Perfect impedance-matched left-handed behavior in combined metamaterial

Matching the impedance of a medium to free space, which is usually not available in natural materials, is an important advance in metamaterials. In this paper, we present a simple mechanism for a perfect impedance-matched left-handed metamaterials, that reveals a nearly zero reflection over operating frequency. This finding is based on the independent manipulation of the electric response without any effect on the magnetic one.     

Absolute exponential stability criteria for a class of nonlinear time-delay systems

This paper is concerned with the problem of absolute exponential stability analysis for a class of continuous-time systems with sector-bounded nonlinearities and interval time-varying delays. Absolute exponential stability criteria, which depend not only on the delay range but also on the decay rate, are derived by using a novel Lyapunov functional. These criteria are expressed in the form of linear matrix inequalities (LMIs) and they can easily be checked. By solving these LMIs, estimates of the exponential decay rate and decay coefficient are obtained. A numerical example is provided to demonstrate the effectiveness of the proposed method.     

A microscopic pedestrian-simulation model and its application to intersecting flows

We develop a microscopic pedestrian-simulation model in which pedestrian positions are updated at discrete time steps. At each time step, each pedestrian probabilistically selects a direction of movement from a predetermined set according to a logit-type function that considers the dynamics of other pedestrians around, and then selects a step size that satisfies a certain distribution. We perform a number of field experiments on real intersecting pedestrian flows with four different angles. We then validate and calibrate the model using sample data on the deviation angles, step velocities, and velocity–density relations obtained from the experiments.     

Triple negative permeability band in plasmon-hybridized cut-wire-pair metamaterials

We expand the picture of plasmon hybridization in metamagnetic structure via numerically studying the electromagnetic coupling in the metallic cut-wire-pair super cells. It is shown that a triple negative permeability band can be achieved by systematically controlling the plasmon hybridization in such the structure. The corresponding transmission properties as well as the electromagnetic responses of the plasmon-hybridized structures were presented by using the finite integration technique simulations. Our results would reveal a promising design to obtain the multiple negative refractions based on the combination of hybridized cut-wire-pairs and continuous wires.     

A multiple regression model for urban traffic noise in Hong Kong

This article describes the roadside traffic noise surveys conducted in heavily built-up urban areas in Hong Kong. Noise measurements were carried out along 18 major roads in 1999. The measurement data included L10, L50, L90, Leq, Lmax, the number of light vehicles, the number of heavy vehicles, the total traffic flow, and the average speed of vehicles. Statistical analysis using the analysis of variance (ANOVA) and Tukey test (p<0.05) reveals that the total traffic flow and the number of heavy vehicles are the most significant factors of urban traffic noise. Multiple regression was used to derive a set of empirical formulas for predicting L10 noise level due to road traffic. The accuracy of these empirical formulas is quantified and compared to that of another widely used prediction model in Hong Kong--the Calculation of Road Traffic Noise. The applicability of the selected multiple regression model is validated by the noise measurements performed in the winter of 2000.     

2,4,6-Tris(4-nitrophenoxy)-1,3,5-triazine: a hexagonal host framework stabilised by the NO2-trimer supramolecular synthon

The title molecule forms a honeycomb network of molecular and nitro-trimer synthons with guest species included in the hexagonal voids.     

Lattice Polytopes with Distinct Pair-Sums

Let P be a lattice polytope in R ⁿ , and let P \cap Z ⁿ = {v ₁ ,\ldots,v _N } . If the N + N\choose 2 points 2v ₁ ,\ldots, 2v _N ;v ₁ +v ₂ ,\ldots, v _N-1 + v _N are distinct, we say that P is a ``distinct pair-sum' or ``dps' polytope. We show that if P is a dps polytope in R ⁿ , then N≤ 2 ⁿ , and, for every n , we construct dps polytopes in R ⁿ which contain 2 ⁿ lattice points. We also discuss the relation between dps polytopes and the study of sums of squares of real polynomials. Received November 10, 2000, and in revised form June 28, 2001. Online publication November 2, 2001.