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排序方式: 共有6279条查询结果,搜索用时 0 毫秒
851.
OneClassofHyperbolicFunctionEquationand Its ApplicationBaiFengtu(白凤图)(NorthChinaInstituteofWaterConservancyandHydro-power)Abs... 相似文献
852.
选择Skyme势E作为两核子间唯象相互作用,在Hartree-Fock理论中结合粒子数守恒方法处理同类核子间的对相互作用,计算了Li和Be的丰中子同位素的结构,计算表明中子间的对相互作用和双中子晕之间存在紧密的联系. 相似文献
854.
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
855.
Hongwei Bai Yong Wang Li Liu Jihong Zhang Liang Han 《Journal of Polymer Science.Polymer Physics》2008,46(17):1853-1867
In this work, the nonisothermal crystallization and subsequent melting behaviors of polypropylene (PP) nucleated with different nucleating agents (NAs) have been studied. α‐phase NA 1,3:2,4‐bis (3,4‐dimethylbenzylidene) sorbitol (DMDBS, Millad 3988), β‐phase NA aryl amides compound (TMB‐5), and their compounds were introduced into PP matrix, respectively. The results show that the nonisothermal crystallization behaviors and crystalline structures of PP with compounded NAs are dependent on the composition of NAs. In the sample of PP with 0.1 wt % DMDBS and 0.1 wt % TMB‐5, the nucleation efficiency (NE) of TMB‐5 is much higher than that of DMDBS and PP crystallizes mainly nucleated by TMB‐5, and in this condition, β‐phase PP is the main crystallization structure. For the sample of PP with 0.2 wt % DMDBS and 0.2 wt % TMB‐5, 0.2 wt % DMDBS has higher NE than 0.2 wt % TMB5, and α‐phase is the main crystalline structure. The cooling rate is proved to be very important in controlling the nonisothermal crystallization behavior and the final crystalline structure of nucleated PP. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1853–1867, 2008 相似文献
856.
S. J. Bai 《Journal of Polymer Science.Polymer Physics》1994,32(16):2575-2583
High-temperature polymers were spum from liquid-crystalline solutions into fibers of superior thermal stability and mechanical properties. Fibers of two extended-chain polymers poly(p-phenyleneterephthalamide), PPTA, and poly-2,5-benzoxazole, ABPBO, as well as a rod-like polymer poly(p-phenylenebenzobisoxazole), PBO, were examined by axial x-ray scattering. Both wide-angle scattering and small-angle scattering were performed with CuKα radiation aiming along the fiber axis (c-axis) for structural information on the a-b lattice plane. In addition to previously reported lattice structure, the PPTA fibers (Kevlar® 29, 49, and 149) showed strong [004] and a [022] reflections suggesting that segments of the PPTA molecules were transverse to the fiber axis. This unique fiber structure is more prominent and the void content is less for the PPTA fibers with higher tensile modulus, (i.e., Kevlar® 149 > Kevlar® 49 > Kevlar® 29). Similar measurements on thermally annealed ABPBO and PBO fibers showed no [00l], [h0l], or [0kl] reflection indicative of a truly uniaxial molecular orientation. Evidence of microfibrillar order was discovered for the Kevlar® fibers and the ABPBO fiber. Results of conventional x-ray scattering on these fibers were compared and reconciled. © 1994 John Wiley & Sons, Inc. 相似文献
857.
Let {vij; i, J = 1, 2, …} be a family of i.i.d. random variables with E(v114) = ∞. For positive integers p, n with p = p(n) and p/n → y > 0 as n → ∞, let Mn = (1/n) Vn VnT , where Vn = (vij)1 ≤ i ≤ p, 1 ≤ j ≤ n, and let λmax(n) denote the largest eigenvalue of Mn. It is shown that
a.s. This result verifies the boundedness of E(v114) to be the weakest condition known to assure the almost sure convergence of λmax(n) for a class of sample covariance matrices. 相似文献
858.
The structures of the carbon sublayers in the annealed Co/C soft X-ray multilayers fabricated by using a dual-facing-target
sputtering system have been characterized by transmission electron microscopy (TEM) and Raman spectroscopy (RS). The results
suggest that the structural variations in the carbon layers can be roughly divided into three stages, i.e. ordering, crystalline
and grain growth stages. At the ordering stage with annealing temperatures below 400°C, the amorphous carbon layers change
from ones of bond-angle disorder and fourfold-bonding only to ones of threefold-bonding. At the crystalline stage, the amorphous
carbon layers in the as-deposited multilayers crystallize to graphite crystallites in the annealing temperature range of 500–600°C.
At the grain growth stage, the specimens are annealed at temperatures higher than 700°C. A growth in the graphite crystallite
dimensions is observed, which is consistent with the TEM results.
Project supported by the National Natural Science Foundation of China and Beijing Zhongguancun Associated Center of Analysis
and Measurement. 相似文献
859.
ACLASSOFFACTORIZATIONUPDATEALGORITHMFORSOLVINGSYSTEMSOFSPARSENONLINEAREQUATIONSBAIZHONGZHI(InstituteofComputationalMathematic... 相似文献
860.