4,328 research outputs found
Improving Performance in Combinatorial Optimisation Using Averaging and Clustering
No full textIn a recent paper an algorithm for solving MAX-SAT was proposed which worked by clustering good solutions and restarting the search from the closest feasible solutions. This was shown to be an extremely effective search strategy, substantially out-performing traditional optimisation techniques. In this paper we extend those ideas to a second classic NP-Hard problem, namely Vertex Cover. Again the algorithm appears to provide an advantage over more established search algorithms, although it shows different characteristics to MAX-SAT. We argue this is due to the different large-scale landscape structure of the two problems
Learning the large-scale structure of the max-sat landscape using populations
No full textA new algorithm for solving MAX-SAT problems is introduced which clusters good solutions, and restarts the search from the closest feasible solution to the centroid of each cluster. This is shown to be highly efficient for finding good solutions of large MAX-SAT problems. We argue that this success is due to the population learning the large-scale structure of the fitness landscape. Systematic studies of the landscape are presented to support this hypothesis. In addition, a number of other strategies are tested to rule out other possible explanations of the success. Preliminary results are shown indicating that extensions of the proposed algorithm can give similar improvements on other hard optimisation problems
Branching fraction and CP asymmetry of the decays B+→K0Sπ+ and B+→K0SK+
No full textAn analysis of B+ → K0
Sπ+ and B+ → K0
S K+ decays is performed with the LHCb experiment. The pp
collision data used correspond to integrated luminosities of 1 fb−1 and 2 fb−1 collected at centre-ofmass
energies of
√
s = 7 TeV and
√
s = 8 TeV, respectively. The ratio of branching fractions and the
direct CP asymmetries are measured to be B(B+ → K0
S K+
)/B(B+ → K0
Sπ+
) = 0.064 ± 0.009 (stat.) ±
0.004 (syst.), ACP(B+ → K0
Sπ+
) = −0.022 ± 0.025 (stat.) ± 0.010 (syst.) and ACP(B+ → K0
S K+
) =
−0.21 ± 0.14 (stat.) ± 0.01 (syst.). The data sample taken at
√
s = 7 TeV is used to search for
B+
c
→ K0
S K+ decays and results in the upper limit ( fc · B(B+
c
→ K0
S K+
))/( fu · B(B+ → K0
Sπ+
)) <
5.8 × 10−2 at 90% confidence level, where fc and fu denote the hadronisation fractions of a ¯b
quark
into a B+
c or a B+ meson, respectively
Measurement of the time-dependent CP asymmetry in B0 -> J/ψ KS0 decays
No full textThis Letter reports a measurement of the CP violation observables SJ/ψK0S and CJ/ψK0S in the decay channel B0→J/ψK0S performed with 1.0 fb−1 of pp collisions at s√=7 TeV collected by the LHCb experiment. The fit to the data yields SJ/ψK0S=0.73±0.07(stat)±0.04(syst) and CJ/ψK0S=0.03±0.09(stat)±0.01(syst). Both values are consistent with the current world averages and within
expectations from the Standard Model
Measurement of the CP-violating phase \phi s in Bs->J/\psi\pi+\pi- decays
No full textMeasurement of the mixing-induced CP-violating phase phi_s in Bs decays is of prime importance in probing new physics. Here 7421 +/- 105 signal events from the dominantly CP-odd final state J/\psi pi+ pi- are selected in 1/fb of pp collision data collected at sqrt{s} = 7 TeV with the LHCb detector. A time-dependent fit to the data yields a value of phi_s=-0.019^{+0.173+0.004}_{-0.174-0.003} rad, consistent with the Standard Model expectation. No evidence of direct CP violation is found
A study of CP violation in B±→DK±B±→DK± and B±→Dπ±B±→Dπ± decays with D→KS0K±π∓ final states
No full textA first study of CP violation in the decay modes B± → [K0S K ±π∓]Dh± and B± → [K0S K ∓π±]Dh±, where h labels a K or π meson and D labels a D0 or D0 meson, is performed. The analysis uses the LHCb data set collected in pp collisions, corresponding to an integrated luminosity of 3 fb−1. The analysis is sensitive to the CP-violating CKM phase γ through seven observables: one charge asymmetry in each of the four modes and three ratios of the charge-integrated yields. The results are consistent with measurements of γ using other decay modes
Complexity of Max-SAT using stochastic algorithms
No full textHill-climbing has been shown to be more effective than exhaustive search in solving satisfiability problems. Also, it has been used either by itself or in combination with other methods to solve the most difficult region of SAT, the phase transition. We show that hill-climbing also finds SAT problems difficult around the phase transition. It too follows an easy-hard-eays transition
Diaphragmatic mobility in children with spastic cerebral palsy and differing motor performance levels
No full textThe aim of this study was to compare diaphragmatic mobility (DM)and respiratory function between children with cerebral palsy (CP)and healthy controls (HC). CP was divided into non-ambulatory CP (NACP)and ambulatory CP (ACP). Eighteen children with NACP, 18 with ACP and 18 HC age between 8 and 18 years were recruited. Ultrasound was used to measure DM on both sides. Respiratory muscle strength (RMS), pulmonary function (PF)and chest expansion (CE)were also measured. The results showed that there was significantly lower right DM in CP than HC group. The NACP group had significantly lower DM than the ACP group. There were also significantly lower values of RMS, PF and CE in CP, compared to the HC group. There are significant impairments of diaphragmatic and respiratory function in CP, relative to HC. Thus, appropriate interventions to improve diaphragmatic muscle strength are necessary for children with CP, especially in the NACP.</p
Effectiveness of the manual diaphragmatic stretching technique on respiratory function in cerebral palsy: A randomised controlled trial
No full textBackground: respiratory failure resulting from diaphragmatic muscle weakness is a major cause of long-term hospitalization in children with cerebral palsy (CP). Manual diaphragmatic stretching technique (MDST) can be directly applied to stretch diaphragmatic muscle and has been reported to improve respiratory function in patients with asthma and COPD. However, there have been no studies among CP. This study aimed to examine the effects of a six-week MDST course on respiratory function among CP. Methods: fifty-three children with spastic CP were randomly assigned to experimental (n = 27) and control (n = 26) groups. The experimental group received MDST on non-consecutive days, three days per week for six weeks alongside standard physiotherapy (SDPT), while the control group received only SDPT. The outcome variables were diaphragmatic mobility, pulmonary function and chest wall expansion. Results: MDST significantly improved diaphragmatic mobility on both sides of the body, with a between-group difference of 0.97 cm (95% CI 0.55–1.39 cm, p < 0.001) for the right side and 0.82 cm (95% CI 0.35–1.29 cm, p = 0.001) for the left side. MDST significantly improved chest wall expansion at the xiphoid process and umbilical levels, with between-group differences of 0.57 cm (95% CI 0.12–1.20 cm, p = 0.013) and 0.87 cm (95% CI 0.31–1.43 cm, p = 0.003), respectively. There was no significant difference in pulmonary function testing between the groups. Conclusion: MDST could significantly improve diaphragmatic mobility, and lower and abdominal chest wall expansion, among children with CP. Therefore, MDST could be considered as an additional technique for physiotherapy programmes, to improve diaphragmatic function in spastic CP.</p
Measurement of the CP-violating phase phi(s) in (B)over-bar(s)(0) -> J / psi pi(+)pi(-) decays
No full textThe mixing-induced CP -violating phase ϕs in View the MathML source and View the MathML source decays is measured using the J/ψπ+π− final state in data, taken from 3 fb−1 of integrated luminosity, collected with the LHCb detector in 7 and 8 TeV centre-of-mass pp collisions at the LHC. A time-dependent flavour-tagged amplitude analysis, allowing for direct CP violation, yields a value for the phase ϕs=70±68±8 mrad. This result is consistent with the Standard Model expectation and previous measurements
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