排序方式: 共有199条查询结果,搜索用时 265 毫秒
191.
Anna Olszewska Paula Eronen Leena-Sisko Johansson Jani-Markus Malho Mikael Ankerfors Tom Lindström Janne Ruokolainen Janne Laine Monika Österberg 《Cellulose (London, England)》2011,18(5):1213-1226
This paper deals, with cationically modified NanoFibrillar Cellulose (cat NFC), obtained by reacting a dissolving pulp with
2,3-epoxypropyl trimethylammonium chloride (EPTMAC). The cat NFC was thoroughly characterized in terms of morphology and physical
properties. The dimensions of individual cellulose nanofibrils were determined by atomic force microscopy (AFM) imaging in
water and in air. Fibrils as thin as 0.8–1.2 nm were observed in water. The fibril diameter changed upon drying and the average
size was further quantified by image analysis. The experiments showed the importance of characterizing nanocellulosic materials
in situ before drying. The fibril size in air was confirmed by cryogenic transmission electron microscopy (cryo-TEM), and
it was found to be 2.6–3.0 nm. Smooth ultrathin films of cationic NFC were prepared by spincoating on silica substrates. The
effect of electrolyte concentration and pH on swelling of the cationic NFC film was studied using a quartz crystal microbalance
with dissipation. The results showed that at pH = 8 the cat NFC film was insensitive to electrolyte changes while at pH = 4.5,
the water content of the film decreased with increasing ionic strength. The electrophoretic mobility measurements showed a
cationic zeta potential for the cat NFC that decreased at increasing pH, verifying the swelling behaviour. 相似文献
192.
We study nongeneric planar trees and prove the existence of a Gibbs measure on infinite trees obtained as a weak limit of
the finite volume measures. It is shown that in the infinite volume limit there arises exactly one vertex of infinite degree
and the rest of the tree is distributed like a subcritical Galton-Watson tree with mean offspring probability m<1. We calculate the rate of divergence of the degree of the highest order vertex of finite trees in the thermodynamic limit
and show it goes like (1−m)N where N is the size of the tree. These trees have infinite spectral dimension with probability one but the spectral dimension calculated
from the ensemble average of the generating function for return probabilities is given by 2β−2 if the weight w
n
of a vertex of degree n is asymptotic to n
−β
. 相似文献
193.
The optimization of supply chain structures considering both economic and environmental performances is nowadays an important research topic. However, enterprises are commonly faced with the competing issues of reduced cost, improved customer service and increased environmental factors as a multi-faceted trade-off problem when designing supply chains. Hence, this paper proposes an environmentally conscious optimization model of a supply chain network with a broader and more comprehensive objective function that considers not just the transportation costs, but also the costs for the amount of greenhouse gas emissions, fuel consumption, transportation times, noise and road roughness. The paper sheds light on the trade-offs between various parameters such as vehicle speed, fuel, time, emissions, noise and their total cost, and offers managerial insights on economies of environmentally conscious supply chain optimization. An integer non-linear programming model is developed to help decision makers find the optimal solution under mentioned considerations. The proposed model is validated through the solution of an example, where its applicability to supply chain problems is demonstrated for managerial insights. 相似文献
194.
The splitting tendency of viscose and modal fibers in aqueous alkali solutions of LiOH, NaOH, KOH and TMAH was investigated.
The viscose fibers splitted up to 5–7 fibrils, whereas modal fibers splitted up to 2–4 fibrils depending on alkali type and
concentration. The fibrillar structure of lyocell enables it to split more (15–20 fibrils) than viscose and modal fibers.
Splitting occurs where internal stress of fiber is high due to different alkali or void distribution inside fiber. The splitting
test couldn’t be achieved for viscose and modal fibers between 1 and 5 M concentration of NaOH and TMAH solutions due to breakage
of fibers during test. Above 5 M concentration, no split can be observed due to even distribution of alkali inside fiber.
Paper presented at the 7th World Textile Conference, AUTEX 2007, Tampere, Finland, 26–28 June 2007.
Christian-Doppler Laboratory of Textile and Fiber Chemistry of Cellulosics is a Member of European Polysaccharide Network
of Excellence (EPNOE), www.epnoe.org 相似文献
195.
Using the relativistic Hartree-Fock (HFR) method developed by Cowan, we calculated the energy levels, Landé g-factors, and lifetimes for nd (n = 5–25), ns (n = 6–24), ng (n = 5–25), nf (n = 4–22), and np (n = 6–25) excited levels of doubly ionized lanthanum (La III, Z = 57). We compared the results with previously reported calculations
and experiments. 相似文献
196.
Pervin Deveci Bilge Taner Zafer Üstündağ Zeynel Kılıç Ali Osman Solak Emine Özcan 《Journal of Solid State Electrochemistry》2012,16(3):985-992
The modification of N-phenyl-aza-15-crown-5 (PA15C5) and N-(4-aminophenyl)-aza-15-crown-5 (4APA15C5) on glassy carbon (GC) electrode was performed by the electrochemical oxidation
of the corresponding azacrown derivatives in anhydrous acetonitrile media. The electrochemical behavior of the resulting modified
GC electrode was investigated in the presence of electroactive redox probes and these results, together with the X-ray photoelectron
spectroscopy (XPS) and reflection-absorption infrared spectroscopy were used to confirm the attachment of these molecules
onto the GC surface. The ellipsometric thicknesses of PA15C5 and 4APA15C5 films at the GC surface was obtained around 9.28 ± 0.40
and 10.50 ± 1.10 nm, respectively. Azacrown modified nanoscale surfaces serve as alkali metal sensor specific for their cavity
in the crown ring. 相似文献
197.
Beyhan Yiğit Murat Yiğit İsmail Özdemir Engin Çetinkaya 《Transition Metal Chemistry》2012,37(3):297-302
Three RuCl2(η6-arene, η1-carbene) and two RuCl2(NHC)(arene) complexes have been prepared by the reaction of bis(1,3-dialkylperhydrobenzimidazol-2-ylidene) (1) and bis(1,3-dialkyl-4-methylzimidazolin-2-ylidene) (3) with [RuCl2(arene)]2 in toluene and characterized by elemental analysis, 1H NMR, 13C NMR and IR spectroscopy. The catalytic activities of these complexes were examined in the transfer hydrogenation of aromatic
ketones using 2-propanol as hydrogen source. 相似文献
198.
We consider the optimal portfolio selection problem in a multiple period setting where the investor maximizes the expected
utility of the terminal wealth in a stochastic market. The utility function has an exponential structure and the market states
change according to a Markov chain. The states of the market describe the prevailing economic, financial, social and other
conditions that affect the deterministic and probabilistic parameters of the model. This includes the distributions of the
random asset returns as well as the utility function. The problem is solved using the dynamic programming approach to obtain
the optimal solution and an explicit characterization of the optimal policy. We also discuss the stochastic structure of the
wealth process under the optimal policy and determine various quantities of interest including its Fourier transform. The
exponential return-risk frontier of the terminal wealth is shown to have a linear form. Special cases of multivariate normal
and exponential returns are disussed together with a numerical illustration. 相似文献
199.
Abdullah Aydın Mehmet Akkurt Leyla Uzun Leyla Yıldırım Tijen Önkol 《Journal of chemical crystallography》2010,40(10):816-820