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Metamaterials are typically engineered by arranging a set of small scatterers or apertures in a regular array throughout a region of space, thus obtaining some desirable bulk electromagnetic behavior. The desired property is often one that is not normally found naturally (negative refractive index, near-zero index, etc.). Over the past ten years, metamaterials have moved from being simply a theoretical concept to a field with developed and marketed applications. Three-dimensional metamaterials can be extended by arranging electrically small scatterers or holes into a two-dimensional pattern at a surface or interface. This surface version of a metamaterial has been given the name metasurface (the term metafilm has also been employed for certain structures). For many applications, metasurfaces can be used in place of metamaterials. Metasurfaces have the advantage of taking up less physical space than do full three-dimensional metamaterial structures; consequently, metasurfaces offer the possibility of less-lossy structures. In this overview paper, we discuss the theoretical basis by which metasurfaces should be characterized, and discuss their various applications. We will see how metasurfaces are distinguished from conventional frequency-selective surfaces. Metasurfaces have a wide range of potential applications in electromagnetics (ranging from low microwave to optical frequencies), including: (1) controllable “smart” surfaces, (2) miniaturized cavity resonators, (3) novel wave-guiding structures, (4) angular-independent surfaces, (5) absorbers, (6) biomedical devices, (7) terahertz switches, and (8) fluid-tunable frequency-agile materials, to name only a few. In this review, we will see that the development in recent years of such materials and/or surfaces is bringing us closer to realizing the exciting speculations made over one hundred years ago by the work of Lamb, Schuster, and Pocklington, and later by Mandel'shtam and Veselago.

Abstract. This article, the second in the series, presents kinetic and photochemical data evaluated by the IUPAC Subcommittee on Gas Kinetic Data Evaluation for Atmospheric Chemistry. It covers the gas phase and photochemical reactions of Organic species, which were last published in 1999, and were updated on the IUPAC website in late 2002, and subsequently during the preparation of this article. The article consists of a summary table of the recommended rate coefficients, containing the recommended kinetic parameters for the evaluated reactions, and eight appendices containing the data sheets, which provide information upon which the recommendations are made.

Tables and graphs of the photon mass attenuation coefficient p/p and the mass energy-absorption coefficient p en /p are presented for all of the elements Z = 1 to 92, and for 48 compounds and mixtures of radiological interest. The tables cover energies of the photon (x ray, gamma ray, bremsstrahlung) from 1 keV to 20 MeV. The p/p values are taken from the current photon interaction database at the National Institute of Standards and Technology, and the p en /p values are based on the new calculations by Seltzer described in Radiation Research 136, 147 (1993). These tables of p/p and p en /p replace and extend the tables given by

Abstract. This article, the first in the series, presents kinetic and photochemical data evaluated by the IUPAC Subcommittee on GasKinetic Data Evaluation for Atmospheric Chemistry. It covers the gas phase and photochemical reactions of Ox, HOx, NOx and SOx species, which were last published in 1997, and were updated on the IUPAC website in late 2001. The article consists of a summary sheet, containing the recommended kinetic parameters for the evaluated reactions, and five appendices containing the data sheets, which provide information upon which the recommendations are made.

Abstract A necessary criterion for brittle fracture in crystals is established, in terms of the spontaneous emission of dislocations from an atomically sharp cleavage crack. We have calculated the stability of a sharp crack against emission of a blunting dislocation for a number of crystals and crystal types in two dimensions and the energy to form a stable loop of dislocation from the crack tip in three dimensions. We find that contrary to previous expectations, an atomically sharp cleavage crack is stable in a wide range of crystal types, but that in the face centred cubic metals investigated, blunting reactions occur spontaneously. Of the body centred metals investigated, iron is an intermediate case between the brittle and ductile cases, and the ionic and covalent crystals investigated are all stable against dislocation emission. Qualitatively, we find that crystals whose dislocations have wide cores, and small values of the parameter μb/γ (μb/γ⋦7·5 to 10) are ductile while crystals with narrow cores and large values of μb/r are brittle.

Ten conditions of trust were suggested by 84 interviews of managers, and two previous studies of managerial trust. Statements made in the interviews and the studies were used to develop a content theory of trust conditions and derive scales measuring them. The scales were generated with an iterative procedure using a total of 1531 management students. The scales were assessed for homogeneity, reliability, and validity with several samples: 180 managers and 173 of their subordinates, 111 machine operators, and four different samples of management students (n = 380, n = 129, n = 290, and n = 132). Construct validity was supported by showing that the scale measures behaved as hypothesized with respect to measures of other variables, a manipulation of expectations, and the reciprocity of trust in vertical dyads.

A bstract In accordance with experience concerning the behavior of glass at temperatures within its annealing range, an equation is proposed which relates the various extraordinary heat effects to the inelastic deformability and to the degree of superheating or undercooling. By using this equation in connection with the thermal‐expansion curves of a glass within its annealing range, certain constants that are related to the coefficient of viscosity and its changes with temperature and the degree of superheating or undercooling have been determined with reasonable results. Such results make it possible to estimate the inelastic deformability of a glass in its various conditions at all annealing temperatures and are therefore valuable in connection with problems that are encountered in the process of annealing glass. The apparent success achieved in applying the proposed equation to experimental data suggests that the concepts underlying this equation are fundamental and must be considered in any theory concerning the constitution of glass or that of any other extremely viscous liquid.

In this paper we introduce the minimum-order approach to frequency assignment and present a theory which relates this approach to the traditional one. This new approach is potentially more desirable than the traditional one. We model assignment problems as both frequency-distance constrained and frequency constrained optimization problems. The frequency constrained approach should be avoided if distance separation is employed to mitigate interference. A restricted class of graphs, called disk graphs, plays a central role in frequency-distance constrained problems. We introduce two generalizations of chromatic number and show that many frequency assignment problems are equivalent to generalized graph coloring problems. Using these equivalences and recent results concerning the complexity of graph coloring, we classify many frequency assignment problems according to the "execution time efficiency" of algorithms that may be devised for their solution. We discuss applications to important real world problems and identify areas for further work.

The authors report a repeated measures field study that captures complaining customers' perceptions of their overall satisfaction with the firm, likelihood of word-of-mouth recommendations, and repurchase intent during a 20-month span that includes two service failures and recovery attempts. The findings suggest that though satisfactory recoveries can produce a “recovery paradox” after one failure, they do not trigger such paradoxical increases after two failures. Furthermore, “double deviations” can occur following two consecutive unsatisfactory recoveries or following an unsatisfactory recovery in response to a second failure. The findings indicate that customers reporting an unsatisfactory recovery followed by a satisfactory recovery reported significantly higher ratings at the second postrecovery period than did customers reporting the opposite recovery sequence. The outcome of the second recovery also demonstrated a significant influence on customer ratings (positively if the recovery was satisfactory, negatively if the recovery was unsatisfactory), regardless of whether the customer found the first recovery satisfactory or unsatisfactory. In addition, although the increased change in recovery expectations and failure severity ratings from the first failure to the second is more dramatic for customers who previously reported a satisfactory recovery, the increase in attributions of blame toward the firm is more pronounced for customers who previously reported an unsatisfactory recovery. Last, the results show that recovery efforts are attenuated when two similar failures occur and when two failures happen in close time proximity.

The ionization produced by individual fast charged particles is frequently used as a measure of their initial energy; fluctuation effects set a theoretical limit to the accuracy of this method. Formulas are derived here to estimate the statistical fluctuations of the number of ions produced by constant amounts of radiation energy. The variance of the number of ionizations is found to be two or three times smaller than if this number were governed by a Poisson distribution. An improved understanding is gained of the statistical treatment of fluctuation phenomena.

This report evaluates lignin’s role as a renewable raw material resource. Opportunities that arise from utilizing lignin fit into one of three categories: 1)power, fuel and syngas (generally near-term opportunities) 2) macromolecules (generally medium-term opportunities) 3) aromatics and miscellaneous monomers (long-term opportunities). Biorefineries will receive and process massive amounts of lignin. For this reason, how lignin can be best used to support the economic health of the biorefinery must be defined. An approach that only considers process heat would be shortsighted. Higher value products present economic opportunities and the potential to significantly increase the amount of liquid transportation fuel available from biomass. In this analysis a list of potential uses of lignin was compiled and sorted into “product types” which are broad classifications (listed above as power—fuel—syngas; macromolecules; and aromatics). In the first “product type” (power—fuel—gasification) lignin is used purely as a carbon source and aggressive means are employed to break down its polymeric structure. In the second “product type” (macromolecules) the opposite extreme is considered and advantage of the macromolecular structure imparted by nature is retained in high-molecular weight applications. The third “product type” (aromatics) lies somewhere between the two extremes and employs technologies that would break up lignin’s macromolecular structure but maintain the aromatic nature of the building block molecules. The individual opportunities were evaluated based on their technical difficulty, market, market risk, building block utility, and whether a pure material or a mixture would be produced. Unlike the “Sugars Top 10” report it was difficult to identify the ten best opportunities, however, the potential opportunities fell nicely into near-, medium- and long-term opportunities. Furthermore, the near-, medium- and long-term opportunities roughly align with the three “product types.” From this analysis a list of technical barriers was developed which can be used to identify research needs. Lignin presents many challenges for use in the biorefinery. Chemically it differs from sugars having a complex aromatic substructure. Unlike cellulose, which has a relatively simple substructure of glucose subunits, lignin has a high degree of variability in its structure which differs both from biomass source and from the recovery process used. In addition to its variability lignin is also reactive and to some degree less stable thermally and oxidatively to other biomass streams. What this means is that integrating a lignin process stream within the biorefinery will require identifying the best method to separate lignin from biomass cost-effectively.

This paper introdLlces the normal probability plot correlation coefficient as a test statistic in complete samples for the composite hypothesis of normality. The proposed test statistic is conceptnally simple, is compntationally convenient, and is readily extendible to testing non-normal distributional hypotheses. An empirical power strldy shows that the normal probability plot correlation coefficient, compares favorably with 7 other normal test statistics. Percent points are tabulated for n = 3(l)50(5)100.

Most man-made and natural electromagnetic interference, or "noise," are highly non-Gaussian random processes, whose degrading effects on system performance can be severe, particularly on most conventional systems, which are designed for optimal or near optimal performance against normal noise. In addition, the nature, origins, measurement, and prediction of the general EM interference environment are a major concern of any adequate spectral management program. Accordingly, this study is devoted to the development of analytically tractable, experimentally verifiable, statistical-physical models of such electromagnetic interference. Here, classification into three major types of noise is made: Class A (narrow band vis-á-vis the receiver), Class B (broad band vis-á-vis the receiver), and Class C (= Class A + Class B). First-order statistical models are constructed for the Class A and Class B cases. In particular, the APD (a posteriori probability distribution) or exceedance probability, PD, vis;P1 (ϵ > ϵo)A,B, (and the associated probability densities, pdf's w1(ϵ)A,B,[1]) of the envelope are obtained; (the phase is shown to be uniformly distributed in (0, 2π). These results are canonical, i.e., their analytic forms are invariant of the particular noise source and its quantifying parameter values, levels, etc. Class A interference is described by a 3-parameter model, Class B noise by a 6-parameter model.

The viewpoint of the subject of matroids, and related areas of lattice theory, has always been, in one way or another, abstraction of algebraic dependence or, equivalently, abstraction of the incidence relations in geometric representations of algebra. Often one of the main derived facts is that all bases have the same cardinality. (See Van der Waerden, Section 33.) From the viewpoint of mathematical programming, the equal cardinality of all bases has special meaning — namely, that every basis is an optimum-cardinality basis. We are thus prompted to study this simple property in the context of linear programming. It turns out to be useful to regard “pure matroid theory”, which is only incidentally related to the aspects of algebra which it abstracts, as the study of certain classes of convex polyhedra. (1) A matroid M = (E,F) can be defined as a finite set E and a nonempty family F of so-called independent subsets of E such that (a) Every subset of an independent set is independent, and (b) For every A ⊆ E, every maximal independent subset of A, i.e., every basis of A, has the same cardinality, called the rank, r(A), of A (with respect to M). (This definition is not standard. It is prompted by the present interest). (2) Let RE denote the space of real-valued vectors x = [xj], j ∈ E. Let R+E = {x: 0 ≤ x ∈ RE}. (3) A polymatroid P in the space RE is a compact non-empty subset of R+E such that (a) 0 ≤ x0 ≤ x1 ∈ P = ⇒ x0 ∈ P. (b) For every a ∈ R+E, every maximal x ∈ P such that x ≤ a, i.e., every basis x of a, has the same sum j∈E xj, called the rank, r(a), of a (with respect to P).

The mechanics of lateral crack propagation in a sharp‐indenter contact field are described. The driving force for fracture has its origin in the residual component of the elastic/plastic field, which becomes dominant as the indenter is unloaded. Expressions for equilibrium crack evolution are derived, with due allowance for the close proximity of crack plane and specimen free surface. As with the median/radial crack system considered in an earlier paper, the ratio hardness‐to‐modulus complements toughness in the fracture relations. The basic predictions of the theory are examined in terms of experimental measurements of lateral crack dimensions in materials with a wide range of mechanical properties. The prospects of predicting the extent of lateral fracture in other ceramics, and thence of establishing a base for analyzing such important practical properties as surface erosion, are discussed.

Basic meteorological concepts are covered as well as plume rise, source effects, and diffusion models. Chapters are included on cooling tower plumes and urban diffusion. Suggestions are given for calculating diffusion in special situations, such as for instantaneous releases over complex terrain, over long distances, and during times when chemical reactions or dry or wet deposition are important. (PSB)

A method of blvariate interpolation and smooth surface fitting is developed for z values given at points irregularly distributed in the x-y plane. The interpolating function is a fifth-degree polynomial in x and y defined in each triangular cell whmh has projections of three data points in the x-y plane as its vertexes. Each polynomial is determined by the given values of z and estimated values of partial derivatives at the vertexes of the triangle. Procedures for dividing the x-y plane into a number of triangles, for estimating partial derivatives at each data point, and for determining the polynomial in each triangle are described A simple example of the application of the proposed method is shown.

This paper derives generalized sheet transition conditions (GSTCs) for the average electromagnetic fields across a surface distribution of electrically small scatterers characterized by electric and magnetic polarization densities. We call such an arrangement of scatterers a metafilm-the two-dimensional (2-D) equivalent of a metamaterial. The derivation is based on a replacement of the discrete distribution of scatterers by a continuous one, resulting in a continuous distribution of electric and magnetic polarization densities in the surface. This is done in a manner analogous to the Clausius-Mossotti-Lorenz-Lorentz procedure for determining the dielectric constant of a volume distribution of small scatterers. The result contains as special cases many particular ones found throughout the literature. The GSTCs are expected to have wide application to the design and analysis of antennas, reflectors, and other devices where controllable scatterers are used to form a "smart" surface.

ITL) at the National Institute of Standards and Technology (NIST) promotes the U.S. economy and public welfare by providing technical leadership for the Nation's measurement and standards infrastructure. ITL develops tests, test methods, reference data, proof of concept implementations, and technical analyses to advance the development and productive use of information technology. ITL's responsibilities include the development of technical, physical, administrative, and management standards and guidelines for the cost-effective security and privacy of sensitive unclassified information in Federal computer systems.

A straightforward approach that does not involve delta-function techniques is used to rigorously derive a generalized electric dyadic Green's function which defines uniquely the electric field inside as well as outside the source region. The electric dyadic Green's function, unlike the magnetic Green's function and the impulse functions of linear circuit theory, requires the specification of two dyadics: the conventional dyadic G <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</inf> outside its singularity and a source dyadic L <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> which is determined solely from the geometry of the "principal volume" chosen to exclude the singularity of G <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</inf> . The source dyadic L <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> is characterized mathematically, interpreted physically as a generalized depolarizing dyadic, and evaluated for a number of principal volumes (self-cells) which are commonly used in numerical integration or solution schemes. Discrepancies at the source point among electric dyadic Green's functions derived by a number of authors are shown to be explainable and reconcilable merely through the proper choice of the principal volume. Moreover, the ordinary delta-function method, which by itself is shown to be inadequate to extract uniquely the proper electric dyadic Green's function in the source region, can be supplemented by a simple procedure to yield unambiguously the correct Green's function representation and associated fields.