prediction capacity followed by the ELM and SVM. Overall, the proposed method achieved excellent performance both in terms of accuracy and stability

Shear Strength of Fiber Reinforced Reactive Powder Concrete I-Shaped Beam without Stirrup

Due to the high compressive strength of steel fiber reinforced (SFR) and Reactive Powder concrete (RPC), higher degree of prestressing is available for the beams using fiber reinforced reactive powder concrete. Hence, a slenderer structural component can be designed, which could save self-weight, work spacing, and potential reducing the costs. However, comparing to conventional reinforced concrete (RC) beams, studies on post-tensioning SFR-RPC beams subjected to shear failure are fewer. In this study, a series of shear tests for four large-scale beams (one SFR-RPC beam and three post-tensioning SFR-RPC beams) are made to quantify the effects of levels of prestressing on shear load capacity of SFR-RPC beams. Finally, the test results together with data published from existing literatures are compared to the design strength calculated in accordance to different standards. It is found that the current code provisions will underestimate the shear load capacity significantly. In addition, an analytical model is proposed to predict the shear load capacity of the test specimens. A good correlation is observed with a mean analytical model to experimental strength ratio of 1.02 and coefficient of variation of 0.12

Effects of High Strength Concrete on Progressive Collapse Resistance of Reinforced Concrete Frame

Increasing terrorist activities in the past decade brought requirements in design buildings, especially government or commercial buildings, under extreme loading conditions. One of the devastating consequences due to extreme loading is the possibility of progressive collapse. Although extensive studies had been carried out in the past decade on load resistance mechanism of reinforced concrete (RC) frames in preventing progressive collapse, the effects of high-strength-concrete (HSC) on progressive collapse resistance capacity is still unclear. Therefore, in this paper six tests of reinforced concrete frames with different span-to-depth ratio and concrete strength were conducted in the present study. Among them, three are HSC frames and the remaining are normal strength concrete frames. It was found that the use of HSC could further enhance the compressive arch action (CAA) capacity, especially for those with low span-to-depth ratio. On the other hand, HSC can reduce the tensile catenary action (TCA) capacity at large deformation stage, primarily because of higher bond stress between concrete and rebar,leading to earlier fracture of the rebar.The analytical results from the model were compared with the test results. It is found that the existing CAA model could accurately predict the CAA capacity of HSC frames as well as NSC frames.However, existing model is hard to predict the CAA capacity of the frames with relatively small span-to-depth ratio (less than 7) accurately

Progressive Collapse Resisting Mechanisms of Planar Prestressed Concrete Frame

The paper presents the behavior of six tests of Planar Prestressed Concrete Frame under the loss of a middle column. The six tests consist of two non-prestressed reinforced concrete (RC) specimens and four prestressed concrete (PC) specimens with bonded post-tensioning tendons (BPT). The structural response of the specimens with different flexural reinforcement ratio, span/depth ratio, and effective prestress level has been reported. In addition, the impact of parabolic BPT on the behavior of RC frames to resist progressive collapse is also evaluated. Experimental results indicated that the BPT can not only increase the initial stiffness and yielding load of the RC counterparts, but also increase the ultimate load capacity in the catenary action stage. Moreover, it will impact the load resisting mechanisms and the failure modes. Contrary to the commonly accepted sequential mobilization of compressive arch action and catenary action to resist progressive collapse of RC frames, no effective The paper presents the behavior of six tests of Planar Prestressed Concrete Frame under the compressive arch action is developed in PC frames to mitigate progressive collapse risk. Based on experimental observations, it is found that higher effective prestress in BPT results in enhanced initial stiffness and yielding load but less deformation capacity and ultimate load capacity. It is also found that higher non-prestressed flexural tensile reinforcement ratio could improve the behavior of PC specimens to resist progressive collapse

SU(3) Predictions of B→PPB\to PP Decays in the Standard Model

With SU(3) symmetry one only needs 13 hadronic parameters to describe $B\to PP$ decays in the Standard Model. When annihilation contributions are neglected, only 7 hadronic parameters are needed. These parameters can be determined from existing experimental data and some unmeasured branching ratios and CP asymmetries of the type $B\to PP$ can be predicted. In this talk we present SU(3) predictions of branching ratios and CP asymmetries for $B\to PP$ decays in the Standard Model.Comment: 4 pages, no figure. Talk present at the 5th International Conference on Hyperons, Charm and Beauty Hadrons, Vancouver, June 200

Experimental Study on Seismic Behaviour of RC Frames with Different Infilled Masonry

Six 1/2 scaled, single-storey, one-bay frame specimens were tested in this study to investigate the seismic behavior of masonry infilled reinforced concrete (RC) frames subjected to lateral loading. The variables investigated include types of masonry and types of openings. The crack patterns, failure modes, load-displacement hysteretic loops, stiffness degradation, and energy dissipation capacity are presented and discussed. It is found that the infilled wall (with or without openings) could improve the behavior of RC frames significantly. Moreover, as expected, the infilled frame with higher strength masonry performed better than those with relatively low strength masonry. Furthermore, the openings may detriment the stability of the infilled walls. The concentric widow opening has worse effects than the eccentric door opening. The proposed analytical model could determine the load resisting capacity of bare frame and infilled frame with reasonable accuracy