bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies of Partially Metallated Poly(2‐vinylfluorene)'s in Solution 1 ‐ Ion Pair Structure and the Concentration Effects of Carbanion Salts Along the Polymer Chain
Authors: Watanabe Akira , Matsuda Minoru 
Published: April 2007

AbstractPartially metallated polymers of 2‐vinylfluorene in tetrahydrofuran THF and THF‐dimethoxyethane mixtures were studied by electronic absorption spectroscopy. Effects arising from interaction of the ion pairs within the polymer chain were clearly observed. Conversion of the contact ion pairs with lithium and sodium cations into the solvent‐separated ion pairs is influenced by interactions between the solvent‐separated ions pairs. The polymer carbanions with bulky K+ and Cs+ cations exhibited a shift of λ with increasing carbanion concentration, suggesting the formation of an extended polymer chain in solution.
Size Exclusion Chromatography of Poly(ethylene glycol)
Authors: Güven Olgun 
Published: April 2007

AbstractSize exclusion chromatography calibrations for polystyrene and poly(ethylene glycol) standard samples in the molecular weight range of (600‐11000) have been obtained in tetrahydrofuran. The Kuhn‐Mark‐Houwink‐Sakurada constants of poly(ethylene glycol) in tetrahydrofuran were determined, and poly(ethylene glycol) chromatograms were evaluated according to primary and universal calibration methods. The molecular weights determined from universal curves were substantially lower than those obtained from primary curves. The Coll and Prusinowski universal calibration procedure gave better results than the calibration of Benoit et al.
Synthesis, characterization and curing of m‐diethylaminophenol‐formaldehyde resin
Authors: Patel Pradip S. , Patel Shanti R. 
Published: April 2007

AbstractPolycondensation of m‐diethylaminophenol with formaldehyde has been studied under various reaction conditions. The resins formed are fusible and soluble in common organic solvents. All the resin samples have been characterized by spectral studies, measurement of solution viscosity, estimation of M̄n and by t.g.a. The curing of selected resin samples by hexamine has been studied both by measuring percentage of cured material as a function of time at different temperatures and by differential scanning calorimetry. The d.s.c. data have been analyzed by various methods to evaluate the gross kinetic parameters of the curing reactions.
Determination of average molecular weights of a polyelectrolyte by meniscus‐depletion sedimentation equilibrium
Authors: Budd Peter M. 
Published: April 2007

AbstractLong‐column meniscus‐depletion sedimentation equilibrium has been used to determine M̄n, M̄w and M̄z for the Na+ and (CH3)4N+ salts of a high molecular weight poly(styrene sulphonate). Consideration has been given to ways of avoiding the need for dialysis when dealing with polyelectrolyte solutions.
Use of DTA with infrared analysis of evolved gas to investigate the effect of flame retardants on gas evolution from pyrolysed cellulose (cotton)
Authors: Price Dennis , (Dick) Horrocks A. R. , Akalin Mehmet 
Published: April 2007

AbstractDTA combined with infrared analysis of the evolved gas (EGA) has been used to study the temperature behaviour, both in air and nitrogen, of commercial phosphorus‐ and nitrogen‐ and/or bromine‐containing flame retardants applied to cotton. By reference to the DTA traces and also the maxima occurring in the CO, CO2 and H2O evolution rates, seven significant peak temperatures were assigned. Two new relatively low temperature peaks have been observed: the higher of these is DTA‐sensitive and occurs in all unretarded and retarded samples and is ascribed to the formation of an ‘activated cellulose’ state previously proposed by Bradbury, Sakai and Shafizadeh;17 the lower peak is an exotherm (188‐220°C) associated with H2O and CO2 evolution from flame‐retarded samples only. These observations are interpreted in terms of the mechanism of the cellulose pyrolysis/combustion and the influence of the flame retardants.
Ring‐opening polymerization of 1 ‐ethylbicyclo[2.2.1] hept‐2‐ene
Authors: Hamilton James G. , Ivin Kenneth J. , Rooney John J. 
Published: April 2007

Abstract1‐Ethylbicyclo[2.2.1]hept‐2‐ene has been polymerized using a range of metathesis catalysts and the structure of the polymers determined by 13C n.m.r. spectroscopy. For a given catalyst the cis double bond content was lower and the head‐tail bias greater than for polymers of the 1‐methyl analogue. This is interpreted in terms of enhanced steric and polar effects brought about by the ethyl substituent.
Thermal behaviour of films of partially neutralized poly(acrylic acid). 3: Effect of magnesium and calcium ions
Authors: Nicholson John W. , Wasson Eleanor A. , Wilson Alan D. 
Published: April 2007

AbstractPartially neutralized polyacrylates of calcium and magnesium have unexpectedly been found not to undergo thermal decarboxylation at 250°C, unlike partial polyacrylates of lithium, sodium or potassium. Reflectance infrared spectroscopy has confirmed that the partial polyacrylate of calcium is predominantly ionic but as with the magnesium compound, this does not promote decarboxylation. Further study of the partial lithium salt of poly(acrylic acid) has confirmed that lithium ions exhibit some degree of covalency, and hence are probably site‐bound. Despite this, they succeed in promoting decarboxylation. It is concluded that the main factor which prevents calcium and magnesium facilitating decarboxylation is their divalency, rather than any inherent tendency to become site‐bound. Reasons for this are discussed.
Some thermodynamic properties of tetrafluoroethene‐hexafluoropropene copolymers
Authors: Simeone Giovanni , Bonardelli Piergiorgio , Moggi Giovanni , Bart Jan C. J. 
Published: April 2007

AbstractCopolymers of tetrafluoroethene (TFE) with hexafluoropropene (HFP) have been prepared in the 0‐14mol% HFP composition range. Their melting temperatures (Tm), enthalpies (ΔHf) and entropies (ΔSf) of first and second fusion, and crystallinities (X) according to x‐ray diffraction(x.r.d.) and differential scanning calorimetry (d.s.c.) have been determined. The results indicate that ΔHf/Xx.r.d of the polymer crystals decreases with higher HFP content.
Theoretical and experimental considerations on poly(dihalophenylene oxide)s
Authors: Türker Lemi , Kisakürek Duygu 
Published: April 2007

AbstractThe decomposition of copper(II) trihalophenoxides in acetonitrile yields poly(dihalophenylene oxide)s. A 1H n.m.r. study has shown that a bromine atom in the 4‐position of the trihalophenoxides results in polymers having higher linearity. Various dynamic and static methods, within the framework of Hückel molecular orbital theory, have been used to explain the product distribution.
Metal aerosol jet printing for solar cell metallization
Authors: Mette A. , Richter P. L. , Hörteis M. , Glunz S. W. 
Published: April 2007

AbstractMetal aerosol jet printing is a new non‐contact direct‐write technique for the front side metallization of highly efficient industrial silicon solar cells. With this technique the first layer of a two‐layer contact structure is created. It features a low contact resistance and good mechanical adhesion to the silicon surface. The second layer is formed by light‐induced silver plating (LIP) to increase the line conductivity. To form the first layer a metal‐containing aerosol is created in the printer and focused via a second surrounding gas stream through a nozzle and deposited onto the substrate. The focussing gas avoids the contact between the aerosol and the nozzle tip. In addition, line widths significantly smaller than the outlet diameter of the nozzle tip can be reached. Fine and continuous lines with a width of 14 µm were printed using a metal organic ink. As the adhesion of these layers was not sufficient, a commercially available screen‐printing paste for solar cell metallization was modified and tested. Monocrystalline silicon solar cells of 12·5 cm × 12·5 cm with an aluminum back surface field were processed, achieving energy conversion efficiencies up to 17·8%. Copyright © 2007 John Wiley & Sons, Ltd.
Structural and electrical properties of Zn(Al)O layers for transparent metal oxide applications
Authors: Kwon Y. B. , Abouzaid M. , Ruterana P. , Je J. H. 
Published: April 2007

AbstractThe microstructure and electrical properties of low temperature (250 °C) RF sputtered Al doped ZnO layers are investigated. By varying the Al composition from 0 to 15 at%, it is shown that the morphology of the layers is improved whereas the crystalline structure changes from highly oriented monocrystalline domains to textured and misoriented nanocrystallites. It is also noticed that the best metallic properties are attained for a quite low Al concentration in the AZO (3 at%), when the Al content is further increased, the mobility, carrier density and resistivity saturate. The annealing in air at higher temperatures does not seem to improve the conduction properties, instead at 800 °C, the resistivity drops by more than one order of magnitude and the carrier density by almost five orders of magnitude. At this high temperature, the strong increase of the mobility is tentatively attributed to the better crystalline quality of the annealed layers. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A theoretical investigation of ZnOxS1–x alloy band structure
Authors: Rozale H. , Beldi L. , Bouhafs B. , Ruterana P. 
Published: April 2007

AbstractWe report the properties of ordered ZnOx S1–x alloys calculated in various structures (CuAu–I, Cu3Au, Luzonite and Famatinite) using a first‐principles total‐energy formalism based on the hybrid full‐potential augmented plane‐wave plus local orbitals (APW + lo) method, within the local‐density approximation (LDA). The calculated band gaps of the alloys are direct and range from 0.49 for O‐rich to 1.55 eV for S‐rich ZnOx S1–x . The non linear variation of the band gap energy is related to the large electronegativity difference between O and S. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural and optical properties of zinc oxide films deposited by wire explosion technique
Authors: Snitka Valentinas , Jankauskas Vytenis , Žunda Audrius , Mizariene Vida , Seniunas Gediminas 
Published: April 2007

AbstractNanostructured ZnO films were deposited on glass, quartz and Al on silicon mono‐crystal Si (100) substrates by using the wire explosion technique. The growth process, structure and photoluminescence (PL) properties were studied by X‐ray diffraction (XRD), UV–VIS spectroscopy, scanning electron (SEM) and atomic force microscopy (AFM) and photoluminescence measurements. X‐ray diffraction measurements have shown that ZnO films are composed of (100), (002), (101) orientation crystallites. The post‐deposition thermal treatment at 600 °C temperature in air has shown that the composite of Zn/ZnO film was fully oxidized to ZnO film. XRD spectra of the film deposited in oxygen atmosphere at room temperature presents high intensity dominating peak at 2θ = 36.32° corresponding to the (101) ZnO diffraction peak. The small fraction of the film (7%) correspond to (002) peak intensity at 2θ = 34.42°. This result indicates the good crystal quality of the film and hexagonal wurtzite‐type structure deposited by zinc wire explosion. The SEM analysis shows that ZnO films presented different morphologies from fractal network to porous films depending on deposition conditions. AFM analysis revealed the grain size range from 50 to 500 nm. The deposited in air films have shown the weak PL peak at ∼373 nm and a strong green luminescence band. The films deposited in oxygen atmosphere demonstrate increased UV band PL intensity and decreased intensity of green PL band. The obtained PL spectra are similar to powder ZnO and it correlates with the size of ZnO nanoparticles (10–30 nm) measured by AFM. These results demonstrated that the wire explosion technique is a feasible method to produce high‐quality ZnO nanocrystalline thin films and quantum dots. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Involvement of morbilliviruses in the pathogenesis of demyelinating disease
Authors: Sips G. J. , Chesik D. , Glazenburg L. , Wilschut J. , De Keyser J. , Wilczak N. 
Published: April 2007

AbstractTwo members of the morbillivirus genus of the family Paramyxoviridae, canine distemper virus (CDV) and measles virus (MV), are well‐known for their ability to cause a chronic demyelinating disease of the CNS in their natural hosts, dogs and humans, respectively. Both viruses have been studied for their potential involvement in the neuropathogenesis of the human demyelinating disease multiple sclerosis (MS). Recently, three new members of the morbillivirus genus, phocine distemper virus (PDV), porpoise morbillivirus (PMV) and dolphin morbillivirus (DMV), have been discovered. These viruses have also been shown to induce multifocal demyelinating disease in infected animals. This review focuses on morbillivirus‐induced neuropathologies with emphasis on aetiopathogenesis of CNS demyelination. The possible involvement of a morbillivirus in the pathogenesis of multiple sclerosis is discussed. Copyright © 2007 John Wiley & Sons, Ltd.
Automated tether management system for extravehicular activities
Authors: Minor Mark A. , Hirschi Christopher R. 
Published: April 2007

AbstractSafe extravehicular activity (EVA) requires astronauts to employ tethers to ensure proximity to their spacecraft. This research strives to improve EVA efficiency by allowing crew members to remotely release and retract their safety tether from extended distances using a tether management system consisting of a remotely releasable robotic gripper and a retractor that controls the length of tether. This circumvents the current need to travel back to the tether anchor and manually release the tether, which requires the crew member to travel three times further than necessary. The automated tether management system is essentially a multifunctional teleoperated robotic system that has the potential to improve EVA efficiency, reduce crew‐member fatigue, and improve efficiency of existing robots such as Robonaut. Design and performance requirements are specified to comply with current safety standards. The multifunctional gripper is designed to provide fail‐safe self‐locking positive engagement on a variety of spacecraft anchors. The retractor employs motorized and passive retraction to minimize power consumption, allow the retractor to mimic existing retractable safety tethers functionality, and facilitate control over gripper flight. A nonconductive fiber‐optic core structural tether is designed to transmit commands to the gripper while reducing the risk of developing electrical charges at orbital velocities. Experiments in a simulated microgravity environment evaluate behavior during gripper release and retraction and provide guidelines for improved system operation. Based on these guidelines, the system is then further optimized via simulation for improved retraction considering orbital dynamics. These results provide a recommended operating envelope to allow safe automated gripper retraction. © 2007 Wiley Periodicals, Inc.
Sensor architecture for the robotic control of large flexible space structures
Authors: Bilton Amy , Ishijima Yoshiyuki , Lichter Matthew , Dubowsky Steven 
Published: April 2007

AbstractThe future construction and maintenance of very large space structures such as orbital solar power stations and telescopes will require teams of free‐flying space robots. For robots to effectively perform these tasks, they will require knowledge of the structure's vibrations. Here, a robotic based sensor architecture for the vibration estimation of very large structures is presented. It is shown that this information can be effectively estimated by combining data provided by free‐flying remote robot “observers” equipped with range sensors with structure‐mounted acceleration sensors. A modified Kalman filter fuses low‐bandwidth vision data from the remote sensing robots with the high bandwidth, but spatially sparse structure‐mounted acceleration sensors. Results from experimental studies are presented that confirm the effectiveness of this approach. 2007 Wiley Periodicals, Inc.
Efficient support for content‐aware request distribution and persistent connection in Web clusters
Authors: Liu Ho‐Han , Chiang Mei‐Ling , Wu Men‐Chao 
Published: April 2007

AbstractTo support Web clusters with efficient dispatching mechanisms and policies, we propose a light‐weight TCP connection transfer mechanism, TCP Rebuilding, and use it to develop a content‐aware request dispatching platform, LVS‐CAD, in which the request dispatcher can extract and analyze the content in requests and then dispatch each request by its content or type of service requested. To efficiently support HTTP/1.1 persistent connection in Web clusters, request scheduling should be performed per request rather than per connection. Consequently, multiple TCP Rebuilding, as an extension to normal TCP Rebuilding, is proposed and implemented. On this platform, we also devise fast TCP module handshaking to process the handshaking between clients and the request dispatcher in the IP layer instead of in the TCP layer for faster response times. Furthermore, we also propose content‐aware request distribution policies that consider cache locality and various types of costs for dispatching requests in this platform, which makes the resourceutilization of Web servers more effective. Experimental results of a practical implementation on Linux show that the proposed system, mechanisms, and policies can effectively improve the performance of Web clusters. Copyright © 2007 John Wiley & Sons, Ltd.
Self‐deployable structures with “scissor‐like‐elements”: Problems of simulation and control
Authors: Barsotti A. , de Barbieri F. 
Published: April 2007

AbstractThe scope of the work has been to study the static and dynamic behaviour of deployable or self‐deployable structures composed by rigid elements interconnected by pin‐jointed ends and intermediate pivots, that can be assembled in order to form movable roofing systems or similar applications. Modelling of the behaviour of self‐deployable systems has been approached both during the deployment and in the fully deployed configuration. In particular, the non‐linear dynamic simulation of the deployment phase is approached as a coupled problem of dynamics and kinematics leading to a non‐linear model of the system. The problem of applying active control techniques to the resulting system is also faced, leading to the solution of the non‐linear control problem for the deployment phase, and to a bounded ‐state approach for the in‐service phase. Numerical developments have been performed in the MATLAB environment.
Design and test of a multi‐input multi‐output adaptive active flutter suppression system based on neural network for a wing model
Authors: Rendina M. , Mazzoni G. 
Published: April 2007

AbstractThis paper describes the application of a recurrent dynamic neural network to the problem of adaptive active flutter suppression. A significant feature of the neural controller is its application to an unstable and non‐minimum phase system. The development of the system and its experimental verification are carried out on a wing model with two control surfaces, one on the leading and one at the trailing edge, and two accelerometers. The controller combines a first network for the identification of the variables to be controlled, i.e. the two wing tip accelerations at the leading and trailing edge, with a second network, that commands the deflection required to the control surfaces. It is used for the control task using the output generated by the first network. Adaptivity is obtained by maintaining an on‐line training on both of the neural networks. Extensive preliminary numerical simulations have permitted the authors to define the values of the design parameters aimed at the achievement of an optimal compromise between computational requirements and system performances. The results of the application to the real wing model have shown the effectiveness of such a controller in adapting to different operational conditions, extending flutter free envelope of the wing model up to a speed 30% higher than the uncontrolled flutter onset.
Active vibration control of a monopile offshore structure
Authors: Nielsen S. R. K. , Kirkegaard P. H. , Thesbjerg L. 
Published: April 2007

AbstractIn the Danish part of the North Sea monopile platforms with a cylindrical shaft have been used at the exploitation of marginal fields. In the paper a new principle for active vibration control of such structures is suggested. The principle is based on a control of the boundary layer flow around the cylinder of the platform, so the drag force in the generalized Morison equation is increased whenever it is acting in the opposite direction of the cylinder motion, whereas an unchanged drag force is applied, whenever it is acting co‐directionally to the cylinder motion. The inertial force of the wave load is not subjected to control. The increased drag force is obtained by forcing the boundary layers to separate by blowing air into the boundary layer from the inside through small holes in the cylinder surface placed at a relatively large distance from the water surface. The control is specified by the sign of the fluid velocity relative to the platform, and only this quantity need to be measured, which is easily performed by a flow meter fixed to the platform. The efficiency of the described closed loop control system has been verified by model tests in a wave flume in both regular and irregular wave conditions, where reductions in the vibration level of up to 50% have been registered.
Some experiences on vibrations and noise suppression with piezoelectric active control systems
Authors: Ghiringhelli Gian Luca 
Published: April 2007

AbstractIn this paper a research activity, aimed at verifying the possibility of designing active vibration control systems based on piezoelectric devices, is reported. A full analogic controller has been developed to suppress the vibrations in a clamped rectangular flat panel using piezoceramic patches. Vibration reduction tests and their correlations to numerical predictions, based on an integrated piezo‐structural model, are presented. Only simple co‐located direct feed‐back laws have been used to point out problems related to measurements. Self sensing actuators were also tested. The correlation with numerical prediction shows that the adopted approach is capable of supplying a suitable design tool.
Distributed sensor for detection of impending structural failure along a 25km optical fibre with 2 metres spatial resolution
Authors: Lecœuche V. , Webb D. J. , Pannell C. N. , Jackson D. A. 
Published: April 2007

AbstractWe describe an experimental set‐up designed for detection of impending structural failure in large‐scale structures such as bridges or dams. Strain applied on any 2 metres section along a 25km standard telecommunication fibre can be detected. We demonstrate sufficient signal to noise ratio with a very limited number of acquisitions, which could be performed in less than 3 seconds with custom‐build electronics. All electrical instrumentation is located on one end of the sensing fibre, permitting an easy installation.