Experimental analysis of true left-handed behaviour and transmission properties of composite metamaterials

We report the true left-handed transmission of a composite metamaterial (CMM) consisting of periodically stacked split-ring resonator (SRR) and wire elements. The negative permeability (μ < 0) gap is demonstrated explicitly by comparing SRR and closed-ring resonator structures. We confirm experimentally that the plasma cut-off frequency of the CMM is determined by the combined dielectric response of SRR and wire elements, and it is much lower than that of the wire-only medium. This is crucial to identify the left-handed transmission bands of the CMM. We further investigate the effect of intralayer and interlayer disorder on the transmission spectrum of CMM arising from misaligned fabrication and stacking of the SRR layers. We found that the intralayer disorder affects the μ < 0 gap of SRRs and the left-handed transmission band of CMM significantly, whereas the SRR transmission is rather immune to interlayer disorder.     

Quasi-static and dynamic loading responses and constitutive modeling of titanium alloys

The results from a systematic study of the response of a Ti–6Al–4V alloy under quasi-static and dynamic loading, at different strain rates and temperatures, are presented. The correlations and predictions using modified Khan–Huang–Liang (KHL) viscoplastic constitutive model are compared with those from Johnson–Cook (JC) model and experimental observations for this strain rate and temperature-dependent material. Overall, KHL model correlations and predictions are shown to be much closer to the observed responses, than the corresponding JC model predictions and correlations. Similar trend has been demonstrated for other titanium alloys using published experimental data [Mech. Mater. 33(8) (2001) 425; J. Mech. Phys. Solids 47(5) (1999) 1157].     

Dynamic stress equilibration in split Hopkinson pressure bar tests on soft materials

The condition of dynamic stress equilibrium is not satisfied automatically when a split Hopkinson pressure bar (SHPB) is employed to determine the dynamic properties of soft materials. In order to develop guidelines for the proper design of SHPB experiments under valid testing conditions, an integrated experimental/analytical study has been conducted to examine the process of dynamic stress equilibrium in a soft rubber specimen. Dynamic compressive experiments on a RTV 630 and an ethylene-propylene-diene monomer rubber with a SHPB modified for soft material testing were conducted to determine the effects of specimen thickness and loading rate on the stress equilibrating process. An analytical model was employed to analyze the equilibrating processes observed in experiments. It is found that the incident loading rate dominates the initial non-equilibrium stress state, and the specimen thickness mainly affects the dynamic stress equilibrium after the initial stage.     

MAC protocol with delay-aware adaptive round time for split light-trail

Light-trail (LT) has been considered as an attractive solution for optical networks to support emerging services such as video-on-demand, pseudo-wires, and data-centers. The media access control (MAC) protocol is essential for LT networks because LT is a shared-medium. Recently, in order to enhance the throughput, a regular LT can be split into several sub-LTs at the split nodes where traffic undergoes optical-electronic-optical conversation. To deal with the split LT, a novel MAC protocol named Delay-aware adaptive round time for split LT (DAARTS) is developed on the basis of DAART MAC protocol and the schemes of splitting LT. To estimate the performance of the developed MAC protocol, ART, DAART and DAARTS protocols are simulated and compared in the scenarios of three different traffic patterns. Simulation results show that, for traffic 1 and traffic 2, DAARTS has stable throughput performance and can obtain almost 40.83% and 106.64% throughput improvement compared with DAART, respectively. In other words, DAARTS can further enhance the throughput of LT networks.     

A new,reliable family of split-operator methods for computing reacting flows

A new, reliable family of split-operator methods is presented for the computation of reacting flows. The methods may be inconsistent or consistent depending upon their applicability. Analyses are carried out for flow combusting according to general multicomponent, multireaction linear or non-linear chemical kinetic models, and conditions for guaranteed stability/convergence are established. A special chemical splitting parameter can also be embedded in the methods enabling accelerated convergence of an iterative finite-difference solution. Computed results highlight the capabilities and properties of the methods.     

Optimization of conditions for high temprature capillarary gas chromatography using a split-mode programmable temprature vaporizing injection system

This paper discribes an investigation into the effects of various operating conditions applied in a PTV-based gas chromatographic system on the performance observed in high temperature analyses. The work comprises a combination of physical and chromatographic measurements, and conclusions are drawn as to the most effective way of using the equipment under evaluation.     

Fractional weak discrepancy and split semiorders

The fractional weak discrepancywd_F(P) of a poset P=(V,?) was introduced in Shuchat et al. (2007) [6] as the minimum nonnegative k for which there exists a function f:V→R satisfying (i) if a?b then f(a)+1≤f(b) and (ii) if a∥b then |f(a)−f(b)|≤k. In this paper we generalize results in Shuchat et al. (2006, 2009) [5] and [7] on the range of wd_F for semiorders to the larger class of split semiorders. In particular, we prove that for such posets the range is the set of rationals that can be represented as r/s for which 0≤s−1≤r<2s.     

On the facets of the secondary polytope

The secondary polytope of a point configuration A is a polytope whose face poset is isomorphic to the poset of all regular subdivisions of A. While the vertices of the secondary polytope - corresponding to the triangulations of A - are very well studied, there is not much known about the facets of the secondary polytope.The splits of a polytope, subdivisions with exactly two maximal faces, are the simplest examples of such facets and the first that were systematically investigated. The present paper can be seen as a continuation of these studies and as a starting point of an examination of the subdivisions corresponding to the facets of the secondary polytope in general. As a special case, the notion of k-split is introduced as a possibility to classify polytopes in accordance to the complexity of the facets of their secondary polytopes. An application to matroid subdivisions of hypersimplices and tropical geometry is given.     

On mixed-integer sets with two integer variables

We show that every facet-defining inequality of the convex hull of a mixed-integer polyhedral set with two integer variables is a crooked cross cut (which we defined in 2010). We extend this result to show that crooked cross cuts give the convex hull of mixed-integer sets with more integer variables if the coefficients of the integer variables form a matrix of rank 2. We also present an alternative characterization of the crooked cross cut closure of mixed-integer sets similar to the one on the equivalence of different definitions of split cuts presented in Cook et al. (1990) [4]. This characterization implies that crooked cross cuts dominate the 2-branch split cuts defined by Li and Richard (2008) [8]. Finally, we extend our results to mixed-integer sets that are defined as the set of points (with some components being integral) inside a closed, bounded and convex set.