30,764 research outputs found
Chi-boundedness of graph classes excluding wheel vertex-minors
No full textA class of graphs is χ-bounded if there exists a function f:N→N such that for every graph G in the class and an induced subgraph H of G, if H has no clique of size q+1, then the chromatic number of H is less than or equal to f(q). We denote by Wn the wheel graph on n+1 vertices. We show that the class of graphs having no vertex-minor isomorphic to Wn is χ-bounded. This generalizes several previous results; χ-boundedness for circle graphs, for graphs having no W5 vertex-minors, and for graphs having no fan vertex-minors
Improved measurement of the branching fraction of h c → γη′/η and search for h c → γπ 0
No full textAbstract The processes h c → γP (P = η′, η, π 0) are studied with a sample of (27.12 ± 0.14) × 108 ψ(3686) events collected by the BESIII detector at the BEPCII collider. The decay h c → γη is observed for the first time with the significance of 9.0 σ, and the branching fraction is determined to be (3.77 ± 0.55 ± 0.13 ± 0.26) × 10 −4, while B (h c → γη′) is measured to be (1.40 ± 0.11 ± 0.04 ± 0.10) × 10 −3, where the first uncertainties are statistical, the second systematic, and the third from the branching fraction of ψ(3686) → π 0 h c . The combination of these results allows for a precise determination of R h c = B h c → γη B h c → γ η ′ , which is calculated to be (27.0 ± 4.4 ± 1.0)%. The results are valuable for gaining a deeper understanding of η − η′ mixing, and its manifestation within quantum chromodynamics. No significant signal is found for the decay h c → γπ 0, and an upper limit is placed on its branching fraction of B (h c → γπ 0) < 5.0 × 10 −5, at the 90% confidence level
Design of planar inverted-F antennas (PIFA) for multiband wireless applications
No full textA small three bands printed inverted-F antenna with independently controlling the resonant frequency is presented. The proposed antenna consists of two arms
supported by shorting walls fed by 50 Ω microstrip transmission line and a ground plane. The antenna occupied a compact size of 26 x 25 x 3.75 mm. The main radiated patch
injected with slot and another arm to generate and control the three resonant frequencies to cover 2.4, 3.7 and 5.2GHz
Wireless Local Area Network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX). The simulated and measured results show that the antenna achieves a gain of 2, 3 and 5 dBi respectively and radiation efficiency of 50%, 60% and 85% for the three bands respectively. The simulated and measured result for the return loss is in good agreements
Figure 5 from: Bakalin V, Choi SS, Park SJ (2021) Revision of Gymnomitriaceae (Marchantiophyta) in the Korean Peninsula. PhytoKeys 176: 77-110. https://doi.org/10.3897/phytokeys.176.62552
No full textFigure 5 Marsupella tubulosa Steph. A gynoecium longitudinal section B stem cross section (fragment) C plant habit, dorsal view D leaf margin cells E, F leaves G elater, H midleaf cells. Scale bars: 1 mm (A, C, E, F); b 100 µm (B, D, G, H). All from Choi 3732 (JNU)
Online Ramsey theory for a triangle on F‐free graphs
No full textGiven a class of graphs and a fixed graph H, the online
Ramsey game for H on is a game between two players
Builder and Painter as follows: an unbounded set of
vertices is given as an initial state, and on each turn Builder
introduces a new edge with the constraint that the resulting
graph must be in , and Painter colors the new edge either
red or blue. Builder wins the game if Painter is forced to
make a monochromatic copy of H at some point in the
game. Otherwise, Painter can avoid creating a monochromatic
copy of H forever, and we say Painter wins the game.
We initiate the study of characterizing the graphs F such
that for a given graph H, Painter wins the online Ramsey
game for H on F‐free graphs. We characterize all graphs F
such that Painter wins the online Ramsey game for C3 on
the class of F‐free graphs, except when F is one particular
graph. We also show that Painter wins the online Ramsey
game forC3 on the class of K4‐minor‐free graphs, extending
a result by Grytczuk, Hałuszczak, and Kierstead [Electron.
J. Combin. 11 (2004), p. 60]. © 2019 Wiley Periodicals, Inc.11Nsci
Operator upper bounds for Davis-Choi-Jensen's difference in Hilbert spaces
No full textIn this paper we obtain several operator inequalities providing upper bounds for the Davis-Choi-Jensen's Difference Ph (f (A)) - f (Ph (A)) for any convex function f : I → R, any selfadjoint operator A in H with the spectrum Sp (A) ⊂ I and any linear, positive and normalized map Ph : B (H) → B (K), where H and K are Hilbert spaces. Some examples of convex and operator convex functions are also provided
Liner for Shaped-Charge Munitions
No full textIn 1977 three National Bureau of Standards (NBS) resident guest scientists from the Army Picatinny Arsenal (Henry J. Prask, Chang-Sun Choi, and Sam F. Trevino) used the neutron diffraction facilities at the NBS Research Reactor to make the first non-destructive characterization of texture as a function of depth in a metallurgical specimen. This and related work by the Army group at the NBS Reactor showed that not only texture but also residual strains and stresses could be depth-profiled non-destructively using neutron diffraction. Residual strains and stresses add to externally-applied stresses, increasing or decreasing the effective strength of materials. Today every major neutron research center in the world has a neutron diffraction facility for determination of residual stress in engineering components using the technique pioneered by Prask, Choi, and Trevino. While originally this technique was used to study the properties of shaped-charge munitions for the Army (this copper liner for a Shaped-Charge Munitions was used in their NBS experiments, but never received neutron exposure), the technique is now commonly used for many civilian applications including: The effect on stresses of bending welded vs. extruded tubing; characterization of stresses resulting from different methods of railroad-rail fabrication; characterization of stresses around welds in railroad tank cars carrying hazardous materials; determination of changes in residual stresses in induction-hardened auto-axles and the correlation with fatigue life; characterization of stresses in a ring/plug primary standard for testing other stress-measurement techniques; characterization of residual stresses in aircraft components; characterization of stresses to improve welding technology; determination of stresses in thermal-spray coatings; confirmation of stress relief by the ultrasonic impact method; characterization of stresses produced by a new welding technique: Friction Stir Welding; reducing spring-back stresses in stamped sheet metal for automobiles; residual stresses in new composites; residual stress measurement in coil, linepipe and girth welded pipe.10 x 10 x 10 c
Uncertainty based MDO of UAS using HAPMOEA
No full textCFD has been successfully used in the optimisation of aerodynamic surfaces using a given set of parameters such as Mach numbers and angle of attack. While carrying out a multidisciplinary design optimisation one deals with situations where the parameters have some uncertain attached. Any optimisation carried out for fixed values of input parameters gives a design which may be totally unacceptable under off-design conditions. The challenge is to develop a robust design procedure which takes into account the fluctuations in the input parameters. In this work, we attempt this using a modified Taguchi approach. This is incorporated into an evolutionary algorithm with many features developed in house. The method is tested for an UCAV design which simultaneously handles aerodynamics, electromagnetics and maneuverability. Results demonstrate that the method has considerable potential. \u
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