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181.
Oxidation of ethylene was carried out over alumina-supported metal oxide catalysts and highly dispersed gold catalysts, respectively, under atmospheric pressure. The ethylene was completely oxidized to produce carbon dioxide and water with both metal oxide and gold catalysts. The activity of gold catalyst prepared by deposition method was much higher than that of supported metal oxide catalysts. Ultra-fine gold particles on Co3O4 were more active than on Al2O3. Fe2O3/Al2O3 and MnO2/Al2O3 catalysts were more active than MoO3/Al2O3 catalyst. The activity of the supported metal oxide catalysts was greatly enhanced by addition of gold particles. It was therefore considered that gold particles promote dissociative adsorption of oxygen and the adsorbed oxygen reacts with adsorbed ethylene on support adjacent to the active site. 相似文献
182.
In the paper, we present an interactive decision procedure for aggregating group members’ preferences which are specified in incomplete ways. A group consensus under incomplete information is not usually reached at a single step since less-specific preferences on attribute weights and performance scores make a clear selection of best alternative more difficult. To circumvent these difficulties, a measure, indicating the strength of preference between alternatives, is derived to help each of decision makers change his/her preference structure. To make preference changes based on the measure effective, we present a solution method to convert an intractable nonlinear programme into a linear one. 相似文献
183.
For small Hamiltonian perturbation of a Hamiltonian systemof arbitrary number of degrees of freedom with anormally non-degenerate submanifold of periodic orbits we construct a nearbysubmanifold and an `effective Hamiltonian' on it such that the differencebetween the two Hamiltonian vector fields is small. The effective Hamiltonianis independent of one coordinate, the `overall phase', and hence thecorresponding action is preserved. Unlike standard averaging approaches,critical points of our effective Hamiltonian subject to given actioncorrespond to exact periodic solutions. We prove there has to be at least acertain number of these critical points given by global topological principles.The linearisation of the effective Hamiltonian about critical points is provedto give the linearised dynamics for the full system to leading order in theperturbation. Hence in the case of distinct eigenvalues which move at non-zerospeed with ,the linear stability type of the periodic orbit can be read offfrom the effective Hamiltonian. Our principal application is to networks ofoscillators or rotors where many such submanifolds of periodic orbits occurat the uncoupled limit – simply excite a number N 2 of the units inrational frequency ratio and put the others on equilibria, subject to anon-resonance condition. The resulting exact periodic solutions for weakcoupling are known as multibreathers. We call the approximate solutions givenby the effective Hamiltonian dynamics, `generalised multibreathers'. Theycorrespond to solutions which look periodic on a short time scale but therelative phases of the excited units may evolve slowly. Extensions aresketched to travelling breathers and energy exchange between degrees offreedom. 相似文献
184.
Ki Byung Sunwoo Seung Joon Park Seong Jae Lee Kyung Hyun Ahn Seung Jong Lee 《Rheologica Acta》2002,41(1-2):144-153
Three-dimensional numerical simulation of viscoelastic coextrusion process has been performed and numerical results were
compared with the experimental data of Karagiannis et al. (1990). By varying the magnitude of the second normal stress difference
and its ratio of Fluid I and Fluid II, we were able to control the interface profile and the degree of encapsulation along
the downstream direction. By increasing the parameter α (αFluid I=αFluid II) from 0.1 to 0.4 in the Giesekus model and increasing the α ratio (αFluid IαFluid II) between Fluid I and Fluid II from 2.0 to 4.0 in the permissible range of realistic polymeric systems, the interface profile
and the degree of encapsulation along the downstream direction were fitted with the experimental results. There was little
difference between the numerical results and the experimental data in the interface profile and the degree of encapsulation
along the downstream direction when the α ratio was set to 3.0 (0.3:0.1). Fluid I with larger magnitude of the second normal
stress difference protrudes into Fluid II with smaller magnitude of the second normal stress difference around the symmetric
plane, while Fluid II wraps around Fluid I near the side walls. As the ξ
1
ratio (ξ
1
,Fluid Iξ
1
,Fluid II) increases from 1.0 to 3.0 for the two-mode Phan-Thien and Tanner model, it was found that the curvature of the interface
profile increased, and the difference between the numerical results and the experimental data in the interface profile and
the degree of encapsulation along the downstream direction was almost negligible when the ξ
1
ratio was set to 3.0 (0.54:0.18). Although the parameters of viscoelastic models were fitted by using the shear viscosity
data only, quantitative agreements between the numerical results and the experimental coextrusion data were quite satisfactory.
Received: 24 April 2001 Accepted: 5 June 2001 相似文献
185.
We investigate the rheological behavior of the polymer blends with fibril morphology, with special focus on the effect of fibril morphology on the extensional properties under uniaxial extension. We add a small amount of the dispersed phase to the matrix, and control the blend morphology by changing the viscosity ratio. When the fibril morphology is maintained, the blend shows not only a significant increase of the extensional viscosity but the strain hardening behavior. The extensional viscosity increases depending on the aspect ratio of the fibers, while the strain hardening behavior originates from the restricted stretching of deformable fibers, which has been confirmed theoretically by introducing the concept of rigidity of the fiber. It suggests a way to induce the strain hardening behavior by introducing deformable fibrils into the matrix, that is, by the design of polymer blends with a small amount of dispersed phase such that the fibril structure is maintained. 相似文献
186.
Byeong Seok Ahn 《The Journal of the Operational Research Society》2017,68(11):1307-1311
This paper considers ranked voting systems to determine the rank order of candidates who compete for a limited number of positions. We show that the preferential voting problems based on the data envelopment analysis (DEA) (Wang et al, 2007) can be solved using the extreme points of constraints on rank position importance incorporated in the formulation. This is basically due to the fact that the so-called inverse positive property of the constraints makes it possible to easily find their extreme points. Further, we emphasize that this finding is not restricted to Wang et al’s two linear models, but is also applicable to other DEA-based preferential voting problems, which include the constraints accounting for different relative gaps between rank positions. 相似文献
187.
Kyu Hyun Jung Gun Nam Manfred Wilhellm Kyung Hyun Ahn Seung Jong Lee 《Rheologica Acta》2006,45(3):239-249
Rheological properties of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer
solution in both linear and nonlinear regions have been investigated. PEO-PPO-PEO triblock copolymer solution shows a dramatic
change in mechanical properties as temperature changes. PEO-PPO-PEO triblock copolymer undergoes a transition from sol to
gel with increase of temperature. During this transition the copolymer solution passes through three different stages, namely
sol, soft gel, and hard gel. In our previous research (Hyun et al. in J Non-Newtonian Fluid Mech 55:51–65, 2002), large amplitude oscillatory shear (LAOS) behavior was found to be very sensitive to the generated microstructures. In this
study, we investigated the relationship between the LAOS type and the microdomain structure. Newtonian behavior is observed
in sol region, while there appear two kinds of LAOS types in the soft gel region. One is type I (G′, G′′ decreasing) and the other is a combination of type I and type IV (G′, G′′ increasing followed by decreasing). Type III (G′ decreasing, G′′ increasing followed by decreasing) is observed in the hard gel region. We compared the shape of stress curves, Lissajous
pattern, and Fourier transform (FT) rheology of hard gel and soft gel under LAOS, and tried to relate the complex LAOS behavior
with the microstructural change. From these investigations, it was found that the LAOS behavior and the stress pattern at
large strain are closely related to the microdomain structure of PEO-PPO-PEO triblock copolymer, and provide a lot of useful
information on the microstructures induced by large deformation. 相似文献
188.
The efficacy of photodynamic therapy (PDT) depends upon the amount of photosensitizer accumulated in the malignant tissues. Radachlorin is a popular photosensitizer used in photodynamic therapy to treat various types of cancer. In this study, we have studied the main organelles responsible for the accumulation of radachlorin in human anaplastic thyroid cancer in vitro and in vivo. The optimal time window for uptake and clearance of radachlorin also was studied. Confocal microscopic images confirmed that the radachlorin is mainly acquired by mitochondria and partially by lysosome and endoplasmic reticulum. Studies also showed that the maximum amount of radachlorin was accumulated within 3–6 h after the treatment. Radachlorin also showed a higher affinity toward malignant tumors compared to the other organs in mice xenograft model. Uptake of radachlorin reached an optimum amount within 6 h and most of the radachlorins were also cleared from the body in next 48 h. Therefore, detailed information regarding exact accumulation sites and a time window in which maximum amount of drug is accumulated and cleared were obtained by this study. Hence, not only the efficacy of the treatment can be increased but the phototoxicity after the treatment also can be controlled. 相似文献
189.
The results of and findings from an interlaboratory comparison among laboratories carrying out food testing of pesticide residues
in the APEC (Asia–Pacific Economic Cooperation) region are presented and discussed to show critical roles of chemical metrology
infrastructure in establishing traceability of measurements and in supporting existing measurement capability in safety and
quality of food trade. The study material, which was prepared and certified by Korea Research Institute of Standards and Science
(KRISS), was freeze-dried Chinese cabbage powder fortified with two organophosphorous pesticides (diazinon and chlorpyrifos).
Among 14 participants, 12 laboratories were accredited based on ISO/IEC17025 and one laboratory was under assessment for the
accreditation at the time of this study. Though all participants demonstrated very good intra-day repeatability and inter-day
intermediate precision, many of them showed a large bias from the certified values. It is suggested that in addition to the
accreditation system, economies are encouraged to develop appropriate chemical metrology infrastructure, which could effectively
support laboratories to assure measurement traceability to SI, for which NMIs could play significant roles through their metrological
services recognized in Mutual Recognition Arrangement (MRA) of the International Committee for Weights and Measures (Comité
International des Poids et Mesures, CIPM). 相似文献
190.
Peterca M Imam MR Ahn CH Balagurusamy VS Wilson DA Rosen BM Percec V 《Journal of the American Chemical Society》2011,133(7):2311-2328
The synthesis, structural, and retrostructural analysis of two libraries containing 16 first and second generation C(3)-symmetric self-assembling dendrimers based on dendrons connected at their apex via trisesters and trisamides of 1,3,5-benzenetricarboxylic acid is reported. A combination of X-ray diffraction and CD/UV analysis methods demonstrated that their C(3)-symmetry modulates different degrees of packing on the periphery of supramolecular structures that are responsible for the formation of chiral helical supramolecular columns and spheres self-organizable in a diversity of three-dimensional (3D) columnar, tetragonal, and cubic lattices. Two of these periodic arrays, a 3D columnar hexagonal superlattice and a 3D columnar simple orthorhombic chiral lattice with P222(1) symmetry, are unprecedented for supramolecular dendrimers. A thermal-reversible inversion of chirality was discovered in helical supramolecular columns. This inversion is induced, on heating, by the change in symmetry from a 3D columnar simple orthorhombic chiral lattice to a 3D columnar hexagonal array and, on cooling, by the change in symmetry from a 2D hexagonal to a 2D centered rectangular lattice, both exhibiting intracolumnar order. A first-order transition from coupled columns with long helical pitch, to weakly or uncorrelated columns with short helical pitch that generates a molecular rotator, was also discovered. The torsion angles of the molecular rotator are proportional to the change in temperature, and this effect is amplified in the case of the C(3)-symmetric trisamide supramolecular dendrimers forming H-bonds along their column. The structural changes reported here can be used to design complex functions based on helical supramolecular dendrimers with different degree of packing on their periphery. 相似文献