bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of polyurethane resins and its improvement on dimensional stability and finishing performances of medium‐ and small‐diameter softwoods
Authors: Lu Kun‐Tsung , Lin Shih‐Ling 
Published: February 2008

AbstractThis study analyzed the effects of polyurethane (PU) resin treatments on surface homogeneity, dimensional stability, and finishing performances of medium‐ and small‐diameter softwoods produced in Taiwan. Two‐pack PU resins were prepared by combing short castor oil‐modified alkyd resin serving as a polyol with polymeric 4,4′‐diphenymethane diisocyanate (PMDI) serving as a hardener, by the molar ratio of NCO/OH+COOH of 1.2. Four types of short oil‐modified alkyd resins with different polyhydric alcohols (glycerin and pentaerythritol) and polybasic acids (phthalic anhydride and isophthalic acid) were synthesized. Three kinds of medium‐ and small‐diameter softwoods, including China fir, Taiwanina, and Japanese fir with a diameter of 10–15 cm were obtained from Hui‐Sun Forest Station, Taiwan. The wood coating of nitrocellulose (NC) lacquer including sanding sealer and top clear was used. Results show that the surface hardness, homogeneity, moisture excluding efficiency, and antiswelling efficiency of woods were enhanced by PU resin treatments. Among all the PU resins, the isophthalic acid and pentaerythritol‐containing PU resin (IPA‐P‐MDI) achieved the best improved efficiency on dimensional stability of woods. Results of two types of finishing procedure, i.e. NC lacquer sanding sealer plus top clear and top clear only, applied onto the PU‐treated woods revealed that the hardness, adhesion, and durability of NC lacquer films on the PU‐treated wood were superior to those of untreated one, especially for top clear finishing alone. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Dynamic mechanical analysis of urea–formaldehyde resin adhesives with different formaldehyde‐to‐urea molar ratios
Authors: Park Byung‐Dae , Kim Jae‐Woo 
Published: February 2008

AbstractAs a part of abating formaldehyde emissions of urea–formaldehyde (UF) resin adhesives, using dynamic mechanical analysis (DMA), we attempted to investigate the influence of the formaldehyde to urea (F/U) molar ratio on the thermomechanical curing of UF resin adhesives with different F/U molar ratios. The thermomechanical curing of these UF resin adhesives was characterized with DMA parameters such as the gel temperature, maximum storage modulus, peak temperatures of the storage and loss moduli, and maximum tan δ. As the F/U molar ratio decreased, the gel temperature of UF resin adhesives increased, whereas the maximum storage modulus, an indicator of the rigidity of UF resin adhesives, decreased. The maximum tan δ increased with the F/U molar ratio decreasing, and this indicated that the UF resin adhesive with a low F/U molar ratio had greater damping than the one with a high F/U molar ratio. A decrease in the rigidity of the UF resin with a lower F/U molar ratio was explained by the calculated crosslinking density, which decreased with the F/U molar ratio decreasing. These results partially explained why UF resin adhesives with lower F/U molar ratios showed relatively poor adhesion performance when they were applied to the manufacture of wood panels. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis of an amide/carboxylate copolymer for barium titanate suspensions. I. As a dispersant
Authors: Chen Lung‐Pin , Hsu Kung‐Chung 
Published: February 2008

AbstractAn anionic copolymer, that is, poly[methacrylamide‐co‐(ammonium methacrylate)] (PMMN), was synthesized for the purpose of application to barium titanate (BT) suspensions. The chemical structure of the prepared polymer was verified with IR and 1H‐NMR spectra. PMMN has the potential to have a double function of dispersant and binder for BT suspensions because it contains both amide groups, which are expected to bring a binder contribution, and carboxylate groups, which are expected to bring a dispersant contribution. In this article, the dispersion effects of PMMN with different monomer ratios are examined and evaluated through viscosity and sedimentation measurements. The results indicate that this polymer could uniformly disperse the particles and make the resulting suspensions less viscous and more stabilized. PMMN with a methacrylamide/ammonium methacrylate ratio of 60/40 appears to be most effective, as this polymer induces sufficient electrostatic forces among particles when it is adsorbed onto BT powder. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
A simple imide compound as a curing agent for epoxy resin. I. Synthesis and properties
Authors: Wu Wan‐Lung , Hsu Kung‐Chung , Cheng Wu‐Hsun 
Published: February 2008

AbstractA simple imide compound, 4‐amino‐phthalimide (APH), was synthesized as a curing agent for epoxy resin. APH was prepared from the hydration of 4‐nitro‐phthalimide, which was prepared from the nitration of phthalimide. The chemical structure of APH was verified by IR and 1H‐NMR spectra. The thermal properties and dielectric constant (ε) of a phosphorus‐containing novolac epoxy resin cured by APH were determined and compared with those of epoxy resins cured by either 4,4′‐diamino diphenyl methane (DDM) or 4,4′‐diamino diphenyl sulfone (DDS). The results indicate that the epoxy resin cured by APH showed better thermal stability and a lower ε than the polymer cured by either DDM or DDS. This was due to the introduction of the imide group of APH into the polymer structure. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis, characterization, and photophysics of a novel conjugated polymer with 1,3,4‐oxadiazole, carbazole, and naphthalene units
Authors: Feng Liheng , Wang Xiaoju , Chen Zhaobin 
Published: February 2008

AbstractA polymer containing 1,3,4‐oxadiazole and carbazole units in the main chain and naphthalene moieties as side groups (P‐OCN) was synthesized by the Wittig reaction of [2,5‐bis(3‐tolylene)1′,3′,4‐oxadiazole]‐9‐(α‐naphthyl)‐carbazole polymer (P‐OCN). The optical properties were investigated with ultraviolet–visible absorption and fluorescence emission spectra. The results showed that the luminescence quantum yield of P‐OCN was 0.673 in chloroform, and it emitted blue and blue‐green light with a band gap of 3.49 eV estimated from the onset absorption. Thermogravimetric analysis and differential scanning calorimetry showed that the polymer exhibited good thermal stability up to 354°C with a glass‐transition temperature higher than 110°C. To investigate the donating and accepting capacities of P‐OCN, the fluorescent quenching technique was used to determinate the interactions between the polymer and the electron donor and electron acceptor. The results showed that the light emission could be quenched by both the electron donor (N,N‐dimethylaniline) and electron acceptor (dimethylterephthalate). Furthermore, the interaction between P‐OCN and fullerene was also studied with fluorescent quenching, and the processes followed the Stern–Volmer equation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Mechanical and surface properties of polyurethane/fluorinated multi‐walled carbon nanotubes composites
Authors: Deng Jinni , Cao Jing , Li Jiehua , Tan Hong , Zhang Qin , Fu Qiang 
Published: February 2008

AbstractTo improve the mechanical and surface properties of poly(etherurethane) (PEU), multi‐walled carbon nanotubes (MWCNTs) were surface grafted by 3,3,4,4, 5,5,6,6,7,7,8,8,8‐tridecafluoro‐1‐octanol (TDFOL) (MWCNT‐TDFOL) and used as reinforcing agent for PEU. Fourier‐transform infrared spectroscopy revealed the successful grafting of MWCNTs. PEU filled with MWCNT‐TDFOL could be well dispersed in tetrahydrofuran solution, and tensile stress–strain results and dynamic mechanical analysis showed a remarkable increase in mechanical properties of PEU by adding a small amount of MWCNT‐TDFOL. Contact angle testing displayed a limited improvement (just 9°) in the hydrophobicity of PEU surface by solution blending with MWCNT‐TDFOL. However, a large improvement of surface hydrophobicity was observed by directly depositing MWCNT‐TDFOL powder on PEU surface, and the water contact angle was increased from 80° to 138°. Our work demonstrated a new way for the modification of carbon nanotubes and for the property improvement of PEU. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Modeling of a fluidized bed propylene polymerization reactor operated in condensed mode
Authors: Utikar Ranjeet P. , Harshe Yogesh M. , Mehra Anurag , Ranade Vivek V. 
Published: February 2008

AbstractThe gas‐phase polymerization of propylene is one of the most widely accepted and commercially used processes for the manufacture of polypropylene (PP). Because of the highly exothermic nature of polymerization reactions, temperature runaway and subsequent polymer melting and agglomeration may occur, and the reactor has to be operated in a small operating window for safety. The addition of liquid monomer for heat removal (condensed mode) broadens the operating window and can substantially increase (by 50–100%) the capacity of given reactor hardware. This article describes the extension of a comprehensive mathematical model for the simulation of fluidized bed PP reactors to include the condensed mode of operations. The model is used to determine the influence of the operating parameters on the polymer properties and particle size distribution. The model is also used to determine the effects of two active sites and the reaction kinetics on macroscopic variables. The developed framework is useful for simulating multimonomer, multisite Ziegler–Natta‐type olefin fluidized bed polymerization reactors operated under condensed mode. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
New toughened polypropylene/organophilic montmorillonite nanocomposites
Authors: Li Peiyao , Song Guojun , Yin Lanlan , Wang Li , Ma Guiping 
Published: February 2008

AbstractA new toughened polypropylene (PP)/organophilic montmorillonite (OMMT) nanocomposite was obtained by melt intercalation extrusion in a twin‐screw extruder without any compatibilizer. The nanocomposites were characterized by transmission electron microscopy (TEM) observation, melt flow rate (MFR) testing, mechanical properties measurement, melting and crystallization behaviors, and thermal stability determination. TEM images revealed the existence of intercalated OMMT layers dispersed throughout the PP matrix. A clear reduction in MFR was observed as the OMMT content increased. The yield strength, elongation at yield, and initial modulus of the PP/OMMT nanocomposites increased slightly as the result of the reinforcement of the OMMT nanofiller. The ultimate value of notched impact strength of the nanocomposites was over twofold that of neat PP after incorporation with 4 wt % OMMT; meanwhile, the heat deflection temperature values showed that the thermal stability increased a little. This is a new approach for preparation for the production of a toughened PP material with a high thermal stability and rigidity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Morphology of polyvinylidenefluoride and the copolymer of tetrafluoroethylene with ethylene using thermomechanical analysis
Authors: Olkhov Yu. A. , Allayarov S. R. , Konovalova T. A. , Kispert L. D. , Nikles D. E. 
Published: February 2008

AbstractThe morphology of polyvinylidenefluoride (PVDF) and the copolymer of tetrafluoroethylene with ethylene (CTE) were investigated by thermomechanical analysis. Both granules and highly dispersed powders of the polymers have similar morphology. Polymer granules contain amorphous and crystalline regions. The morphology of the polymer powders were determined under two analytical conditions: coaxial, when the vectors of polymer loading and vector of compression pressure are in the same plane, or when they are perpendicular to each other. One amorphous and two crystal blocks were found at coaxial orientations of the vectors. Thermomechanical analysis showed that the polymers had a completely amorphous diblock morphology at the perpendicular orientation of the vectors. Parameters that characterize a degree of interchain interaction, such as coefficients of thermal expansion, free volume, and temperatures of polymer transformation into the glassy, high‐elastic, or flow‐viscous state were determined. PVDF and CTE have similar topographic composition, but different molecular mass and temperatures of phase transitions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Blends of poly(L‐lactic acid) with poly(ω‐pentadecalactone) synthesized by enzyme‐catalyzed polymerization
Authors: Nakane Koji , Tamaki Chiharu , Hata Yoshihiro , Ogihara Takashi , Ogata Nobuo 
Published: February 2008

AbstractPoly(ω‐pentadecalactone) (PPDL) was synthesized by enzyme‐catalyzed polymerization. The molecular weight of the PPDL was about 35,000. Opaque poly(L‐lactic acid) (PLLA)/PPDL blend films were created by the solvent casting technique. The addition of PPDL led to PLLA crystallization. Furthermore, the addition of PPDL with PLLA increased both the Young's modulus [pure PLLA : 0.67 GPa, PLLA/PPDL (70/30 wt %) : 1.01 GPa] and the PLLA glass transition temperature. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Mechanical properties of polylactide after repeated cleanings
Authors: Karst David , Hain Michelle , Yang Yiqi 
Published: February 2008

AbstractThe ability of polylactide (PLA) to retain its mechanical properties after repeated cleanings at various pH levels, washing temperatures, and drying conditions has been studied. One of the problems with PLA is its poor resistance to hydrolysis, especially under alkaline conditions. In this study, PLA fabrics were sent through 50 cleaning cycles with different pH levels (8 or 10), washing temperatures (35 or 55°C), and drying conditions (air dry at 21°C/65% relative humidity or tumble dry at 50 or 70°C). The retention percentages of the breaking tenacity, breaking elongation, and modulus of the PLA yarns were measured after every 10 cleaning cycles. A pH of 8 gave greater breaking tenacity, breaking elongation, and modulus retention than pH 10. Washing PLA at 35°C and air drying it at 21°C resulted in greater modulus retention than washing and drying at higher temperatures. Hydrolysis of the polymer was the main cause of the loss in mechanical properties. Equations were developed to predict the retention percentage of the breaking tenacity, breaking elongation, and modulus based on the pH, number of cleaning cycles, and washing and drying temperatures. Recommendations for appropriate conditions for the cleaning of PLA fabrics that result in greater mechanical property retention are given. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Ontology‐based speech act identification in a bilingual dialog system using partial pattern trees
Authors: Yeh Jui‐Feng , Wu Chung‐Hsien , Chen Ming‐Jun 
Published: February 2008

AbstractThis article presents a bilingual ontology‐based dialog system with multiple services. An ontology‐alignment algorithm is proposed to integrate ontologies of different languages for cross‐language applications. A domain‐specific ontology is further extracted from the bilingual ontology using an island‐driven algorithm and a domain corpus. This study extracts the semantic words/concepts using latent semantic analysis (LSA). Based on the extracted semantic words and the domain ontology, a partial pattern tree is constructed to model the speech act of a spoken utterance. The partial pattern tree is used to deal with the ill‐formed sentence problem in a spoken‐dialog system. Concept expansion based on domain ontology is also adopted to improve system performance. For performance evaluation, a medical dialog system with multiple services, including registration information, clinic information, and FAQ information, is implemented. Four performance measures were used separately for evaluation. The speech act identification rate was 86.2%. A task success rate of 77% was obtained. The contextual appropriateness of the system response was 78.5%. Finally, the rate for correct FAQ retrieval was 82%, an improvement of 15% over the keyword‐based vector‐space model. The results show the proposed ontology‐based speech‐act identification is effective for dialog management.
Hjørland's critique of bates' work on defining information
Authors: Bates Marcia J. 
Published: February 2008

AbstractIn a recent article, Birger Hjørland (2007) critiqued the author's efforts in defining and conceptualizing information as a core concept in information science (Bates, 2005, 2006). It is argued that Hjørland has seriously misrepresented and confused the actual line of argument in those articles. Specifics of that case are presented, and the reader is urged to return to the original Bates articles to understand her claims. In those articles, Bates attempted to develop a broad conception of information, as well as a number of subtypes of information, for use in the field of information science. The development of information was related to evolutionary processes, with emergence as a significant theme.
Zum Einfluss der Nietkopfabrostung auf die Nietvorspannung und Dauerhaftigkeit alter Stahlkonstruktionen
Authors: Feldmann Markus , Heinemeyer Christoph , Hinrichs Hauke 
Published: February 2008

AbstractNicht selten sind bei genieteten Brücken die Niete selbst markante Punkte des Korrosionsangriffs. So sind die Korrosionserscheinungen besonders an den Köpfen der Niete in Form von Abrostungen etc. zu beobachten. Dies wirft die Frage auf, ab wann und inwieweit die Nietvorspannung durch die Materialabtragung abgemindert wird, so dass mit einer Beeinträchtigung des Trag‐ und Ermüdungsverhaltens zu rechnen ist. In dem folgenden Beitrag wird der Vorspann‐ und Klemmzustand von Nietungen in Abhängigkeit von einem durch Korrosion reduzierten Restquerschnitt des Nietkopfs vorgestellt. Dabei werden in experimentellen Untersuchungen, die durch numerische Untersuchungen ergänzt werden, die Abrostungen durch Fräsungen am Nietkopf simuliert. Durch weitere Versuche gelingt es, eine Prognose der Ermüdungsfestigkeiten in Abhängigkeit des durch die Nietkopfabrostung verursachten Vorspannungsabfalls und der dadurch bedingten verstärkten Spannungsspitzen im Blech abzugeben.
Sanierung und Verstärkung von Gründungsbauteilen
Authors: Dehn Frank , Gebhardt Matthias , Pollnow Elke 
Published: February 2008

AbstractDie Bedeutung des Bauens im Bestand wird in den nächsten Jahren, gemessen am Gesamtbauvolumen, weiter zunehmen. Insbesondere steht die öffentliche Hand vor der großen Herausforderung, eine Vielzahl historischer, denkmalgeschützter Bauten vor weiterem Verfall zu bewahren und möglichst einer Nutzung zuzuführen.Viele dieser Bauwerke weisen eine Vielzahl “üblicher” Schadensbilder wie Durchfeuchtungen, Holzschäden, Deformationen und Rissbildungen auf. Oft deuten charakteristische Verformungen und Rissbilder auf die Gründung als eine der möglichen Schadensursachen hin. Anhand geotechnischer Untersuchungen und Nachweise ist festzustellen, inwieweit die Schadensursache der Gründung und/oder dem Baugrund zuzuordnen ist und in welchem Umfang die Standsicherheit des Bauwerks gefährdet bzw. die Funktionsfähigkeit in unzulässiger oder nicht mehr zu tolerierender Art und Weise beeinträchtigt wird.Der Beitrag zeigt an ausgewählten Beispielen aus der Ingenieurpraxis Vorgehensweise und konstruktive Möglichkeiten, die sowohl zur Sanierung wie auch zur Verstärkung von Gründungsbauteilen anwendbar sind.
Schraubpfähle: Herstellung, Tragfähigkeit und numerische Modellierung
Authors: Vermeer Pieter , Bernecker Oliver , Weirich Tim 
Published: February 2008

AbstractSchraubpfähle stellen als Verdrängungspfähle eine interessante Alternative zu den herkömmlichen gebohrten Pfahlsystemen (z. B. Bohrpfähle, Schneckenbohrpfähle) dar, deren Herstellprozess immer mit einer Störung des anstehenden Bodens verbunden ist, was zu einem negativen Einfluss auf die Pfahltragfähigkeit führt. Die Tragfähigkeiten der mehr oder weniger als vollverdrängend einzustufenden Schraubpfähle sind vergleichbar mit denen von Rammpfählen. Eine vibrationsfreie und geräuscharme Herstellung lassen einen Einsatz des Systems auch dort zu, wo gerammte Pfähle nicht geeignet sind. Die als vollverdrängende Systeme hergestellten Schraubpfähle bieten auch aus umwelttechnischen Gesichtspunkten interessante Vorteile.Diese relativ neue Pfahlherstelltechnik wird bereits erfolgreich als effizientes Gründungssystem eingesetzt, das den Anforderungen an eine sichere und herstellfreundliche Gründung gerecht wird. Der Einsatz von üblichen, kompakten Maschinen mit hoher Produktivität fördert eine wirtschaftlich effiziente Ausführung.Dieser Beitrag stellt das System Schraubpfähle vor und beschreibt die Herstellung und deren Einfluss auf die Tragfähigkeit. Es wird die zu erwartende Tragfähigkeit anhand von Widerstand‐Setzungs‐Linien diskutiert. Ein erster Ansatz zur numerischen Modellierung von Schraubpfählen wird anhand von Vergleichsberechnungen vorgestellt.
Antibacterial hydrogels of amino acid‐based cationic amphiphiles
Authors: Roy Sangita , Das Prasanta Kumar 
Published: February 2008

AbstractDevelopment of biomaterials, which are inherently antibacterial having broad‐spectrum activity against both Gram‐positive and Gram‐negative bacteria with considerable biocompatibility, is of tremendous importance in biomedicinal chemistry. Microbial infections are still of great concern, often originated from indwelling medical devices typically in hospitalized patients. To this end, hydrogelating soft materials particularly from low‐molecular‐weight (LMW) gelators have generated significant interest in preparing and modifying biomedicinal implants. Herein, we have developed L‐tryptophan based cationic amphiphilic hydrogelators with varying degree of hydrophobicity that exhibited remarkable bactericidal activity against wide range of Gram‐positive (MIC = 0.1–75 µg/mL) and Gram‐negative bacteria (MIC = 0.5–5 µg/mL). Antimicrobial efficacy of the amphiphiles was greatly influenced by their alkyl chain length. This bactericidal effect of cationic hydrogelators is quite comparable or in some cases markedly better than that of clinically available antibiotics. Most excitingly, they selectively attack the bacterial pathogens while remain biocompatible to the mammalian cells. Thus, we have developed LMW biocompatible, inherently antibacterial hydrogels having potential applications in biomedicines. Biotechnol. Bioeng. 2008;100: 756–764. © 2008 Wiley Periodicals, Inc.
A hybrid‐Trefftz finite element model for Helmholtz problem
Authors: Sze K. Y. , Cheung Y. K. 
Published: February 2008

AbstractIn this paper, a hybrid‐Trefftz four‐node quadrilateral element model is formulated for Helmholtz problem. In this model, two Helmholtz approximations are defined. The first approximation is obtained by nodal interpolation, and the second approximation is truncated from a Trefftz solution set. A hybrid variational functional is employed to enforce the equality of and other necessary conditions on the two approximations. From the numerical tests, it can be seen that the hybrid model is markedly more accurate than the conventional finite element model. Copyright © 2008 John Wiley & Sons, Ltd.
Design of current‐mode MOSFET‐C filters using OTRAs
Authors: Hwang Yuh‐Shyan , Wu Dong‐Shiuh , Chen Jiann‐Jong , Shih Chun‐Chi , Chou Wen‐Shou 
Published: February 2008

AbstractIn this paper, third‐order current‐mode MOSFET‐C filters that use operational transresistance amplifiers (OTRAs) with little parasitic capacitance effects are presented. On the basis of the proposed systematic method and design procedure, we can efficiently synthesize third‐order active filters with OTRAs along with simplified MOSFET resistor circuits, and all virtually grounded capacitors. Third‐order current‐mode Chebychev low‐pass and high‐pass filters are realized to verify the validity of the theoretical analysis. Experimental results employing commercially available current feedback amplifiers are also given. Copyright © 2008 John Wiley & Sons, Ltd.