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991.
Klaus Dieter Schwenke Andreas Dahme Thomas Wolter 《Journal of the American Oil Chemists' Society》1998,75(1):83-87
The gel-forming abilities of a rapeseed protein isolate, composed of 70% globulin (cruciferin) and 30% albumin (napin), and
their individual protein components, were investigated. The influence of acetylation upon the gelation properties was also
studied. Highest gel strength (measured as shear modulus) of the isolate was obtained at pH values around 9, which is between
the isoelectric points of both major proteins. Purified cruciferin gave the highest shear modulus values, with maxima at pH
6 and 8. Weak and poorly stable gels exhibiting strong hysteresis were obtained with isolated napin. Acetylation resulted
in a pH shift of the shear modulus maximum of the protein isolate to about 6. The gelation temperature of the acetylated isolate
had the highest pH and concentration dependence compared with the other proteins. 相似文献
992.
Norbert Moszner Frank Zeuner Thomas Vlkel Urs Karl Fischer Volker Rheinberger 《应用聚合物科学杂志》1999,72(13):1775-1782
1,3‐Bis[(1‐alkoxycarbonyl‐2‐vinylcyclopropane‐1‐yl)carboxy]benzenes 1 [RO: CH3O (a), C2H5O (b)] were synthesized by the esterification of the corresponding 1‐alkoxycarbonyl‐2‐vinylcyclopropane‐1‐carboxylic acids with resorcinol. The structure of the new vinylcyclopropanes was confirmed by elemental analysis and infrared (IR), 1H nuclear magnetic resonance (1H‐NMR), and 13C nuclear magnetic resonance (13C‐NMR) spectroscopy. The radical polymerization of difunctional 2‐vinyl‐cyclopropanes in bulk with 2,2′‐azoisobutyronitrile (AIBN) results in hard, transparent, crosslinked polymers. During the bulk polymerization of the crystalline bis[(1‐methoxycarbonyl‐2‐vinylcyclopropane‐1‐yl)carboxy]benzene 1a, an expansion in volume of about 1% took place. The radical solution polymerization of 1a resulted in a soluble polymer with pendant 2‐vinylcyclopropane groups. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1775–1782, 1999 相似文献
993.
A block copolymer nanotemplate for mechanically tunable polarized emission from a conjugated polymer
A polymer blend system consisting of polystyrene grafted onto poly (p-phenylene ethynylene) (PS-g-PPE) and poly (styrene-block-isoprene-block-styrene) triblock copolymer (SIS) yields highly polarized emission due to the unidirectional alignment of the PPE molecules. During the roll casting, the triblock copolymer microphase separates and creates unidirectionally aligned PS cylindrical microdomains in the rubbery PI matrix. PPE, a fluorescent conjugated polymer, was grafted with polystyrene (PS) side chains that enabled sequestration and alignment of these rigid backbone emitter molecules into the PS microdomains of the SIS triblock copolymer. Deforming the thermoplastic elastomer in a direction perpendicular to the orientation direction of the cylinders causes rotation of the PS cylinders and the PPE emitter molecules and affords tunable polarized emission due to re-orientation of the PPE containing PS cylinders as well as film thinning from Poisson effect. 相似文献
994.
The gas permeability coefficient of nano and micro composites of natural rubber, carboxylated styrene butadiene rubber and 70:30 natural rubber/carboxylated styrene butadiene rubber blend membranes has been investigated with special reference to type of filler, gases, filler loading and pressure. The layered silicates such as sodium bentonite and sodium fluorohectorite were the nanofillers used and the conventional micro fillers were clay and silica. Latex nanocomposites were characterized by X-ray diffraction technique. The dispersion of layered silicates in the polymer matrix was analysed using transmission electron microscopy. The fluorohectorite silicate showed excellent dispersion in natural rubber matrix. The effect of free volume on the gas barrier properties was investigated by positron annihilation lifetime spectroscopy. It was observed that due to the platelet like morphology and high aspect ratio of layered silicates, the gas barrier properties of nano filled latex membranes were very high. The crosslink density values and extent of reinforcement were estimated in order to correlate with the gas barrier properties. The oxygen/nitrogen selectivity of these membranes were investigated. The diffusion of gas molecules through the polymer was determined by time-lag method and diffusion selectivity of the membranes was computed. 相似文献
995.
Do-Kyun Kwon Clive A. Randall Thomas R. Shrout Michael T. Lanagan 《Journal of the American Ceramic Society》2004,87(6):1088-1092
The dielectric properties and frequency dispersion associated with a dielectric relaxation were evaluated within the perovskite (1− x )BiScO3 – x Ba(Mg1/3 Nb2/3 )O3 solid solution systems (0.7 ≤ x ≤ 1). With increasing BiScO3 , the room-temperature dielectric permittivity at low frequency (100 Hz) increased up to 115 at x = 0.7, and a dielectric relaxation phenomenon was evident. Relaxation parameters were analyzed using several Arrhenius-type equations, and the microwave dielectric property measurement using rectangular wave-guide method enabled confirmation of the extrapolated value of the Arrhenius plot. The result of the microwave dielectric property measurement was also checked with J -function fitting based on the frequency-dependent Gaussian distribution of the associated dielectric loss data at low frequency. 相似文献
996.
Chungen Yin Lasse Rosendahl Søren K. Kær Thomas J. Condra 《Chemical engineering science》2004,59(16):3281-3292
Co-firing biomass with coal or gas in the existing units has gained increasing interest in the recent past to increase the production of environmentally friendly, renewable green power. This paper presents design considerations for co-firing biomass with natural gas in wall-fired burners by use of numerical modeling. The models currently used to predict solid fuel combustion rely on a spherical particle shape assumption, which may deviate a lot from reality for big biomass particles. A sphere gives a minimum in terms of the surface-area-to-volume ratio, which impacts significantly both motion and reaction of a particle. To better understand the biomass combustion and thus improve the design for co-firing biomass in wall-fired burners, non-sphericity of biomass particles is considered. To ease comparison, two cases are numerically studied in a long gas/biomass co-fired burner model. (1) The biomass particles are assumed as solid or hollow cylinders in shape, depending on the particle group. To model accurately the motion of biomass particles, the forces that could be important are all considered in the particle force balance, which includes a drag for non-spherical particles, an additional lift due to particle non-sphericity, and a “virtual-mass” force due to relatively light biomass particles, as well as gravity and a pressure-gradient force. Since the drag and lift forces are both shape factor- and orientation-dependent, coupled particle rotation equations are resolved to update particle orientation. To better model the reaction of biomass particles, the actual particle surface area available and the average oxygen mass flux at particle surface are considered, both of which are shape factor-dependent. (2) The non-spherical biomass particles are simplified as equal-volume spheres, without any modification to the motion and reaction due to their non-sphericity. The simulation results show a big difference between the two cases and indicate it is very significant to take into account the non-sphericity of biomass particles in order to model biomass combustion more accurately. Methods to improve the design for co-firing biomass in wall-fired burners are finally suggested. 相似文献
997.
Kerim Isik Gregory Gerstein Thomas Schneider Robert Schulte Daniel Rosenbusch Till Clausmeyer Florian Nürnberger Milan Vucetic Sergej Koch Sven Hübner Bernd-Arno Behrens A. Erman Tekkaya Marion Merklein 《Production Engineering》2016,10(1):5-15
Sheet-bulk metal forming processes combine conventional sheet forming processes with bulk forming of sheet semi-finished parts. In these processes the sheets undergo complex forming histories. Due to in- and out-of-plane material flow and large accumulated plastic strains, the conventional failure prediction methods for sheet metal forming such as forming limit curve fall short. As a remedy, damage models can be applied to model damage evolution during those processes. In this study, damage evolution during the production of two different toothed components from DC04 steel is investigated. In both setups, a deep drawn cup is upset to form a circumferential gearing. However, the two final products have different dimensions and forming histories. Due to combined deep drawing and upsetting processes, the material flow on the cup walls is three-dimensional and non-proportional. In this study, the numerical and experimental investigations for those parts are presented and compared. Damage evolution in the process chains is simulated with a Lemaitre damage criterion. Microstructural analysis by scanning electron microscopy is performed in the regions with high mechanical loading. It is observed that the evolution of voids in terms of void volume fraction is strongly dependent on the deformation path. The comparison of simulation results with microstructural data shows that the void volume fraction decreases in the upsetting stage after an initial increase in the drawing stage. Moreover, the concurrent numerical and microstructural analysis provides evidence that the void volume fraction decreases during compression in sheet-bulk metal forming. 相似文献
998.
Philipp Landkammer Thomas Schneider Robert Schulte Paul Steinmann Marion Merklein 《Production Engineering》2016,10(1):93-102
Inverse form finding aims in determining the optimal material configuration of a workpiece for a specific forming process. A gradient- and parameter-free (nodal-based) form finding approach has recently been developed, which can be coupled non-invasively as a black box to arbitrary finite element software. Additionally the algorithm is independent from the constitutive behavior. Consequently, the user has not to struggle with the underlying optimization theory behind. Benchmark tests showed already that the approach works robustly and efficiently. This contribution demonstrates that the optimization algorithm is also applicable to more sophisticated forming processes including orthotropic large strain plasticity, combined hardening and frictional contact. A cup deep drawing process with solid-shell elements and a combined deep drawing and upsetting process to form a functional component with external teeth are investigated. 相似文献
999.
Thomas J. Siller Alma Rosales John Haines Aaron Benally 《Canadian Metallurgical Quarterly》2009,135(3):102-108
The development of engineering students’ professional skills has gained considerable national attention from Accreditation Board for Engineering and Technology, the National Academy of Engineering, ASCE, and other constituents. There is little debate that these professional skills are necessary. Engineering programs have tried many approaches to develop these skills in the undergraduate programs. Colorado State University (CSU) has developed a new approach modeled on the type of professional development that occurs in the professional environment. This new Professional Learning Institute (PLI) provides students with a broad array of workshops, presentations, and experiential opportunities addressing the areas of cross cultural communication and teamwork, innovation, leadership, ethics, and public service. This program introduces students to the concept of professional development through required extracurricular activities, includes minimum requirements along with requirements to earn certificates in specialty areas for motivated students. The majority of offerings in the PLI are presented by leaders from the engineering profession who have teamed with CSU to provide high quality programs for our students. 相似文献
1000.
F.J. Berry I.S. Lyubutin E.A. Moore M.F. Thomas T.V. Dmitrieva 《Materials Chemistry and Physics》2009,113(2-3):714-716
The tin-doped sulphur-containing compound of composition Fe1.05Cr1.90Sn0.05S4, in which tin is located on the octahedral sites as Sn(IV) in the spinel-related structure, has been examined by 119Sn Mössbauer spectroscopy. The data complement results obtained by 57Fe Mössbauer spectroscopy and show that tin doping increases the magnetic ordering temperature of pure FeCr2S4. These results are compared with the data obtained on tin-doped CuCr2X4 compounds (X = O, S, Se). 相似文献