bluuebunny/crossref_metadata_2025 huggingface dataset:
Polyphosphate‐fertilizer solution stability with time, temperature, and pH
Authors: McBeath Therese M. , Lombi Enzo , McLaughlin Michael J. , Bünemann Else K.
Published: May 2007

Ammonium polyphosphate fertilizers are gaining popularity in agricultural industry due to ease of application and yield benefits in calcareous soils. In this study, the effects of temperature, pH, and time on the stability of ammonium polyphosphate–fertilizer solution simulating a range of storage conditions were evaluated. Ion chromatography was used for the speciation of orthophosphate, pyrophosphate, and tripolyphosphate in the polyphosphate‐fertilizer solution over time. Polyphosphate solutions were very stable when the pH was maintained close to neutral (pH 6.4) and the temperature was less than 25°C. In contrast, at the lowest pH (2.3) and highest temperature (50°C) almost all tripolyphosphate and 96% of pyrophosphate was hydrolyzed after 28 d. The hydrolysis rate constant for tripolyphosphate at 50°C was calculated to be 9.2 × 10–7 s–1 and the half‐life 20 d. At 25°C, the half‐life of tripolyphosphate was 34 d at pH 2.3 and 174 d at pH 5.4. The activation energy at pH 2.3 was 12.7 kJ mol–1. The results demonstrate that increasing temperature and decreasing pH have a deleterious effect on the stability of condensed P species in polyphosphate fertilizer. The effect of acidification on polyphosphate‐fertilizer composition requires consideration when formulating mixed ammonium polyphosphate blends with acids and trace elements for application in the field.
Application of feedback‐controlled pulse shaping for control of CARS spectra: the role of phase and amplitude modulation
Authors: Konradi J. , Scaria A. , Namboodiri V. , Materny A.
Published: May 2007

Femtosecond time‐resolved coherent anti‐Stokes Raman scattering (fs‐CARS) results in spectra that, as a function of the probe delay time, yield information about the dynamics of the coherently excited vibrational modes. A change of the shape of the exciting laser pulses has a dramatic influence on the spectral response. A feedback‐controlled optimization of specific modes making use of phase and amplitude modulation of the Stokes laser pulse is applied to selectively influence the anti‐Stokes signal spectrum. The role of phase and amplitude changes of the frequency components of the ultrashort pulse is analyzed. It can be demonstrated that the optimization process is clearly dominated by the effect of timing of the dispersed pulse segments. The modulation of the spectral amplitudes has only a small influence on the mode ratios. We conclude that mode focusing in time domain CARS spectroscopy can be achieved only by correctly setting the phases of the spectral pulse components (here demonstrated for the Stokes laser). Copyright © 2007 John Wiley & Sons, Ltd.
Water‐Based Polyurethane Filled with Multi‐Walled Carbon Nanotubes Prepared by a Colloidal‐Physics Method▪Author: This manuscript has been thoroughly edited. Please read the proofs carefully to ensure that no unintentional shift in meaning has been introduced.▪
Authors: Cai Dongyu , Song Mo
Published: May 2007

MWCNT/water‐based PU composites were synthesized by means of a colloidal‐physics method. The effect of MWCNT addition on the electrical and thermal properties of the composites and the effect of NaCl addition on film formation of the PU latexes were investigated. The electrical conductivity of the water‐based PU was improved by more than four orders of magnitude, but remained still four orders of magnitude lower than that of the MWCNTs. The percolation threshold was found to be at 0.5 wt.‐% MWCNT. The thermal conductivity of the composites was improved by ≈86% at 7 wt.‐% MWCNT. MWCNT/PU dispersions displayed stronger shear thinning than pure PU dispersions.

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Characterization of Polyaniline Nanotubes Formed in the Presence of Amino Acids
Authors: Zhang Lijuan , Peng Hui , Zujovic Zoran D. , Kilmartin Paul A. , Travas‐Sejdic Jadranka
Published: May 2007

Self‐assembled nanotubular structures of polyaniline were chemically synthesized from solutions containing different amino acids with the addition of ammonium persulfate as the oxidant. The materials were characterized by SEM and a range of spectroscopic methods. Spectroscopic characterizations revealed that the synthesized materials had many features typical of chemically synthesized PANI. Some additional features were also found and have been ascribed to non‐conducting material formed in the initial stages of the reaction at a higher solution pH. However, UV‐vis and 13C NMR spectra point toward a conductive material as the final product of the reaction. Cyclic voltammetry results also indicate an electroactive final product that closely resembles regular PANI in its electrochemical characteristics.

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EPR Identification of Zr(III) Complexes Formed upon Interaction of (2‐PhInd)2ZrCl2 and rac‐Me2Si(1‐Ind)2ZrCl2 with MAO and MMAO
Authors: Lyakin Oleg Y. , Bryliakov Konstantin P. , Panchenko Valentina N. , Semikolenova Nina V. , Zakharov Vladimir A. , Talsi Evgenii P.
Published: May 2007

Reactions of 1 and 2 with MAO and MMAO were monitored by EPR. It was found that MMAO is a stronger reducing agent than MAO. 1 is more prone to reduction than 2. The reduction of ZrIV to ZrIII seems to be the essential pathway of some zirconocene catalysts' deactivation. ZrIII species with the following proposed structures can be identified in the 1/MMAO system: (2‐PhInd)2ZrIII(iBu), (2‐PhInd)2ZrIII(µ‐Cl)2AliBu2, (2‐PhInd)2ZrIII(µ‐Cl)(iBu)AliBu2, and [(2‐PhInd)2ZrIII]+[Me‐MAO]−. The degree of reduction of ZrIV species determined by EPR in the catalytic system 2/MMAO can be masked by the formation of diamagnetic ZrIII/ZrIII dimers. Addition of monomers to the 2/MAO system promotes reduction ot the zirconium species.

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RECONSTRUCTION OF BINARY RELATIONS FROM THEIR RESTRICTIONS OF CARDINALITY 2, 3, 4 and (n ‐ 1) I
Authors: Lopez Gérard , Rauzy Claire
Published: May 2007

We prove that any binary relation with underlying set (base) E with cardinality n > 6 is reconstructible from its restrictions of cardinality 2, 3, 4 and (n ‐ 1). In part I we characterize relations R and R' on the same base E such that R/X and R'/X are isomorphic for every subset X of E with cardinality 2, 3, 4. In part II we shall prove that R and R' are isomorphic as soon as n > 6 when R/X and R/X' are isomorphic for every subset X of E with cardinality 2, 3, 4 and (n ‐ 1).
ITERATIONS OF SATISFACTION CLASSES AND MODELS OF PEANO ARITHMETIC
Authors: Murawski Roman
Published: May 2007

We consider iterations of satisfaction classes and apply them to construct expansions of models of Peano arithmetic to models of A|Δ+∑‐AC. 1991 MSC: 03F35, 03C62.
ON DEFINABILITY OF NORMAL SUBGROUPS OF A SUPERSTABLE GROUP
Authors: Tsuboi Akito
Published: May 2007

In this note we treat maximal and minimal normal subgroups of a superstable group and prove that these groups are definable under certain conditions. Main tool is a superstable version of Zil'ber's indecomposability theorem. MSC: 03C60.
LEVELS OF IMPLICATION AND TYPE FREE THEORIES OF CLASSIFICATIONS WITH APPROXIMATION OPERATOR
Authors: Cantini Andrea
Published: May 2007

We investigate a theory of Frege structures extended by the Myhill‐Flagg hierarchy of implications. We study its relation to a property theory with an approximation operator and we give a proof theoretical analysis of the basic system involved. MSC: 03F35, 03D60.
THE DECISION PROBLEM FOR RESTRICTED UNIVERSAL QUANTIFICATION IN SET THEORY AND THE AXIOM OF FOUNDATION
Authors: Parlamento Franco , Policriti Alberto
Published: May 2007

The still unsettled decision problem for the restricted purely universal formulae ((∀)0‐formulae) of the first order set‐theoretic language based over =, ∈ is discussed in relation with the adoption or rejection of the axiom of foundation. Assuming the axiom of foundation, the related finite set‐satisfiability problem for the very significant subclass of the (∀)0‐formulae consisting of the formulae involving only nested variables of level 1 is proved to be semidecidable on the ground of a reflection property over the hereditarily finite sets, and various extensions of this result are obtained. When variables are restricted to range only over sets, in universes with infinitely many urelements the set‐satisfiability problem is shown to be solvable provided the axiom of foundation is assumed; if it is not, then the decidability of a related derivability problem still holds. That, in turn, suggests the alternative adoption of an antifoundation axiom under which the set‐satisfiability problem is also solvable (of course with different answers). Turning to set theory without urelements, assuming a form of Boffa's antifoundation axiom, the complement of the set‐satisfiability problem for the full class of Δ0‐formulae is shown to be semidecidable; a result that is known not to hold, for the set‐satisfiability problem itself, even for a very restricted subclass of the Δ0‐formulae.
ON THE ITERATED ω‐RULE
Authors: Michalski Grzegorz
Published: May 2007

Let Γn(φ) be a formula of LPA (PA = Peano Arithmetic) meaning “there is a proof of φ from PA‐axioms, in which ω‐rule is iterated no more than n times”. We examine relations over pairs of natural numbers of the kind.

(n, k) ≦H (n', k') iff PA + RFNn' (Hk') ⊩ RFNn (Hk).

Where H denotes one of the hierarchies ∑ or Π and RFNn(C) is the scheme of the reflection principle for Γn restricted to formulas from the class C(Γn(φ) implies “φ is true”, for every φ ∈ C). Our main result is that.

(n, k) ≦H (n', k') if n ≦ n' and k ≦ max (k', 2n' + 1).
ANEW RELATION‐COMBINING THEOREM AND ITS APPLICATION
Authors: Sun Zhi‐Wei
Published: May 2007

Let ∃n denote the set of all formulas ∃x1…∃xn[P(x1, …,xn) = 0], where P is a polynomial with integer coefficients. We prove a new relation‐combining theorem from which it follows that if ∃n is undecidable over N, then ∃2n+2 is undecidable over Z.
ANALYTIC COMPLETENESS THEOREM FOR ABSOLUTELY CONTINUOUS BIPROBABILITY MODELS
Authors: Đorđević Radosav S.
Published: May 2007

Hoover [2] proved a completeness theorem for the logic L(∫)𝒜. The aim of this paper is to prove a similar completeness theorem with respect to product measurable biprobability models for a logic L(∫1, ∫2) with two integral operators. We prove: If T is a ∑1 definable theory on 𝒜 (a countable admissible set and ω ∈) and consistent with the axioms of L(∫1, ∫2), then there is an analytic absolutely continuous biprobability model in which every sentence in T is satified.
UNIVERSAL FUNCTIONS IN PARTIAL STRUCTURES
Authors: Negri Maurizio
Published: May 2007

In this work we show that every structure 𝒜 can be expanded to a partial structure 𝒜* with universal functions for the class of polynomials on 𝒜*. We can embed 𝒜* monomorphically in a total structure 𝒜º that preserves universal functions of 𝒜* and that is universal among such structures, i.e. 𝒜º can be homomorphically embedded in every total structure that preserves universal functions of 𝒜*. Universal functions are the starting point for developing recursion theoretic tools in an 𝒜* that satisfies some simple additional conditions.
A CLASS OF MODELS FOR SKALA'S SET THEORY
Authors: Greco Antonio
Published: May 2007

For each ordinal α it is given a model for Skala's set theory using the well‐known cumulative type hierarchy.
THE AMBIGUOUS TYPE THEORY IS HEREDITARILY UNDECIDABLE
Authors: Kuzichev Andrey A.
Published: May 2007

The ambiguous type theory ATT is introduced in [1] in order to obtain a new proof of Specker's theorem on typical ambiguity [3]. In the present paper we imbed the recursively undecidable theory TR of a single transitive‐reflexive relation in an arbitrary stratified theory T such that T ⫅ ATT and so reduce the problem of derivability in TR to the same problem for T. From this it follows that ATT is hereditarily undecidable, i.e. ATT has no decidable subtheories.
ON THE INCOMPLETENESS OF A DESCENDING CHAIN OF EXTENSIONS OF IMPLICATIONAL S5
Authors: Ulrich Dolph
Published: May 2007

C5.ω is obtained by adding, schematically, to the strict‐implicational fragment C5 of S5 the axiom ((p → q) → (q → p)) → (q → p). This paper presents a fully general proof that neither C5.ω nor any of a descending chain of its extensions is complete with respect to any class of frames, correcting the garbled details of a version skeched in an earlier paper (same Zeitschrift 31 (1985), 201‐208).
PARTIALLY ORDERED CONNECTIVES
Authors: Sandu Gabriel , Väänänen Jouko
Published: May 2007

We show that a coherent theory of partially ordered connectives can be developed along the same line as partially ordered quantification. We estimate the expressive power of various partially ordered connectives and use methods like Ehrenfeucht games and infinitary logic to get various undefinability results.
ON NON‐DETERMINED EHRENFEUCHT‐FRAÏSSÉ GAMES AND UNSTABLE THEORIES
Authors: Hyttinen Tapani , Hyttinen T.
Published: May 2007

In this paper we prove under some set theoretical assumptions that if T is a countable unstable theory then there is a pair of models of T such that Ehrenfeucht‐Fraïssé games between these models of large variety of lengths are non‐determined.
ON SOME INTERPRETATIONS OF CLASSICAL LOGIC
Authors: Boričić Branislav R. , Boričić B. R.
Published: May 2007

In distinction from the well‐known double‐negation embeddings of the classical logic we consider some variants of single‐negation embeddings and describe some classes of superintuitionistic first‐order predicate logics in which the classical first‐order calculus is interpretable in such a way. Also we find the minimal extensions of Heyting's logic in which the classical predicate logic can be embedded by means of these translations.
A FORMALISM FOR SOME CLASS OF FORCING NOTIONS
Authors: Koszmider Piotr , Koszmider P.
Published: May 2007

We introduce a class of forcing notions, called forcing notions of type S, which contains among other Sacks forcing, Prikry‐Silver forcing and their iterations and products with countable supports. We construct and investigate some formalism suitable for this forcing notions, which allows all standard tricks for iterations or products with countable supports of Sacks forcing. On the other hand it does not involve internal combinatorial structure of conditions of iterations or products. We prove that the class of forcing notions of type S is closed under products and certain iterations with countable supports.
INTERDEFINABILITY OF LAMBEKIAN FUNCTORS
Authors: Zielonka Wojciech , Zielonka W.
Published: May 2007

Several Gentzen‐style (sequential) syntactic type calculi with product(s) are considered. They form a hierarchy in such a way that one calculus results from another by imposing a new condition (expressed in terms of “structural rules”) upon the sequent‐forming operation. It turns out that, at some steps of this process, two different functors collapse to a single one. For the remaining stages of the hierarchy, analogues of Wajsbergs's theorem on non‐mutual‐definability are proved.
COMPACTNESS, THE LÖWENHEIM‐SKOLEM PROPERTY AND THE DIRECT PRODUCT OF LATTICES OF TRUTH VALUES
Authors: Ying Mingsheng , Ying Mingsheng
Published: May 2007

We show that compactness is preserved by arbitrary direct products of lattices of truth values and that the Löwenheim‐Skolem property is preserved by finite direct products of lattices of truth values.
ORDINAL NUMBERS IN ARITHMETIC PROGRESSION
Authors: Bagemihl Frederick , Bagemihl F.
Published: May 2007

The class of all ordinal numbers can be partitioned into two subclasses in such a way that neither subclass contains an arithmetic progression of order type ω, where an arithmetic progression of order type τ means an increasing sequence of ordinal numbers (ß + δγ)γ<γ<>r, δ ≠ 0.
TWO TOPOLOGICAL EQUIVALENTS OF THE AXIOM OF CHOICE
Authors: Schechter Eric , Schechter E.
Published: May 2007

We show that the Axiom of Choice is equivalent to each of the following statements: (i) A product of closures of subsets of topological spaces is equal to the closure of their product (in the product topology); (ii) A product of complete uniform spaces is complete.
EIN NEUER BEWEIS UND EINE VERSCHÄRFUNG FÜR DEN REDUKTIONSTYP ∀∃∀∞(0, 1) MIT EINER ANWENDUNG AUF DIE SPEKTRALE DARSTELLUNG VON PRÄDIKATEN
Authors: Deutsch Michael , Deutsch M.
Published: May 2007

A simultaneous semantical and syntactical reduction is given for the satisfiability respectively finite satisfiability of first order formulas. We choose ∀∃∀∞(0, 1) as conservative reduction class and allow only formulas out of ∀∃∀∞(0, 1) having a simple set theoretical model if they are satisfiable at all. With the same method we get a spectral representation of any ϱ‐ary enumerable respectively coenumerable predicate by a formula out of ∀∃∀∞(ϱ, 1).
ELIMINATION OF QUANTIFIERS OVER VECTORS IN SOME THEORIES OF VECTOR SPACES
Authors: Kuzichev Andrey A.
Published: May 2007

We consider two‐sorted theories of vector spaces and prove a criterion for the assertion that such a theory allows elimination of quantifiers over vector variables.
An Interpretation of the Zermelo‐Fraenkel Set Theory and the Kelley‐Morse Set Theory in a Positive Theory
Authors: Esser Olivier
Published: May 2007

An interesting positive theory is the GPK theory. The models of this theory include all hyperuniverses (see [5] for a definition of these ones). Here we add a form of the axiom of infinity and a new scheme to obtain GPK∞+. We show that in these conditions, we can interprete the Kelley‐Morse theory (KM) in GPK∞+ (Theorem 3.7). This needs a preliminary property which give an interpretation of the Zermelo‐Fraenkel set theory (ZF) in GPK∞+. We also see what happens in the original GPK theory. Before doing this, we first need to study the basic properties of the theory. This is done in the first two sections.
Non‐Complementedness and Non‐Distributivity of Kleene Degrees
Authors: Muraki Hisato
Published: May 2007

In this note, we study the complementedness and the distributivity of upper semilattices of Kleene degrees assuming V = L. K denotes the upper semilattice of all Kleene degrees. We prove that if V = L, then some sub upper semilattices of K are non‐complemented and some are non‐distributive.
On a Spector Ultrapower for the Solovay Model
Authors: Kanovei Vladimir , van Lambalgen Michiel
Published: May 2007

We prove that a Spector‐like ultrapower extension 𝔑 of a countable Solovay model 𝔐 (where all sets of reals are Lebesgue measurable) is equal to the set of all sets constructible from reals in a generic extension 𝔐[a], where a is a random real over 𝔐. The proof involves the Solovay almost everywhere uniformization technique.
Rudimentary Languages and Second‐Order Logic
Authors: More Malika , Olive Frédéric
Published: May 2007

The aim of this paper is to point out the equivalence between three notions respectively issued from recursion theory, computational complexity and finite model theory. One the one hand, the rudimentary languages are known to be characterized by the linear hierarchy. On the other hand, this complexity class can be proved to correspond to monadic second‐order logic with addition. Our viewpoint sheds some new light on the close connection between these domains: We bring together the two extremal notions by providing a direct logical characterization of rudimentary languages and a representation result of second‐order logic into these languages. We use natural arithmetical tools, and our proofs contain no ingredient from computational complexity.
Riesz basis and stabilization for the flexible structure of a symmetric tree‐shaped beam network
Authors: Wang Jun‐Min , Guo Bao‐Zhu
Published: May 2007

The stabilization of a symmetric tree‐shaped network of Euler–Bernoulli beams described by a system of partial differential equations is considered. The boundary controllers are designed based on passivity principle. The eigenfrequencies are analysed in detail and the asymptotic expansion of eigenvalues are presented. It is shown that there is a set of generalized eigenfunctions for the closed‐loop system, which forms a Riesz basis with parentheses for the energy state space. This concludes the spectrum‐determined growth condition and the exponential stability of the closed‐loop system. Copyright © 2007 John Wiley & Sons, Ltd.
The bioavailability of raspberry anthocyanins and ellagitannins in rats
Authors: Borges Gina , Roowi Suri , Rouanet Jean‐Max , Duthie Garry G. , Lean Michael E. J. , Crozier Alan
Published: May 2007

The fate of anthocyanins and ellagitannins in rats was monitored following ingestion of raspberry juice. After 1 h low nM concentrations of unmetabolised anthocyanins were present in plasma but these declined by 2 h and after 4 h they were no longer detectable. For the first 2 h there was an almost full recovery of anthocyanins as they passed from the stomach through the duodenum/jejunum and into the ileum. After 3 h less than 50% were recovered, and the levels declined rapidly thereafter. Excretion of raspberry anthocyanins in urine over a 24 h period was equivalent to 1.2% of the amount ingested. Trace quantities of anthocyanins were detected in the caecum, colon and faeces and they were absent in extracts of liver, kidneys and brain. Urine also contained a number of phenolic acids but most were present in quantities well in excess of the 918 nmol of anthocyanins present in the ingested juice. These findings indicate that raspberry anthocyanins per se are poorly absorbed, probably prior to reaching the ileum, and that substantial amounts pass from the small to the large intestine where they are degraded by colonic bacteria. Ellagitannins disappeared in the stomach without accumulation of ellagic acid.
The bioavailability and absorption of anthocyanins: Towards a better understanding
Authors: McGhie Tony K. , Walton Michaela C.
Published: May 2007

Evidence that anthocyanin compounds have beneficial effects for health are increasingly being reported in the scientific literature and these compounds are now widely recognised as potential therapeutic compounds. Berry fruit are rich sources of anthocyanins and berry fruit products or derived beverages can provide 10s to 100s of milligrams of anthocyanins in a single serve. Anthocyanins exhibit complex chemical behaviours in vitro and this will result in complex behaviour in vivo. This review attempts to summarize some aspects of anthocyanin biochemistry and discusses these in the context of what is currently known about bioavailability and absorption. Compared with other flavonoid groups, such as flavonols, relatively little is known about details and mechanisms of anthocyanin absorption and transport and much remains to be discovered.
Broadband flexible meander line antenna with vertical lines
Authors: Jung Jinwoo , Lee Hyeonjin , Lim Yeongseog
Published: May 2007

A novel broadband meander‐line antenna with vertical lines is presented. The proposed antenna has a broadband impedance bandwidth of ∼785 MHz, which covers DCS, PCS, UMTS, WiBro, and WLAN bands. For frequencies across the operating bands, the proposed antenna displays omni‐directional radiation patterns. The proposed antenna has compact dimensions of 12 × 23.1 mm2. The antenna is flexible due to the F‐PCB material used. For these reasons, a cylindrical and folded structure is presented, as transformed from planar. Experimental results using the constructed prototype are presented and discussed. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1984–1987, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22564
Randomness test of signal generated by microwave chaotic Colpitts oscillator
Authors: Shi Zhiguo , Zhang Ye , Liu Haiwen , Ran Lixin
Published: May 2007

Randomness test was conducted on signal sampled from the output of a microwave chaotic Colpitts oscillator operating with fundamental frequency of 960 MHz. Experimental data analysis shows the signal has an irregular distribution and a low degree of autocorrelation. Binary sequences converted from the signal can pass the four but one randomness tests in FIPS standard. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1981–1984, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22565
Efficiency ehancement of W‐CDMA base‐station envelope tracking power amplifiers via load modulation
Authors: Jeong Jinho , Asbeck Peter
Published: May 2007

Load impedance modulation and gate bias control were investigated to improve the performance of W‐CDMA base‐station envelope tracking amplifiers by means of simulations based on the measured data of a 10‐W GaAs FET power amplifier. It is shown that adapting the load impedance along with the drain bias voltage can effectively improve the average efficiency of envelope tracking amplifier. The improvement becomes more apparent in the operating regime of power back‐off. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1954–1957, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22566
Bidirectional artificial magnetic reflectors at microwave frequencies
Authors: Ferrer P. J. , González‐Arbesú J. M. , Romeu J. , Cardama A.
Published: May 2007

Metamaterial slabs made of magnetic resonators (artificial magnetic conductor, AMC surfaces) can provide unusual electromagnetic properties, such as the dual PMC/PEC behavior, when used as reflectors. This property has been assessed and tested with the design and fabrication of a one‐layer spiral AMC slab. Moreover, two bidirectional AMC surfaces have also been designed and measured. These structures, composed of spiral (SR) or capacitive loaded loop (CLL) resonators printed on dielectric strips, can provide 0° reflection coefficient phase when the incident electric field wave impinges on any side. A very low electrical thickness is achieved. Compact antenna systems with two (or more) close isolated antennas can be designed with such structures. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1949–1953, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22567
A band‐pass filter consisting of two substrate integrated waveguide cavities coupled by an aperture on their common side wall
Authors: Hwang R. B. , Chang C. W.
Published: May 2007

In this article, we present a substrate‐integrated waveguide‐based band‐pass filter with wide stop‐band rejection property. This band‐pass filter is made up of two substrate‐integrated waveguide cavities, which couple to each other by an aperture on their common waveguide side wall. By using the empirical formula [19] for obtaining the equivalent rectangular waveguide dimensions, the substrate integrated waveguide structure could then be properly approximated by a closed rectangular waveguide. We employed the rigorous mode‐matching method to analyze the electromagnetic boundary‐value problem of the structure containing multiple discontinuities. In comparison with the conventional end‐to‐end coupled cavity filters, we found that our new side‐wall‐coupled cavity filter can suppress the second resonance frequency and therefore, provide a considerably wide rejection band. It is interesting to note that the suppression of the second resonance frequency can be achieved by properly shifting the second cavity in lateral direction. To explore its physical insight, the resonant modes in the substrate integrated waveguide cavities are carefully inspected for realizing the physical picture of wave process taking place in the two cavities system. In addition to the theoretical analysis, we have fabricated the filters and measured their scattering parameters. The good agreement between the theoretical and measured results validates the accuracy of numerical computation, and also shows the promising performance of the proposed filters. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1884–1887, 2007; Published online in Wiley Inter‐Science (www.interscience.wiley.com). DOI 10.1002/mop.22570
Characteristics of compact‐size D lens collimator for micro‐optics devices applications
Authors: Lin Yu‐Cheng
Published: May 2007

A compact‐size D lens collimator was fabricated and characterized. High circular rate 98%, small divergence angle 0.186°, and low return loss 59.8 dB were achieved in experiment to present the excellent performance of D lens collimator. Insertion loss sensitivity due to variation in working distance, operating wavelength, and misalignment tolerance were demonstrated in experiment and verified with theoretical simulation by OSLO. It is worth to note that the compact‐size D lens collimator exhibits low insertion loss, less than 0.3 dB, not only for large working distance range 10–30 mm but also for wide operating wavelength band 1560 ± 50 nm. When compared with gradient index lens collimators, the D lens collimator is potentially suitable for the application in the design of micro‐optics devices. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1946–1949, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22581
Multiband meander antenna with a backed microstrip line
Authors: Kim Jae H. , Lee Jung N. , Kim Hyun H. , Lee Jae C. , Park Jong K. , Kim Hak S.
Published: May 2007

A novel multiband meander antenna with a backed microstrip line is proposed for GSM/DCS/ISM and WiMAX triple‐band operations. We have used meandering technique and U‐shaped line to produce the GSM and DCS bands, respectively, and a backed microstrip line technique to produce the ISM and WiMAX band. Prototypes of the multiband antennas have been successfully implemented and good radiation characteristics in the operating frequency bands have been achieved. The effect of the backed microstrip line geometry on the return loss was also studied. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1942–1946, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22582
Increasing the efficiency of microstrip interconnects using additional coupling capacitors
Authors: Khalaj‐Amirhosseini M. , Moeeni‐Fard M.
Published: May 2007

A way to increase the efficiency of previously designed microstrip interconnects is adding discrete capacitors between their strips. A closed form relation is obtained for optimum value of additional capacitors for previously designed microstrip interconnects, in this article. The effect of adding discrete capacitors is verified using an experimental example. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2035–2037, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22591
A wideband microstrip bandpass filter for ultra‐wideband wireless communication application
Authors: Gao Shanshan , Xiao Shaoqiu , Wang Jianpeng , Yang Xuesong , Wang Bing‐Zhong
Published: May 2007

A novel wideband bandpass filter for ultra‐wideband system application is proposed, designed, and implemented on the basis of a modified stepped impedance resonator structure. The modified stepped impedance resonator can not only generate multiple‐resonant peaks within the ultra‐wideband passband but also easily realize a tight coupling with the feed‐lines. Both simulation and measurement results are presented and they are in good agreement. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1975–1976, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22594
Spiral antenna with helix loaded for dual circularly polarized bands radiation
Authors: Chen Can‐Hui , Yung E. K. N. , Hu Bin‐Jie
Published: May 2007

A spiral antenna with a helix loaded is investigated in this paper. Through combining the spiral with a helix together, circular polarization can be achieved in dual bands. Since the helix is loaded in the lower part of the spiral, this technique doesn't increase the antenna's volume but at the same time introduces another CP band. The experimental result shows that the lower band and upper band are 4.0% and 62.07% respectively. The characteristics of impedance, current distribution and radiation pattern will also be presented. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1939–1942, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22596
A new compact balance‐fed T‐monopole antenna for UMTS mobile applications
Authors: Chiu Cheng‐Nan , Chen Hung‐Ruei
Published: May 2007

A balance‐fed T‐monopole printed antenna is newly proposed in this letter for modern mobile applications. This T‐monopole antenna is for stripline‐feeding with balanced signals. The antenna is compact and has the particular merit of immunity to the influence of size variation in feed ground. A prototype of the antenna for operating at the universal mobile telecommunication system (UMTS) band has been constructed and is shown as an example. Its return loss and radiation patterns have been simulated and measured. The experimental results demonstrate the broad bandwidth and omnidirectional radiation characteristics of the newly developed antenna, as well as the merits summarized here. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1904–1907, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22598
Internal multiband printed folded slot antenna for mobile phone application
Authors: Wong Kin‐Lu , Chi Yun‐Wen , Tu Shu‐Yang
Published: May 2007

A novel printed folded slot antenna suitable for GSM/DCS/PCS/UMTS multiband operation in the mobile phone is presented. The proposed slot antenna has a planar configuration and is easy to fabricate by printing on the system circuit board of the mobile phone. The slot antenna has a length of 106 mm and is folded into a compact structure with its two slot ends facing toward each other. This configuration allows the antenna to occupy a small area of 21 × 45 mm2 centered on the top portion of the system ground plane. By feeding the slot antenna using a 50 Ω microstrip line printed along the centerline of the system ground plane, two wide bands (the half‐ and one‐wavelength modes) of the antenna can be generated, with the lower band covering GSM operation and the upper band covering DSC/PCS/UMTS operation. In addition, small excited surface currents in the system ground plane are observed, and the antenna's two operating bands are in general not sensitive to the ground‐plane length variations. These features are attractive for practical applications and different from those of the conventional internal mobile phone antennas. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1833–1837, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22602
Dielectric wedge antenna with stepped phase correction in a nonradiative mode
Authors: Malherbe J. A. G. , Malekela P. M.
Published: May 2007

The performance of a dielectric wedge antenna with stepped phase correction in a nonradiative dielectric structure is described. The stepped wave numbers are achieved by perforating the dielectric with a series of holes designed to modify the dielectric constant in a predetermined fashion. The aperture of the wedge is then divided into a number of zones, each with its own dielectric constant. The step correction of the aperture phase error results in a substantial improvement in radiation pattern. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2030–2032, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22607
Application of the FDTD method to determine complex permittivity of dielectric materials at microwave frequencies using a rectangular waveguide
Authors: Terhzaz Jaouad , Ammor Hassan , Assir Abdelhadi , Mamouni Ahmed
Published: May 2007

A new measurement technique is presented to determine the complex permittivity of a dielectric material. The dielectric sample is loaded in a short‐circuited rectangular waveguide. The reflection coefficient of the waveguide is measured by Network analyzer and calculated as a function of the complex permittivity using finite difference time domain method (FDTD). The Newton–Raphson method is then used to determine complex permittivity by matching the calculated value with the measured value. A comparison of determined values of the dielectric constant obtained from the Nicholson–Ross technique and the FDTD method is presented. Numerical resultants for complex permittivity of Teflon and Plexiglass measured at the microwave frequencies are presented. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1964–1968, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22611
Radiation characteristics of a monopole‐type antenna and an inverted‐F antenna for mobile handset applications
Authors: Kim Jeong I. , Yoon Dongweon , Cho Kyongkuk
Published: May 2007

Two types of wire antennas, a monopole‐type antenna (MTA) and an inverted‐F antenna (IFA), to be internally mounted in a mobile handset, differing only in the presence of a shorting point for the IFA, are proposed, analyzed numerically and experimentally, and compared. Agreement is remarkable between the numerical and experimental analyses for the electromagnetic radiation patterns. Radiation pattern characteristics of the MTA are close to those of the IFA over the frequency range from 3.0 to 3.6 GHz. On the other hand, the resonance frequency and bandwidth are changed by a fraction of 10 and 3%, respectively. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1931–1935, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22612
Unconditionally stable Laguerre‐based BOR‐FDTD scheme for scattering from bodies of revolution
Authors: Chen Hai‐Lin , Chen Bin , Duan Yan‐Tao , Yi Yun , Fang Da‐Gang
Published: May 2007

This work presents a new unconditionally stable BOR‐FDTD method based on weighted Laguerre polynomials. To validate the accuracy and efficiency of the proposed method, we apply it to analyze the scattering from a PEC cylinder with a slot. Comparing the results from the proposed method and those from the conventional BOR‐FDTD method, they show good agreement. And a substantial savings in computational time is achieved. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1897–1900, 2007; Published online in Wiley Inter‐Science (www.interscience.wiley.com). DOI 10.1002/mop.22614
Harmonic‐suppressed slot‐coupled microstrip patch antenna with enhanced bandwidth
Authors: Ooi S. F. , Lee S. K. , Sambell A. , Korolkiewicz E. , Gao S. , Butterworth P.
Published: May 2007

This letter presents a slot‐coupled microstrip patch antenna with harmonics suppression capability within an enhanced bandwidth. Measured return loss result at the operating frequency, second harmonic frequency, and third harmonic frequency were 22.2 dB, 1.77 dB, and 1.93 dB, respectively, with a 9% impedance bandwidth around 2.45 GHz. The antenna is a good candidate for further integration with class‐F amplifiers. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1827–1829, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22618
Fabrication and measurement of triangular‐slot antenna for triple‐band (2.4/5.2/5.8 GHz) antenna with rectangular tuning stub
Authors: Yoon JoongHan , Jeong Gyey Teak , Kwak Kyung Sup
Published: May 2007

In this paper, a novel design of a triangular‐slot antenna with rectangular tuning stub for 2.4/5.2/5.8 GHz triple‐band applications is presented. The prototype consists of a triangular slot and rectangular tuning stub. Results show that the impedance matching of the proposed antenna is greatly affected by the feed gap width. Experimental results indicate that the impedance bandwidth (VSWR 1:2) of the proposed antenna is about 423 MHz for the 2.4‐GHz band and 1.92 GHz for the 5‐GHz band. The simulated and experimental results for the return loss, radiation patterns, and gains are presented and discussed. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1793–1797, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22621
Design and performance of ultra low phase noise reflection whispering gallery resonator oscillator
Authors: Shtin Nicolás A. , Romero J. M. López , Prokhorov Eugen
Published: May 2007

This article deals with the design and experimental testing of the ultra low phase noise reflection oscillator incorporating a sapphire whispering gallery resonator (WGR). On a contrast with the conventional loop configuration oscillators with transmission WGR the presented oscillator is based on a reflection WGR excited by a single probe. It is shown that a phase noise of C‐band oscillator of the proposed configuration can be as low as −136 dBc/Hz at 1‐kHz Fourier frequency. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2026–2030, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22623
Design of wideband high and low impedance metatransmission lines
Authors: Perruisseau‐Carrier J. , Skrivervik A. K.
Published: May 2007

The modeling and design of “metamaterial ” composite right/left handed transmission lines (CRLH‐TL) is usually based on the assumption that its unit cell is small in terms of the host TL wavelength (d ≪≪λ0). However, it was also shown that this assumption is not required for most CRLH‐TL applications and difficult to meet for balanced CRLH‐TLs in particular cases. Thus, a more general design strategy, free of this assumption, has been implemented. In this letter, we further develop this second approach to show that it allows designing CRLH‐TLs whose impedance is much beyond the range achievable in the case where d ≪λ0, for a given technology and fabrication tolerances. The use of the presented concept is illustrated by means of a quartz‐integrated CRLH‐TL exhibiting a low‐impedance (20 Ω). Measured results are in good agreement with the theory and satisfactory performances are observed on a bandwidth covering almost the entire Ku band. Potential applications of the presented results are also discussed in a dedicated section. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1926–1929, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22628
Switchless bidirectional amplifier for wireless communication systems
Authors: Bechteler A. Sevinc Aydinlik , Bechteler Thomas F.
Published: May 2007

A bidirectional amplifier working at 2.4 GHz is presented in this article. The presented amplifier is able to amplify two signals simultaneously. This, since commonly used radio frequency switches are replaced by circulators. The amplifier is designed on a single small‐sized printed circuit board. First, the new amplifier circuit is proposed and characterized. Then, its advantages and design problems are analyzed. Finally, design instructions are setup in order to obtain a good performance of the switchless amplifier within the frequency band of interest. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1888–1890, 2007; Published online in Wiley Inter‐Science (www.interscience.wiley.com). DOI 10.1002/mop.22631
Using WCS‐FDTD method to simulate various small aperture‐coupled metallic enclosures
Authors: Chen Juan , Wang Jianguo
Published: May 2007

The weakly conditionally stable finite‐difference time‐domain (WCS‐FDTD) method is employed to compute the electromagnetic coupling and shielding of various small aperture‐coupled metallic enclosures. In the WCS‐FDTD method, a larger time‐step size than allowed by the CFL stability condition limitation can be set because the algorithm of this method is weakly conditionally stable. Consequently, an increase in computational efforts caused by fine cells due to small apertures can be prevented. The results from the WCS‐FDTD method agree well with results from the conventional finite‐difference time‐domain (FDTD) method, and the required CPU time for the WCS‐FDTD method is much shorter than that for the FDTD method. Compared with the ADI‐FDTD method, the WCS‐FDTD method has better accuracy and higher efficiency, which is demonstrated by numerical examples. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1852–1858, 2007; Published online in Wiley Inter‐Science (www.interscience.wiley.com). DOI 10.1002/mop.22633
The numerical study of pulse evolution in self‐similar parabolic pulse amplifier
Authors: Chenghou Tu , Fuyun Lu , Ting Lei , Yongnan Li , Wengang Guo , Xiaoyi Dong
Published: May 2007

In this article, the influences of initial pulse and gain fiber parameters on the pulse's self‐similar evolution are studied by numerical simulation. We propose and demonstrate that dispersion length is the determining factor of pulse's self‐similar evolution. For a given input pulse, if dispersion length is comparable or smaller than fiber length, it can evolve into similariton, otherwise it can not. Under the self‐similar evolution condition, increasing pulse energy and gain coefficient can accelerate self‐similar evolution, otherwise the effect is not evident. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1785–1787, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22636
Theoretical and practical experiments for a single antenna gain testing method: Application to wireless communication devices
Authors: Anguera Jaume , Sanz Alfonso , Ko Young‐Jik , Borja Carmen , Puente Carles , Soler Jordi
Published: May 2007

A compact antenna gain measurement system suitable for wireless devices is presented. The method needs the antenna under test, a planar electric conductor, and a vector analyzer. It is possible to obtain the total gain by a reflection measurement. Several simulations show a guideline to optimize the set‐up. Finally, some wireless devices operating at GSM900, GSM1900, and Bluetooth® are tested and compared with gain obtained by a three radiation pattern method. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1781–1785, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22637
Differential form approach to the analysis of electromagnetic cloaking and masking
Authors: Teixeira F. L.
Published: May 2007

We discuss the relationship between (a) electromagnetic masking or cloaking of objects produced by some metamaterial blueprints and (b) some invariances of Maxwell equations obviated by means of differential forms (exterior calculus). © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2051–2053, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22640
A microstrip bandgap filter with the photonic band gap resonators
Authors: Wang S. , Guo M. S. , Sun C. L. , Yang H. L. , Zhao X. Z.
Published: May 2007

A microstrip bandstop filter using four square air holes resonator at frequencies above 10 GHz has been investigated. The square air holes resonator generate a bandgap, and its operation mechanism is made clearly through the Finite Differential Time‐Domain method. The measured frequency response of the filter is in good agreement with the simulation, and the center frequency of stopband of the microstrip filter shifted to higher frequency along with the dimension of the square air holes increased. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2020–2022, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22641