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991.
992.
基于Petri Net的需求流动网组建模型及其稳定性分析 总被引:1,自引:0,他引:1
针对供应链概念不足,提出需求流动网概念,并论述了需求流动网概念模型,运用Petri网理论建立需求流动网模型,并对模型进行了分析,随后在分析需求流动网稳定性内涵的基础上,进一步运用Petri网理论分析了需求流动网稳定性,并最终得出了相应结论. 相似文献
993.
H. Aoki S. Kosakabe M. Inumaru A. Kuboki S. Ohira M. Kodama 《Journal of Thermal Analysis and Calorimetry》2008,92(2):443-449
D-erythro sphingomyelines (SM) having a defined acyl chain were synthesized with sphingosylphosphorylcholine as a starting material,
and both a structural property and its relating phase transition phenomenon were compared between a symmetric chain length
SM (palmitoyl-SM: C16-SM) and asymmetric chain length SMs (behenoyl-SM: C22-SM, lignoceryl-SM: C24-SM). Furthermore, effect
of increasing a content of asymmetric chain SMs in the mixture systems of C22-SM/C16-SM, and C24-SM/C16-SM was investigated.
The present calorimetric and electron microscopic studies revealed that (1) The main transition enthalpy is smaller for the
asymmetric chain SMs than for the symmetric chain SM by about 3 kJ mol−1, although the acyl chain length is longer for the former than for latter; (2) Relatively small size vesicles (100∼200 nm
diameters) surrounded by one or more lamellae are observed for the asymmetric chain SMs, in contrast to large multilamellar
vesicles (1500∼2500 nm diameters) having at least fifteen stained lamellae for the symmetric chain SM and (3) The coexisting
asymmetric chain SMs cause the decrease in size and multiplicity for the MLV of the symmetric chain SM, simultaneously with
a decrease in the main transition enthalpy. 相似文献
994.
Andreas M. Nyström Jeremy W. Bartels Wenjun Du Karen L. Wooley 《Journal of polymer science. Part A, Polymer chemistry》2009,47(4):1023-1037
Reversible addition‐fragmentation chain transfer polymerization was employed to synthesize a set of copolymers of styrene (PS) and 2,3,4,5,6‐pentafluorostyrene (PPFS), as well as block copolymers with tert‐butyl acrylate (PtBA)‐b‐PS‐co‐PPFS, with control over molecular weight and polydispersity. It was found that the copolymerization of styrene and PFS allowed for the preparation of gradient copolymers with opposite levels of monomer consumption, depending on the feed ratio. Conversion to amphiphilic block copolymers, PAA‐b‐(PS‐co‐PPFS), by removing the protecting groups was followed by fitting with monomethoxy poly(ethylene glycol) chains. Solution‐state assembly and intramicellar crosslinking afforded shell crosslinked knedel‐like (SCK) block copolymer nanoparticles. These fluorinated nanoparticles (ca. 20 nm diameters) were studied as potential magnetic resonance imaging (MRI) contrast agents based on the 19F‐nuclei; however, it was found that packaging of the hydrophobic fluorinated polymers into the core domain restricted the mobility of the chains and prohibited 19F NMR spectroscopy when the particles were dispersed in water without an organic cosolvent. Packing of perflouro‐15‐crown‐5‐ether (PFCE) into the polymer micelle was demonstrated with good uptake efficiency; however, it was necessary to swell the core with a good solvent (DMSO) to increase the mobility and observe the 19F NMR signal of the PFCE. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1023–1037, 2009 相似文献
995.
本文研究一类具有特殊工件的平行机在线排序问题,目标是最小化最大完工时间.此模型有两种工件:正常工件和特殊工件.正常工件能够在m台平行机的任何一台机器上加工,而特殊工件仅能够在它唯一被指定的机器上加工.文中所有特殊工件的指定机器为M1.我们提供了竞争比为(2m2-2m 1)/(m2-m 1)的在线近似算法.当m=2时,算法是最好可能的.当m=3时,算法的竞争比为13/7≈1.857,并且提供了竞争比的下界(1 (平方根33))14≈1.686. 相似文献
996.
Recently, in the field of project scheduling problems the concept of partially renewable resources has been introduced. Theoretically, it is a generalization of both renewable and non-renewable resources. From an applied point of view, partially renewable resources allow us to model a large variety of situations that do not fit into classical models, but can be found in real problems in timetabling and labor scheduling. In this paper, we develop some preprocessing techniques and several heuristic algorithms for the problem. Preprocessing significantly reduces the dimension of the problems, therefore improving the efficiency of solution procedures. Heuristic algorithms based on GRASP and Path relinking are then developed and tested on existing test instances, obtaining excellent results. 相似文献
997.
研究了测度链上的柯西不等式,给出测度链上柯西不等式的具体形式.此外,还对测度链上的柯西不等式作了推广. 相似文献
998.
U. V. Manoj Jatinder N. D Gupta Sushil K. Gupta Chelliah Sriskandarajah 《Annals of Operations Research》2008,161(1):53-86
We study the benefits of coordinated decision making in a supply chain consisting of a manufacturer, a distributor, and several
retailers. The distributor bundles finished goods produced by the manufacturer and delivers them to the retailers to meet
their demands. The distributor is responsible for managing finished goods inventory. An optimal production schedule of the
manufacturer, if imposed on the distributor, may result in an increased inventory holding cost for the distributor. On the
other hand, an optimal distribution schedule of the distributor, if imposed on the manufacturer, may result in an increased
production cost for the manufacturer. In this paper we develop mathematical models for individual optimization goals of the
two partners and compare the results of these models with the results obtained for a joint optimization model at the system
level. We investigate the computational complexities of these scheduling problems. The experimental results indicate that
substantial cost savings can be achieved at the system level by joint optimization. We also study conflict and cooperation
issues in the supply chain. The cost of conflict of a supply chain partner is a measure of the amount by which the unconstrained
optimal cost increases when a decision is to be made under the scheduling constraint imposed by the other partner. We quantify
these conflicts and show that the cost of conflicts are significant. We also show that a cooperative decision will generate
a positive surplus in the system which can be shared by the two partners to make cooperation and coordination strategy more
attractive. 相似文献
999.
Elham Hosseini Nejad Patrice Castignolles Robert G. Gilbert Yohann Guillaneuf 《Journal of polymer science. Part A, Polymer chemistry》2008,46(6):2277-2289
Reversible addition fragmentation chain transfer (RAFT) was used to synthesize methacrylic acid oligomers and oligo(methacrylic acid)‐b‐poly(methyl methacrylate) (PMAA‐b‐PMMA) with targeted degree of polymerization ≈ 10. Characterization is by size‐exclusion chromatography (SEC) and electrospray mass‐spectrometry. SEC data are presented as hydrodynamic volume distributions (HVDs), the only proper means to present comparative and meaningful SEC data when there is no unique relationship between size and molecular weight. The RAFT agent, (4‐cyanopentanoic acid)‐4‐dithiobenzoate (CPADB), produced dithiobenzoic acid as a side product during the polymerization of methacrylate derivatives. Precipitation in diethyl ether proved to be an easy way to remove this impurity from the PMAA‐RAFT oligomers. Both unpurified and purified macro‐RAFT agent were used to prepare amphiphilic PMAA‐b‐PMMA copolymers. Diblock copolymer prepared from the purified PMAA homopolymer had a narrower HVD in comparison to those obtained from the equivalent unpurified macro‐RAFT agent. This work shows that while cyanoisopropyl‐dithiobenzoate or CPADB are good RAFT agents for methacrylate derivatives, they exhibit some instability under typical polymerization conditions, and thus when oligomers are targeted, optimal control requires checking for the degradation product and appropriate purification steps when necessary (the same effect is present for larger polymers but is unimportant). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2277–2289, 2008 相似文献
1000.
Dairen Lu Yun Wang Tianyuan Wu Kang Tao Lijia An Ruke Bai 《Journal of polymer science. Part A, Polymer chemistry》2008,46(17):5805-5815
Amphiphilic supramolecular miktoarm star copolymers linked by ionic bonds with controlled molecular weight and low polydispersity have been successfully synthesized via reversible addition‐fragmentation chain transfer (RAFT) polymerization using an ion‐bonded macromolecular RAFT agent (macro‐RAFT agent). Firstly, a new tetrafunctional initiator, dimethyl 4,6‐bis(bromomethyl)‐isophthalate, was synthesized and used as an initiator for atom transfer radical polymerization (ATRP) of styrene to form polystyrene (PSt) containing two ester groups at the middle of polymer chain. Then, the ester groups were converted into tertiary amino groups and the ion‐bonded supramolecular macro‐RAFT agent was obtained through the interaction between the tertiary amino group and 2‐dodecylsulfanylthiocarbonylsulfanyl‐2‐methyl propionic acid (DMP). Finally, ion‐bonded amphiphilic miktoarm star copolymer, (PSt)2‐poly(N‐isopropyl‐acrylamide)2, was prepared by RAFT polymerization of N‐isopropylacrylamide (NIPAM) in the presence of the supramolecular macro‐RAFT agent. The polymerization kinetics was investigated and the molecular weight and the architecture of the resulting star polymers were characterized by means of 1H‐NMR, FTIR, and GPC techniques. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5805–5815, 2008 相似文献