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The phase behavior and volumetric properties of polyethylene (PE) in solutions of n‐pentane and n‐pentane/CO2 were studied in a temperature (T) range of 370–440 K at pressures up to 60 MPa. Measurements were conducted with a variable‐volume view‐cell system equipped with optical sensors to monitor the changes in the transmitted light intensity as the P or the T of the system was changed. Lower‐critical‐solution‐temperature‐type behavior was observed for all of the liquid–liquid (L–L) phase boundaries, which shifted to higher pressures in solutions containing CO2. The solid–fluid (S–F) phase boundaries were investigated over a P range of 8–54 MPa and took place in a narrow T range, from 374 to 378 K in this P interval. The S–F phase boundary showed a unique feature in that the demixing temperatures showed both increasing and decreasing trends with P depending on the P range. This was observed in both the PE/n‐pentane and PE/n‐pentane/CO2 mixtures. The density of these solutions were measured as a function of P at selected temperatures or as a function of T at selected pressures that corresponded to the paths followed in approaching the phase boundaries (S–F or L–L) starting from a homogeneous one‐phase condition. The data showed a smooth variation of the overall mixture density along these paths. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2201–2209, 2003 相似文献
4.
Effects of storage period on hydroxymethylfurfural, pH and colour were studied in white hard grape pekmez (Zile pekmezi), a Turkish traditional product. Pekmez samples were stored at 20 °C for 8 months. Analysis of variance revealed significant differences in hydroxymethylfurfural, pH, L, a and b values (P<0.01) based on storage time. 相似文献
5.
Reset controllers are linear controllers that reset some of their states to zero when their input is zero. We are interested in their feedback connection with linear plants, and in this paper we establish fundamental closed-loop properties including stability and asymptotic tracking. This paper considers more general reset structures than previously considered, allowing for higher-order controllers and partial-state resetting. It gives a testable necessary and sufficient condition for quadratic stability and links it to both uniform bounded-input bounded-state stability and steady-state performance. Unlike previous related research, which includes the study of impulsive differential equations, our stability results require no assumptions on the evolution of reset times. 相似文献
6.
Orhan Gazi A. Ozgur Yilmaz 《Communications Letters, IEEE》2007,11(2):173-175
Decoding delay is an important consideration for the use of turbo codes in practical applications. We propose a new structure for turbo codes which is very suitable for parallel decoding. It is shown by union bound analysis and simulation results that the proposed system performance is comparable to that of the classical turbo codes 相似文献
7.
Ayhan Demirbas M. Masuk Kü ü k Yunus Erdogan M. Ya in Nutku Oktay Torul 《Petroleum Science and Technology》1992,10(2):185-197
A kinetic study of pyrolysis of dried black liquor was performed using a Netzsch 429 Thermogravimetric Analyzer. It was found that as conversion increases from 10 to 45% the apparent pyrolysis activation energy for black liquor increases from 77.20 to 112.74 KJ/mol. For black liquor the order of reaction was found to be first-order. The reaction rate constant was found to be 2.12×109 min. These results are in agreement with the data reported by other investigators on biomass pyrolysis. 相似文献
8.
Erdogan Kiran 《Polymer》2008,49(7):1853-1859
Morphological changes that take place in poly(?-caprolactone) upon exposure to carbon dioxide at high pressures have been explored as a function of pressure and temperature. SEM and DSC results point to a competition between CO2-modulated crystallization and pressure-induced phase separation which leads to unique morphologies. At 293 K, exposure to CO2 at pressures up to 45 MPa leads to recrystallization resulting in higher level of crystallinity and higher melting temperatures. Highest crystallinity levels along with distinct crystal morphology were observed after exposure to CO2 at 308 K and 21 MPa. At a higher pressure at this temperature (308 K/34 MPa) polymer undergoes melting, and foaming is achieved during depressurization prior to solidification. At 323 K, the polymer is found to display unique crystal morphology with concave crystal geometry as well as porous domains. The results are discussed in terms of the crystallization and phase separation paths that are followed during exposure to CO2 and the depressurization stages. 相似文献
9.
Using genetic algorithm for the optimization of seismic behavior of steel planar frames with semi-rigid connections 总被引:1,自引:0,他引:1
Asghar?Vatani?OskoueiEmail author Sahand?Sarioletlagh?Fard Orhan?Aksogan 《Structural and Multidisciplinary Optimization》2012,45(2):287-302
Beam-column connections have a significant role in the results of the analysis and the design of steel frames. In this paper,
a genetic algorithm has been used for the non-linear analysis and design of steel frames. For minimizing the weight of frames,
while satisfying the applied constraints and restraints such as the limits of normal and combined stresses, criteria such
as target displacement(s) and the number and locations of plastic hinges were used. To analyze and design the frame elements,
I and box-shaped standard sections were used for beams and columns, respectively. Finally, some clues for finding optimizing
semi-rigid connection stiffness values for beam-to-column connections have been obtained. The degrees of these rigidities
are obtained by a genetic algorithm during the procedure of optimization in order to reach a frame with the minimum weight.
SAP2000 structural analysis program was used to perform modal analysis and linear and non-linear static solutions as well
as the design of the elements. A MATLAB program was written for the process of optimization. The procedure of optimization
was based on a weight minimization carried out for 9 steel frames. Thus, the optimum connection stiffness could be obtained
for minimizing the weight of the structure. The results show that the non-linear analysis gives less weight for short period
frames with semi-rigid connections compared to those of linear ones. However, by increasing the periods of frames, much less
weights are obtained in the case of non-linear analysis with semi-rigid connections. 相似文献
10.
The high pressure solubility of polyethylene standards (Mw = 2100, 16400, 108000 and 420000 and Mw/Mn = 1.14, 1.16, 1.32 and 2.66, respectively) in n-pentane has been studied. Concentrations of up to 15 wt% polymer have been investigated. For each polymer sample and concentration, pressures that are required to achieve single-phase solutions have been determined over a range of temperatures. The solutions are found to all show lower critical solution temperatures. Demixing pressures are observed to depend strongly on the molecular weight of the polymer. 相似文献