bluuebunny/crossref_metadata_2025_split huggingface dataset:
Waiting time analysis for a queueing system with time‐limited service and exponential timer
Authors: Katayama Tsuyoshi 
Published: October 2004

AbstractWe consider a single‐queue with exhaustive or gated time‐limited services and server vacations, in which the length of each service period at the queue is controlled by a timer, i.e., the server serves customers until the timer expires or the queue becomes empty, whichever occurs first, and then takes vacations. The customer whose service is interrupted due to the timer expiration may be attended according to nonpreemptive or preemptive service disciplines. For the M/G/1 exhaustive/gated time‐limited service queueing system with an exponential timer and four typical preemptive/nonpreemptive service disciplines, we derive the Laplace—Stieltjes transforms and the moment formulas for waiting times and sojourn times through a unified approach, and provide some new results for these time‐limited service disciplines. © John Wiley & Sons, Inc. Naval Research Logistics 48: 638–651, 2001.
Allocation of quality improvement targets based on investments in learning
Authors: Moskowitz Herbert , Plante Robert , Tang Jen 
Published: October 2004

AbstractPurchased materials often account for more than 50% of a manufacturer's product nonconformance cost. A common strategy for reducing such costs is to allocate periodic quality improvement targets to suppliers of such materials. Improvement target allocations are often accomplished via ad hoc methods such as prescribing a fixed, across‐the‐board percentage improvement for all suppliers, which, however, may not be the most effective or efficient approach for allocating improvement targets. We propose a formal modeling and optimization approach for assessing quality improvement targets for suppliers, based on process variance reduction. In our models, a manufacturer has multiple product performance measures that are linear functions of a common set of design variables (factors), each of which is an output from an independent supplier's process. We assume that a manufacturer's quality improvement is a result of reductions in supplier process variances, obtained through learning and experience, which require appropriate investments by both the manufacturer and suppliers. Three learning investment (cost) models for achieving a given learning rate are used to determine the allocations that minimize expected costs for both the supplier and manufacturer and to assess the sensitivity of investment in learning on the allocation of quality improvement targets. Solutions for determining optimal learning rates, and concomitant quality improvement targets are derived for each learning investment function. We also account for the risk that a supplier may not achieve a targeted learning rate for quality improvements. An extensive computational study is conducted to investigate the differences between optimal variance allocations and a fixed percentage allocation. These differences are examined with respect to (i) variance improvement targets and (ii) total expected cost. For certain types of learning investment models, the results suggest that orders of magnitude differences in variance allocations and expected total costs occur between optimal allocations and those arrived at via the commonly used rule of fixed percentage allocations. However, for learning investments characterized by a quadratic function, there is surprisingly close agreement with an “across‐the‐board” allocation of 20% quality improvement targets. © John Wiley & Sons, Inc. Naval Research Logistics 48: 684–709, 2001
TEMPOL, a radical scavenger, reduces thermal hyperalgesia and NADPH‐d expression in the neurons of trigeminal ganglion of rats with infraorbital nerve constriction
Authors: Corsetti Giovanni , Rodella Luigi , Rezzani Rita , Bianchi Rossella 
Published: October 2004

AbstractNo medical or surgial treatments have been reported to permanently stop trigeminal pain attacks. TEMPOL, a stable nitroxide radical scavenger, has been recently shown efficient in providing neuroprotection. Here we tested the efficiency of TEMPOL in alleviating heat hyperalgesia and expression of NADPH‐d in trigeminal afferent neurons of rats with experimentally induced secondary trigeminal neuralgia by chronic constriction of infraorbitary nerve. The results showed that TEMPOL significantly reduced heat hyperalgesia and induced a large decrease of NADPH‐d in neurons of the Gasser ganglia. These findings suggest that the radical scavengers like TEMPOL could be new therapeutic strategies to treat neuropathic pain induced by infraorbital nerve constriction.
Polymers containing formamidine groups. VI. Structural influences on the formation of cyclic trimers
Authors: Kunert Christoph , Voigt Dieter , Friedel Peter , Komber Hartmut , Böhme Frank 
Published: October 2004

AbstractThe reaction of different metasubstituted aromatic diamines with triethylorthoformate (TEOF) was investigated. Whereas the conversion of 1,3‐phenylenediamine 1a resulted in an oligomeric polyformamidine, the formation of cyclic trimers was observed when nitrogen‐containing aromatic diamines such as 2,6‐diaminopyridine 1b, 2,4‐diaminopyrimidine 1c, and 2,4‐diamino‐6‐methyl‐1,3,5‐triazine 1d were used. The extent of cyclization depended on the number of nitrogen atoms in the aromatic ring and could be attributed to energetically favored conformations of the chain segments. In the case of 1b, cyclization was quantitative. The results were supported by a conformational analysis concerning the rotational barriers of the aromatic rings in the respective dimers. The reaction products were characterized by means of NMR and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometric investigations. In the reaction product of 1d, strong hydrogen‐bonded associates between the oligomers and the monomer were observed. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1280–1287, 2001
The tenth anniversary of Suzuki polycondensation (SPC)
Authors: Schlüter A. D. 
Published: October 2004

AbstractThis article describes the successful transfer of the Suzuki cross‐coupling (SCC) reaction to polymer synthesis, one of the major developments within the last decade of polymer synthesis. The polymers prepared by Suzuki polycondensation (SPC) and its Ni‐catalyzed reductive counterpart are soluble and processable poly(arylene)s that, because of their rigid and conjugated backbones, are of interest for the materials sciences. Achievable molar masses easily compete with those of traditional polyesters and polyamides. This article also provides insight into some synthetic problems associated with the transfer of SCC from low molar mass organic chemistry to high molar mass polymer chemistry by addressing issues such as monomer purity, stoichiometric balance, achievable molar masses, and defects in the polymer structure. Although the emphasis of this article is synthetic and structural issues, some potential applications of the polyarylenes obtained are briefly mentioned. Together with the enormous developments in the areas of metallocene, ring‐opening metathesis, and acyclic diene metathesis polymerization, the success of SPC impressingly underlines the increasing importance of transition‐metal‐catalyzed CC‐bond‐forming reactions in polymer synthesis. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1533–1556, 2001
Synthesis and kinetics of polymerization of hydrophilic monomers: 2,3‐dihydroxypropylacrylate and 2,3‐dihydroxypropylmethacrylate
Authors: García F. , de la Peña J. L. , Delgado J. J. , García N. , Guzmán J. , Riande E. , Calle P. 
Published: October 2004

AbstractUnsaturated monomers containing none, one, or two hydroxyl groups were obtained by the reaction of glycerol (1,2,3‐trihydroxypropane) with acrylic and methacrylic chloride. The experimental values of the mole fractions of the different monomers were compared with those theoretically obtained by considering different mechanisms involving two or seven kinetic constants. Agreement between the theoretical and experimental results could only be achieved by assuming that the reactivity of the hydroxyl groups changed with the presence of the substituents. The investigation of the radical polymerizations 2,3‐dihydroxypropylacrylate (GA) and 2,3‐dihydroxypro‐ pylmethacrylate (GM) was carried out at several temperatures in water–dioxane solutions. Ultraviolet spectroscopic techniques were used to determine the kinetic constants, and the results were compared with those obtained in the same conditions for methyl acrylate, methyl methacrylate, 2‐hydroxyethylacrylate, and 2‐hydroxyethylmethacrylate. The values of the ratio kp/kt1/2 for the methacrylic monomer GM were higher than 0.5 L1/2 mol−1/2 s−1/2 at temperatures between 50 and 65 °C. These values exceeded 2 L1/2 mol−1/2 s−1/2 for the acrylic monomer GA, perhaps the highest values reported for this kind of monomer. Electron paramagnetic resonance spectroscopy was also used to study the polymerization of GM. All the polymers were soluble in the reaction mixture until very high conversions, and the gel effect was never detected at monomer concentrations equal to or lower than 1 mol L−1. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1843–1853, 2001
Novel approach to well‐defined polyester by living anionic alternating copolymerization of ethylphenylketene with 4‐methoxybenzaldehyde
Authors: Nagai Daisuke , Sudo Atsushi , Sanda Fumio , Endo Takeshi 
Published: October 2004

AbstractA living anionic alternating copolymerization of ethylphenylketene (EPK) with 4‐methoxybenzaldehyde (MBA) was achieved. When n‐butyllithium was added to a mixture of EPK and MBA in tetrahydrofuran at −40 °C in the presence of an excess amount of lithium chloride, the copolymerization of these monomers proceeded via complete 1:1 alternating manner to afford the polymer with a narrow molecular weight distribution. A linear relationship was observed between the molecular weight and the monomer/initiator ratio, keeping a narrow molecular weight distribution. The structure of the obtained polymer was determined to be a polyester by IR spectroscopy together with the reductive degradation of the polymer by lithium aluminum hydride, which quantitatively afforded the corresponding diol to the repeating unit of the expected polyester structure. Both conversions of EPK and MBA agreed to a first‐order kinetic equation with linear evolution between the molecular weight and conversion. These observations along with the successful results in two‐stage polymerization indicate that the present copolymerization proceeded through a living mechanism. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2078–2084, 2001
Preparation and application of a novel core–shell‐particle‐supported zirconocene catalyst
Authors: Liu Chengbin , Tang Tao , Huang Baotong 
Published: October 2004

AbstractThe use of functional groups bearing silica/poly(styrene‐co‐4‐vinylpyridine) core–shell particles as a support for a zirconocene catalyst in ethylene polymerization was studied. Several factors affecting the behavior of the supported catalyst and the properties of the resulting polymer, such as time, temperature, Al/N (molar ratio), and Al/Zr (molar ratio), were examined. The conditions of the supported catalyst preparation were more important than those of the ethylene polymerization. The state of the supported catalyst itself played a decisive role in both the catalytic behavior of the supported catalyst and the properties of polyethylene (PE). IR and X‐ray photoelectron spectroscopy were used to follow the formation of the supports. The formation of cationic active species is hypothesized, and the performance of the core–shell‐particle‐supported zirconocene catalyst is discussed as well. The bulk density of the PE formed was higher than that of the polymer obtained from homogeneous and polymer‐supported Cp2ZrCl2/methylaluminoxane catalyst systems. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2085–2092, 2001
Application of ketenes to well‐defined polyester synthesis. II. Synthesis of reactive polyester by living anionic polymerization of (4‐halophenyl)ethylketene
Authors: Sudo Atsushi , Uchino Satoshi , Endo Takeshi 
Published: October 2004

AbstractNovel ketenes, (4‐chlorophenyl)ethylketene and (4‐bromophenyl)ethylketene, were synthesized by dehydrochlorination of 2‐(4‐halophenyl)butanoyl chlorides, and their anionic polymerizations by lithium (4‐methoxyphenoxide) in tetrahydrofuran at −20 °C were carried out to afford the corresponding polyesters with narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight < 1.3) quantitatively. Polymerizations with various feed ratios afforded the corresponding polyesters with predictable molecular weights and narrow molecular weight distributions. Kinetic studies of the polymerizations at −78 °C revealed that the polymerization rates were apparently larger than that of ethylphenylketene, which is considered to be responsible for the enhanced electrophilicities of the monomers via the introduction of electron‐negative halogen atoms. Monomer conversion agreed with the first‐order kinetic equation. These results strongly support the living mechanism of this polymerization. The obtained polyesters were modified by a palladium‐catalyzed coupling reaction of the side‐chain 4‐halophenyl group with 4‐methoxyphenylboronic acid, demonstrating their potential as reactive polymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2093–2102, 2001
Synthesis of poly(phenylsilsesquioxane) having organostannyl groups
Authors: Matsubara Yasutaka , Konishi Wakako , Sugizaki Toshio , Moriya Osamu 
Published: October 2004

AbstractPoly(phenylsilsesquioxane) (PSQ) having tributylstannyl groups (TBPSQ) was prepared from phenyltrimethoxysilane and bis(tributyltin) oxide [(Bu3Sn)2O] under basic conditions. The procedure, using a catalytic amount of basic reagent such as triethylamine, sodium hydroxide, or aqueous ammonia, afforded yields of TBPSQ based on Si in the range of 12–45% at a number‐average molecular weight precipitated from ethanol of about 3500. In the other procedure, starting from PSQ with (Bu3Sn)2O, the incorporation of tributylstannyl groups into PSQ proceeded effectively in the presence of an acid catalyst such as methanesulfonic acid or sulfuric acid, giving TBPSQ in moderate yields of greater than 52%. Dibutyltin oxide, a bifunctional organotin compound, was also used, affording dibutylstannylated poly(phenylsilsesquioxane) (DBPSQ) without crosslinking. The highest ratio of Si and Sn contained in TBPSQ or DBPSQ, prepared under acidic conditions, was Si/Sn = 7/1. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2125–2133, 2001
Synthesis and characterization of high molecular weight branched PBA
Authors: Han Yang‐Kyoo , Um Jae Won , Im Seung Soon , Kim Byoung Chul 
Published: October 2004

AbstractWe prepared carboxylic acid group terminated linear polybutylene adipate (PBA) by melt polycondensation of adipic acid with 1,4‐butanediol in the presence of titanium(IV) isopropoxide (TIP) as a catalyst. High molecular weight branched PBAs were synthesized through the branching reaction between the carboxylic acid group terminated PBA and branching agent such as glycerol or pentaerythritol in the presence of TIP. The weight‐average molecular weights of the branched PBAs were found to be in the range of about 100,000–240,000 by gel permeation chromatography. Mechanical properties of the linear and branched PBAs were measured on an Instron tensile tester. The moduli of the branched PBAs had lower values of 320–450 MPa than those of the linear PBAs, whereas the elongations at break of the branched PBAs were in the range of 530–590%, which are much greater than the linear PBAs. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2143–2150, 2001
Electron spin resonance study on chemical‐crosslinking reaction mechanisms of polyethylene using a chemical agent. VI. Effect of α‐methyl styrene dimer
Authors: Yamazaki Takanori , Seguchi Tadao 
Published: October 2004

AbstractThe effect of α‐methyl styrene dimer (AMSD), which is used as a scorch retarder, on the reaction mechanisms of the chemical crosslinking of polyethylene (PE) with dicumyl peroxide (DCP) at high temperatures was investigated using electron spin resonance. When AMSD was added to PE containing DCP, the AMSD radical was observed; however, the PE alkyl radical or allyl radical presence was not detected. At 145 °C, crosslinking was obstructed as a result of the reaction between AMSD and alkyl radicals. As the temperature increased, AMSD fragmented to form 2‐phenyl‐2‐propyl and double bonds in PE. This generation of double bonds, however, accelerated crosslinking at 180 °C and was more effective than when AMSD was not present. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2151–2156, 2001
Effective grafting of polymers onto ultrafine silica surface: Photopolymerization of vinyl monomers initiated by the system consisting of trichloroacetyl groups on the surface and Mn2(CO)10
Authors: Shirai Yukio , Shirai Kumi , Tsubokawa Norio 
Published: October 2004

AbstractThe effective grafting of vinyl polymers onto an ultrafine silica surface was successfully achieved by the photopolymerization of vinyl monomers initiated by the system consisting of trichloroacetyl groups on the surface with Mn2(CO)10 under UV irradiation at 25 °C. The introduction of trichloroacetyl groups onto the surface of silica was achieved by the reaction of trichloroacetyl isocyanate with surface amino groups, which were introduced by the treatment of silica with 3‐aminopropyltriethoxysilane. During the polymerization, the corresponding polymers were effectively grafted onto the surface, based on the propagation of polymer from surface radicals formed by the interaction of trichloroacetyl groups and Mn2(CO)10. The percentage of poly(methyl methacrylate) grafting onto the silica reached 714.6% after 90 min. The grafting efficiency (proportion of grafted polymer to total polymer formed) in the polymerization of methyl methacrylate was very high, about 80%, indicating the depression of formation of ungrafted polymer. Polymer‐grafted silica gave a stable colloidal dispersion in good solvents for grafted polymer. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2157–2163, 2001
Phase‐equilibrium behavior of vinyl chloride/n‐butane and its application in determination of vinyl chloride heterogeneous polymerization kinetics
Authors: Bao Y. Z. , Brooks B. W. 
Published: October 2004

AbstractStudies of the phase‐equilibrium behavior of vinyl chloride (VCM)/n‐butane mixtures and the kinetics of VCM heterogeneous polymerization, using n‐butane as a reaction medium, were carried out using a 1‐L glass autoclave. The vapor composition was measured by gas chromatography, showing that the vapor pressure of the VCM/n‐butane mixture was located above the line connecting the points for pure VCM and n‐butane. The concentration of VCM in the vapor phase was greater than that in the corresponding liquid phase. It was confirmed that the presence of poly(vinyl chloride) (PVC) resin had no significant influences on the phase equilibrium of VCM/n‐butane mixtures. Thus, the phase‐equilibrium equations were applied to determine the conversion of VCM during heterogeneous polymerization. The conversions calculated from the variations of vapor pressure or composition agreed with those determined by the weighing method. The conversion–time and polymerization rate–time curves obtained for VCM heterogeneous polymerization showed that the polymerization accelerated at low initiator concentration, but the polymerization rate decreased with an increase of conversion at relatively high initiator concentrations. The chain‐transfer reaction to n‐butane was confirmed by a decrease of the molecular weight and broadening of the molecular weight distribution of PVC. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2179–2188, 2001
A facile approach to prepare soluble side‐chain polyimides for second‐order nonlinear optics
Authors: Sui Yu , Yin Jie , Hou Zhanjia , Zhu Na , Lu Jiongxin , Liu Yangang , Zhu Zikang , Wang Zongguang 
Published: October 2004

AbstractA simple and generally applicable new synthetic method to prepare second‐order nonlinear optical (NLO) polyimides has been developed. In this approach, side‐chain‐substituted polyimides were synthesized via isocyanato‐terminated prepolymers prepared directly from NLO chromophore‐containing diols Disperse Red 19. Using this technique, the tedious synthesis of the classical diamine monomers and harsh imidization process associated with polyamic acid prepolymers are avoided. The resulting polymers possessed good solubility and high glass‐transition (171–211 °C) and thermal‐decomposition temperatures. The polymers also exhibited excellent film‐forming properties, and good optical‐quality films were easily obtained by spin coating. The second‐order NLO activities of the polymer films were also studied, and several factors that might determine the growth of the second‐order NLO activity were proposed. The polymers obtained exhibit a large second‐order NLO activity (34–52.5 pm/V at 1064 nm). © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2189–2195, 2001
Radical heterogeneous polymerization behavior of N‐methyl‐α‐fluoroacrylamide in benzene
Authors: Sato Tsuneyuki , Maeda Yoshinori , Seno Makiko , Hirano Tomohiro 
Published: October 2004

AbstractThe polymerization of N‐methyl‐α‐fluoroacrylamide (NMFAm) initiated with dimethyl 2,2′‐azobisisobutyrate (MAIB) in benzene was studied kinetically and with electron spin resonance. The polymerization proceeded heterogeneously with the highly efficient formation of long‐lived poly(NMFAm) radicals. The overall activation energy of the polymerization was 111 kJ/mol. The polymerization rate (Rp) at 50 °C is given by Rp = k[MAIB]0.75±0.05 [NMFAm]0.44±0.05. The concentration of the long‐lived polymer radical increased linearly with time. The formation rate (Rp•) of the long‐lived polymer radical at 50 °C is expressed by Rp• = k[MAIB]1.0±0.1 [NMFAm]0±0.1. The overall activation energy of the long‐lived radical formation was 128 kJ/mol, which agreed with the energy of initiation (129 kJ/mol), which was separately estimated. A comparison of Rp• with the initiation rate led to the conclusion that 1‐methoxycarbonyl‐1‐methylethyl radicals (primary radicals from MAIB), escaping from the solvent cage, were quantitatively converted into the long‐lived poly(NMFAm) radicals. Thus, this polymerization involves completely unimolecular termination due to polymer radical occlusion. 1H NMR‐determined tacticities of resulting poly(NMFAm) were estimated to be rr = 0.34, mr = 0.48, and mm = 0.18. The copolymerization of NMFAm(M1) and St(M2) with MAIB at 50 °C in benzene gave monomer reactivity ratios of r1 = 0.61 and r2 = 1.79. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2196–2205, 2001