bluuebunny/crossref_metadata_2025_split huggingface dataset:
A CMOS power amplifier with an adaptive bias scheme for mobile radio frequency identification reader applications
Authors: Han Jeonghu , Kim Younsuk , Park Changkun , Lee Dongho , Hong Songcheol 
Published: March 2007

AbstractA 900‐MHz linear power amplifier with an adaptive bias scheme is fabricated using a 0.25‐μm CMOS technology. The power amplifier operates over the range of 860–960 MHz, which is the ultrahigh‐frequency band for radio frequency identification (RFID). All matching networks and RF chokes are implemented on a chip. The developed power amplifier provides a 1‐dB‐gain‐compression point (P1 dB) of 27 dBm and a power‐added‐efficiency (PAE) of 28% at theP1 dB. The adaptive bias scheme enables the power amplifier to reduce the quiescent power consumption from 280 to 80 mW by adjusting the gate voltage of power transistors as a function of the input power. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1241–1245, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22435
Optical single sideband modulation based on Sagnac interferometer employing in true time delay
Authors: Liu Zhigang , Zheng Xiaoping , Zhang Hanyi , Guo Yili , Zhou Bingkun 
Published: March 2007

AbstractPolarization maintaining fiber in a Sagnac interferometer is used to generate optical single sideband (OSSB) that can overcome the power penalty brought by optical double sideband modulation in fiber links. This OSSB modulation used in true time delay (TTD) can form digital TTD and overcome the power penalty. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1492–1494, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22436
A band‐pass filter using via‐hole‐wall cavity
Authors: Hwang Ruey Bing , Pan Jun Liang 
Published: March 2007

AbstractIn this paper, we presented a band‐pass filter consisting of a post‐wall cavity resonator. This band‐pass filter was fabricated in a two‐layered printed circuit board, which includes an input and an output substrate integrated waveguides as the feeding structures in the top layer and a cavity in the bottom layer. The interconnection of the signal between different layers is achieved via the apertures etched on the input and output waveguides and cavity. We found the bandwidth of such a class of band‐pass filter could be altered by tuning the length of the coupling apertures. Besides, the pass‐band frequency can be estimated by the resonant frequencies of the cavity. We have fabricated the band‐pass filter on a low‐loss dielectric substrate and measured its S‐parameters, including the return‐ and insertion‐ loss. In addition, the numerical simulation by the CST microwave studio, a full‐wave time‐domain numerical method, was also carried out. A good agreement between the measured and simulation results was obtained. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1456–1459, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22438
Stable narrow linewidth Er‐doped fiber laser at 1550 nm
Authors: Wu Bo , Liu Yongzhi , Dai Zhiyong , Liu Shuang 
Published: March 2007

AbstractA narrow linewidth fiber laser based on fiber Bragg grating Fabry‐Perot etalon is demonstrated. Spatial hole burning effect is restrained by fiber Faraday rotator. The short fiber Bragg grating Fabry‐Perot etalon as narrow bandwidth filter discriminates and selects laser longitudinal modes efficiently. Stable single frequency 1550 nm laser is acquired. Pumped by 976 nm laser diode, the fiber laser exhibits 11 mW threshold. Output power (50 mW) is obtained upon the 200 mW pump power. Optical‐optical efficiency is 25% and slope efficiency is 27%. The linewidth of laser is less than 10 kHz, measured by the delayed self‐heterodyne method with 10 km single mode fiber. In addition, the lasing linewidth keeps less than 10 kHz over 1 nm tuning range in the temperature tuning experiment. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1453–1456, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22439
THz characterization of high dielectric‐constant materials using double‐layer sample
Authors: Kapilevih B. , Litvak B. 
Published: March 2007

AbstractA method of measurement of the real and imaginary parts of high dielectric constant materials at THz frequencies is described. The method is based on application of double‐layer sample with variable distance between slabs. The recorded power transmittance inerferogram is employed for reconstructing complex permittivity of a material under test. Reconstructing algorithm and its realization are presented. Example of measurements of the alumina sample in 0.8–1.1 THz has demonstrated a good agreement with independent data obtained from the time‐domain terahertz spectroscopy method. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1388–1391, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22442
Gain equalization methods in erbium‐doped fiber amplifiers
Authors: de Benito Paula , Diaz Silvia , Abad Silvia , Lopez‐Amo Manuel 
Published: March 2007

AbstractWe show experimental performance comparison of different equalization methods in erbium‐doped optical amplifiers based on silica and ZBLAN host materials. Different configurations are analyzed, including the analysis of hybrid silica/ZBLAN configurations, exploring gain, bandwidth, and noise figure performance. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1346–1349, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22445
Novel compact 2.4/5‐GHz dual‐band T‐slot antenna for WLAN operations
Authors: Ren Wang , Shi Zhiguo , Liu Haiwen , Chen Kangsheng 
Published: March 2007

AbstractThis paper proposes a novel compact dual‐band T‐slot antenna for 2.4/5‐GHz wireless applications. The proposed antenna is composed of two orthogonal slots in a 20 mm by 50 mm ground plane. The antenna was fabricated on a FR‐4 substrate (εr = 4.50, tan δ = 0.02) and was measured in a microwave anechoic chamber. The experimental data and the simulation results agree well with each other and show that the proposed antenna can completely cover both 2.4/5‐GHz bands with satisfactory radiation characteristics. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1236–1238, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22451
Double‐layer substrate integrated waveguide structure with variable fractional bandwidth
Authors: Xu Lei , Che Wenquan , Geng Liang , Wang Dapeng 
Published: March 2007

AbstractThe propagation characteristics of double‐layer SIW structures have been investigated in this paper. On the basis of the theory of resonance cavity and SIW, the simple theoretical formulas for the lower and upper frequencies in the passband have been found. The theoretical analyses have indicated that these two frequencies have much dependence on the width of SIW and the length of the coupling slot, the fractional bandwidth of the double‐layer SIW structures can be controllable. Agreement between the simulation data and the calculated results from the formulas can be observed. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1459–1463, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22469
Preparation and fluorescent properties of poly(vinyl alcohol) bearing coumarin
Authors: Wang Baoyan , Guan Xiaolin , Hu Yulin , Su Zhixing 
Published: April 2007

AbstractA novel water‐soluble fluorescent material was prepared via ring‐opening reaction between 4‐methyl‐7‐(2,3‐expoxypropoxy) coumarin (MEC) and poly(vinyl alcohol) (PVA). The fluorescent behaviors of this material (PVA–MEC) in solution, solid and film were studied in detail. The results showed that the fluorescence of PVA–MEC arose from isolated dye molecules and had a good film forming ability. In addition, the effects of acid/base environments on PVA–MEC were studied and the results showed that it was less affected by environment than 7‐HMC. Moreover, relative fluorescence intensity of PVA–MEC had an excellent linear response in the temperature range of 0–60°C. These observations suggest that PVA–MEC is an excellent fluorescent macromolecular material with a convenient method of preparation and had a good water‐soluble ability. Copyright © 2007 John Wiley & Sons, Ltd.
Alumino‐silicate polyacrylic acid and related cements
Authors: Wilson A. D. 
Published: March 2007

AbstractThe composition and setting reaction of cements formed from aluminosilicates and poly(acrylic acid), the ASPA cements, are described. Setting and hardening results from interactions between specially‐formulated, complex, fluorine‐containing calcium aluminosilicate glasses and aqueous solution of poly(acrylic acid) or similar poly(alkenyl carboxylic acids). Protons from the polyacid penetrate the surface of the glass decomposing the negatively charged aluminosilicate network to a siliceous hydrogel and releasing Al3+, Ca2+ and F‐ ions. These ions migrate, probably as complexes, such as AlF2+, AlF2+ and CaF+, into the polyelectrolyte phase where they cross‐link polyanionic chains, by ionic and possibly chelate binding, causing the cement to gel and set. Overall the reaction may be seen as one where flexible hydrogen bonds, in the liquid, are progressively replaced by more rigid ionic ones, leading to gelation.The set cement is a composite of glass particles sheathed by a silica gel bound by a metal poly anionic matrix. ASPA cements can attain a compressive strength of 200 N/mm2 in 24 h and are adhesive under oral conditions to tooth materials. They find a number of applications in conservative and preventive dentistry.Certain naturally‐occurring aluminosilicate minerals react with poly(acrylic acid) to form cement but these are much weaker (not exceeding a compressive strength of 30 N/mm2) and are weakened by water.
Production of organometallic polymers via the interfacial technique. reaction variables in the condensation of diamidoximes with cp2ticl2 and partial thermal characterization of the products
Authors: Carraher Charles E. , Frary Ronald 
Published: March 2007

AbstractReaction variables of the interfacial condensation of Cp2TiCl2 with diamidoximes is presented. At 1:1 Cp2TiCl2: diamidoxime ratios and less the product is found to contain predominately units of form I. It is tentatively concluded that the disubstituted product, form II, is formed at Cp2TiCl2:diamidoxime ratios > 1. Sodium hydroxide and triethylamine are both found to be adequate added bases for the reaction.magnified imageHigh concentrations of Cp2TiCl2 and low concentrations of diamidoxime favour a more rapid reaction.Thermal degradation of the products in air and nitrogen occur via identical pathways.
Fundamental properties of densified polymeric glasses
Authors: Wetton Raymond E. , Moneypenny Harry G. 
Published: March 2007

AbstractGlass forming high polymers have been densified by application of high hydrostatic pressure (∼1.5 kbar) in the melt followed by cooling under pressure to ambient. A density increase of about 1% was induced in each of the following polymers: polyvinylchloride, polymethylmethacrylate, polystyrene, poly‐4‐chlorostyrene, poly‐3‐chlorostyrene, poly‐4‐methoxystyrene and poly‐4‐phenoxystyrene. Differential thermal analysis (DSC) and volume relaxation techniques were used to study the reversion of the densified glass to a more normal glass at a temperature ∼Tg – 15 K in general. Enthalpy relaxation (a change from glass I to glass II) in this region gives a peak or diffuse hump on the DSC scan prior to a normal glass transition temperature. It is considered that although the densified glasses may become thermodynamically stable at a sufficiently low temperature they are inherently unstable at ambient. Reversion to a more normal glass is kinetically too slow to measure at ambient in all cases studied except polymethylmethacrylate. Changes of dynamic Young's moduli and dielectric constant with densification are reported in detail for some systems and in summary for others. The densified glasses exhibit moduli higher by ∼6%, dielectric constant higher by ∼2% and depressed secondary mechanical and dielectric relaxation processes. Ultimate property studies are reported for PVC.
Preparation and characterisation of styrene—methyl methacrylate and styrene–methacrylic acid copolymer latices
Authors: Ono Hiroshi , Jidai Eiki , Shibayama Kyōichi 
Published: March 2007

AbstractSeries of styrene‐methyl methacrylate and styrene‐methacrylic acid copolymer latices have been prepared by emulsion polymerisation using polyoxyethylene nonyl phenyl ether as emulsifier and potassium persulphate as initiator. the effects of surfactant concentration and monomer composition on the ultimate particle size and conversion were investigated. The ultimate particle diameters decreased with increasing surfactant concentration, while the conversions were found to be almost independent of surfactant concentration. The ultimate particle diameters were notably decreased by increasing the content of methacrylic acid. Trace carboxyl groups were detected both in polystyrene latex and styrene‐methyl methacrylate copolymer latices. The number of sulphate groups on the polystyrene latex surface was about five times that of carboxyl groups.
Infrared spectra of chlorinated petroleum fractions
Authors: Sosa José M. 
Published: March 2007

AbstractThe infrared spectra of several chlorinated petroleum fractions are reported. Although the spectra of chlorinated branched and linear fractions are different in the 600–800 cm−1 region, it is very difficult to detect less than 15% of the toxic chlorinated kerosene in mixtures with chlorinated n‐paraffin waxes.
Tg/Tm for unsubstituted polymers
Authors: Boyer Raymond F. 
Published: April 2007

AbstractPolymers under discussion can be represented by [CH2)nR]p where R is CH2, CF2, O, S or CH = CH; and where n can vary from 0 to ∞. The copolymer, P(ethylene‐alt‐TFE) is also included. These polymers tend to be highly crystalline with resultant confusion about their Tg and hence their Tg/Tm values and a clarification scheme is proposed in which it is considered that each such polymer has a double glass transition, Tg(L)/f(χc), Tg(U) = F(χc); and a sub‐glass T<Tg(L) at 0.75 Tg(L), where F(χc) signifies a function of fractional crystallinity, χc. T<Tg(L) and Tg(L) increase linearly with Tm. The ratio, Tg(L)/Tm, is therefore, not a constant but is close to 0.5. T<Tg(L)/Tg(L) is also not a constant but is close to 0.75. Tg(U) lies within a wedge whose top and bottom sides increase with Tm. The premelting, intracrystalline transition temperature, Tαc, is also a linear function of Tm. It is suggested that the scheme outlined above should help to resolve uncertainties in assigning transition temperatures for unsubstituted polymers. The low Tg/Tm values for these polymers is discussed in terms of their small da/dc ratios and small crosssectional areas per chain.
Heat‐resistant resins obtained by polycondensation of aromatic aldehydes with methylpyridines
Authors: Bloch B. , Ropars M. 
Published: April 2007

AbstractPolycondensation of terephthalic aldehyde with 2,4 — or 2,6‐dimethyl ‐, or 2,4,6 — trimethylpyridine leads to a new kind of heat‐resistant resin with aromatic‐heterocyclic structure.These resins are mixtures of thermosetting oligomers. A few components have been identified after separation by size‐exclusion chromatography. Although infrared spectroscopy sheds some light on certain aspects of their heat‐curing mechanism, this has not yet been fully elucidated.Derivatives of trimethylpyridine (symmetrical collidine) appear to be particularly interesting in view of their possible use with reinforcing fibre materials for prepreg fabrication. These derivatives lead to composite materials whose high mechanical properties remain unaffected for several thousand hours at 250°C and a few hours at 350°C.These products are being developed on an industrial scale under the name of PSP resins.
Effect of substituents in the styrene aromatic ring on water absorption and thermal stability of an unsaturated polyester resin
Authors: Douglas William E. , Pritchard Geoffrey 
Published: April 2007

AbstractThe water absorption at 50°C and dynamic and isothermal thermogravimetric properties were studied for a series of resins made from the same maleic/phthalic anhydride‐based unsaturated polyester cross‐linked with each of styrene, 4‐methyl styrene, 4‐ethyl styrene, 4‐n‐butyl styrene, 4‐isopropyl styrene, tertiary butyl styrene, 4‐chlorostyrene and 3,4‐dichlorostyrene. Chloro substituents and most alkyl groups give rise to a loss of water resistence. However, the tertiary butyl group leads to a decrease in both water absorption and water damage. The thermal stability of the resin is decreased by chloro substituents and increased by n‐alkyl groups, and the results suggest that the main degradation step involves styrene residues, but that the initial decomposition does not do so.
Curing characteristics of anaerobic sealants and adhesives
Authors: Stamper David J. 
Published: April 2007

AbstractDuring the past 20 years the usage of anaerobic‐curing sealants and adhesives has grown rapidly from almost nothing to an estimated 1500 tonnes per annum. An annual growth rate in excess of 10% is predicted throughout the present decade.In this paper, the gradual improvement in the performance characteristics of these systems is traced, from the somewhat uncommercial earliest formulations which required air or oxygen to be bubbled continuously through the system in order to prevent premature gelation, to the present day systems which cure rapidly on most metallic substrates yet possess shelf lives in excess of twelve months.Reaction mechanisms are postulated for the ever‐more efficient curing systems being developed and also for the extremely delicate balance between high reactivity and extended storage stability in commercially available products.
Positron annihilation measurements and their application to thermosets
Authors: Coleman Clifford F. , Smith Frederick A. , Hughes Anthony E. 
Published: April 2007

AbstractPositrons which annihilate with electrons in solids usually give rise to two gamma rays, each with an energy close to 0.511 MeV, which are emitted in almost exactly opposite directions. The spread of the energies about the nominal value, which amounts to a few keV, is a Doppler effect reflecting the velocities along the direction of gamma emission of the electrons with which the positrons happen to annihilate. Thus the shape of the annihilation line gives a weighted measure of the electron momentum distrubution, emphasising the conduction electrons and the loosely bound localised electrons. The Positron Annihilation Techniques (PAT) allow this distribution to be determined non‐destructively, and lend themselves to comparative measurements. If some of the positrons are trapped at negatively charged sites within a solid the annihilation radiation will reflect both the changed momentum distribution of the electrons seen at the trapping sites and the relative number of positrons which are trapped at the time of annihilation. To be effective the traps must have a mean spacing < 100 nm, but the sensitivity of PAT to atomic scale traps such as vacancies can nevertheless be very high. Finally, in materials containing few free electrons, information can be extracted from the formation of the positron analogue of the hydrogen atom, positronium.With standard positron sources probing depths in plastics can be a few millimetres. The PAT techniques have already proved their worth in investigations of electron momentum distributions in ordered solids, and in investigations of phase changes and of mechanical and fatigue damage in metals and alloys. Their out‐of‐the‐way combination of characteristics makes them well worth consideration in other materials applications when conventional techniques run into difficulties.
The application of ultra‐violet microscopy to thermosetting polymers
Authors: Billingham Norman C. , Calvert Paul D. , Ghaemy Mosa G. 
Published: April 2007

AbstractOptical microscopy with ultra‐violet illumination has been used to monitor the curing reactions and final structure of an amine‐cured epoxy resin system. When low concentrations of u.v. absorbing additive are added to the resin before curing, the additive is usually completely uniformly distributed in the cured product. No density variations on a scale resolvable in optical microscopy are visible. Similarly when a u.v. absorbing eragent is allowed to diffuse into the cured resin its diffusion profile is normal and shows no detectable density fluctuations in the resin. Reaction of cured resins with a reagent which couples with amino groups to give u.v. absorbing adducts shows that conventional hand mixing techniques do not produce complete mixing of the resin components and spatially non‐uniform concentrations of unreacted amines are found. This effect can only be removed by unusually thorough mixing techniques. Use of a water soluble u.v. absorber allows penetration of the epoxy by water to be followed. In particular, the penetration of fibre‐matrix interfaces by water can be visualised.
Rubber‐Toughened Polyester Resins
Authors: Alexander I. J. 
Published: April 2007

AbstractBlending elastomers into plastics to produce polymer composites with improved properties, particularly toughness, is a well known technique exemplified by such products as high‐impact polystyrene (HIPS), ABS and rubber‐toughened epoxies. In this present work a wide range of elastomers has been studied to find polyester resin‐rubber compositions which are storage‐stable, have acceptable rheology and cure characteristics, and, when cured, provide materials with significantly improved toughness.It has now been shown that commercially available liquid rubbers, when suitably modified, will remain dissolved in the resin without separation, and that the cured polyester‐rubber composition has a complex polyphase morphology which resembles, for example, that found in HIPS. The fracture energy of these materials has been shown to be many times that of conventional polyester resins.In further work methods have been developed which make possible the incorporation of much higher molecular weight rubbers into polyester resins to produce impact resistant products.
Some aspects of the effects of fillers on the behaviour of PVC in fires
Authors: Matthews George , Plemper George S. 
Published: April 2007

AbstractThe effects of particle size and concentration of calcium carbonate fillers on the critical oxygen index and the evolution of hydrogen chloride during pyrolysis of unplasticised PVC has been shown to parallel the effects in plasticised PVC but to differ from them in two respects. Coarser varieties of calcium carbonate (i.e. appreciably greater than 0.1 micron) react with pyrolysis hydrogen chloride more efficiently in UPVC than in plasticised PVC.Plots of critical oxygen index against concentration of calcium carbonate in UPVC show two inflexions, maxima at low concentrations (i.e. < 30 PHR) and minima at high concentration (i.e. > 40 PHR). Similar inflexions are also shown with alumina trihydrate and silica. In both plasticised and unplasticised PVC, calcium oxide produces a steady fall in critical oxygen index with increasing concentration, more marked than with calcium carbonate at equal hydrogen chloride retentions.The complex behaviour is attributed to the number of factors contributing to overall burning behaviour. Of these, char formation, in particular, is not readily assessed numerically, and consequently it has not been possible to quantify the contributions of the individual effects.