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161.
Wan Y. Shih Wei-Heng Shih Ilhan A. Aksay 《Journal of the American Ceramic Society》1997,80(5):1073-1078
We have examined the axial displacement, Δ h , and maximum axial pressure, P max , of flextensional transducers such as the moonies and the rainbows with both scaling and mechanical analyses. For a constant electric field E across the transducer, Δ h / t ∝ E / t 2 where t is the thickness of the rainbow or the thickness of the metal end cap of the moonie and Δ h / t , the relative axial displacement. Thus, for a constant voltage V across the transducer, Δ h / t ∝ V / t 3 . As for the maximum pressure, P max t 2 for the rainbows and P max ∝ wt for the moonies where t is the thickness of the rainbow or the thickness of the metal end cap of the moonie and w the thickness of the piezoelectric disk of the moonie. These predictions agree well with the experimental results found in the rainbows and the moonies. Our analysis showed that although the rainbows and the moonies differ in design and processing, the underlying physics for the enhancement in the axial displacement are essentially the same: The nonuniform distribution of d 31 through the thickness of the transducer causes the transducer to arch or flatten with an applied electrical field, which leads to the enhancement in the axial displacement. The only difference is that, for the transducer to arch, the applied field is in the opposite direction to the polarization in the rainbows but in the same direction as the polarization in the moonies. 相似文献
162.
163.
Temperature-dependent diffusion coefficient of soluble substances during ethanol extraction of clove
San Myint Wan Ramli Wan Daud Abu Bakar Mohamad Abdul Amir H. Kadhum 《Journal of the American Oil Chemists' Society》1996,73(5):603-610
The temperature dependence of the diffusion coefficient of ethanol-soluble substances from ground cloves (particle size 250
μm) during extraction was estimated by fitting batch extraction data at several temperatures (27.8, 40, 50, and 60°C) to a
previously developed mass transfer model. The model was based on spherical geometry of particles. Nonlinear regression analysis
was used to develop an equation that describes the diffusivity as a function of temperature. The temperature dependence ofD
A
was of the Arrhenius type. 相似文献
164.
Wan Ramli Wan Daud 《应用聚合物科学杂志》1986,31(8):2457-2465
The calendering of non-Newtonian fluids by two rotating cylinders to produce thin films of fluids finds wide application in polymer sheet-making and food-drying industries. Theoretical work has previouly been devoted to the symmetrical case where the cylinders are of equal diameters rotating at the same speed. The present work proposes a new one-film theory of calendering of power law fluids for unequal radii and surface velocities of the calendering cylinders. The relationship between the dimensionless thickness of the calendered fluid, Δe* and that of the incoming fluid, Δi* is shown to be a function of the ratio of the surface velocities of the cylinders and the power law index. The result further shows that Δe* tends to asymptote after the second decade of Δi* 相似文献
165.
166.
P. J. Wan R. J. Hron Sr. M. K. Dowd M. S. Kuk E. J. Conkerton 《Journal of the American Oil Chemists' Society》1995,72(6):661-664
Hexane has been used for decades to extract oil from cottonseed and is still the solvent of choice for the edible-oil industry.
Due to increased regulations as a result of the 1990 Clean Air Act and potential health risks, the edible-oil extraction industry
urgently needs an alternate hydrocarbon solvent to replace hexane. Based on laboratory-scale extraction tests, two hydrocarbon
solvents, heptane and isohexane, were recommended as potential replacements for hexane. A cottonseed processing mill with
a 270 MT/day (300 tons/day) capacity agreed to test both solvents with their expander-solvent process. Extraction efficiencies
of isohexane and heptane, judged by extraction time and residual oil in meal, refined and bleached color of miscella refined
oil, and solvent loss, were comparable to that of hexane. However, fewer problems were encountered with the lower-boiling
isohexane than with the higher-boiling heptane. With isohexane, the daily throughput increased more than 20%, and natural
gas consumption decreased more than 40% as compared to hexane. 相似文献
167.
针对国产的硫酸生产用钒催化剂普遍存在的反应活性欠稳定、颗粒强度偏低、催化剂床层阻力偏大等问题,采取了对载体硅藻土进行共再浆水选处理、煅烧处理、热浓硫酸处理;晨添加剂中加入稀有元素,提高钾钒比,优化中和条件;采用专利技术成型,成品采用立式煅烧等技术措施,提高了钒催化剂的性能。改进后的钒催化剂不易粉化,低温型钒催化剂的活性明显提高,起燃温度可降至350℃,390℃以下的活性明显优于宽温型的,宽温型钒催化剂在390-450℃的活性更为优异。 相似文献
168.
Pt, Ir, Pt-Ir and Pt-Ni bimetallic catalysts supported on NaY- and HY-zeolite were examined as a catalyst for producing gasoline
from n-decane via simultaneous reforming and cracking. The catalysts were prepared by calcining and reducing metal-ion-exchanged
Y-zeolite with O2 and H2 at 300°C., respectively. Thus prepared catalysts were characterized by hydrogen chemisorption and temperature programmed
desorption of ammonia. Pt-Ni/NaY and Pt-Ir/NaY bimetallic catalysts offered the improved activity maintenance compared to
Pt/NaY monometallic catalyst. The catalysts supported on HY-zeolite showed higher selectivity toward C5–C7 and skeletal isomers of C5–C7- and C8–C10 than those of the catalysts supported on NaY-zeolite, which is a desired characteristic for increasing octane value of gasoline
these days. However, deactivation with reaction time was much more pronounced on HY-zeolite-supported catalyst. When the catalyst
was prcsulfided with H,S, the stability with time on stream was enhanced and the selectivity was quite different from that
of the catalyst before presulfiding. The acidity of Y-zeolite and presulfiding of catalyst greatly influenced the activny,
selectivity and stability of Pt, Ir, Pt-Ir and Pt-Ni bimetallic catalysts supported on Y-zeolite in n-decane reforming reaction. 相似文献
169.
Yiming Zeng Zhigang Wang Lijun Wan Yanqiao Shi Guanwen Chen Chunli Bai 《应用聚合物科学杂志》2003,88(5):1328-1335
By the use of atomic force microscopy (AFM), formation mechanism of nodular structure in cellulose acetate membranes was systematically investigated. Elementary factors affecting the nodule formation were delineated on the basis of both kinetic and thermodynamic considerations. It was shown that (1) the exact nature of nodular structure is thermodynamic equilibrium glassy state; nodular structure will vanish in the rubbery state; (2) the thermodynamic factor affecting nodule formation is the membrane formation temperature; with the membrane formation temperature decreasing, more chain segments are able to form nodular structures; (3) nodule formation is dependent on the segment rearrangement; variation of the solvent environment is the major kinetic factor affecting the segment rearrangement and nodule formation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1328–1335, 2003 相似文献
170.