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31.
Over the past few years, the field of architecture has witnessed revolutionary changes in design. The recent completions of Frank O. Gehry’s projects brought unprecedented attention to complex-shaped, nonconventional design. In following these latest trends, the author has been drawn to the issue concerning the structural systems currently being adopted in realizing these complicated designs. It is perhaps inevitable that the traditional structural systems, comprised of structural elements suitable for use in conventional linear shapes, face tremendous challenges and limitations in building such complicated designs. In this context, this research consists of proposing a new alternative by employing “boundary structures with continuously changing curvature,” which follow the complex-curved envelope surface, as well as fabricating an experimental model made of polymer composite materials with computer-aided design/computer-aided engineering/computer-aided manufacturing technologies. Consequently, the study aims at offering architects unprecedented freedom in design and a new paradigm for realizing their creative ideas. 相似文献
32.
Erian A. Armanios 《Canadian Metallurgical Quarterly》1991,4(2):216-235
A validation of the delamination analysis models developed in a companion paper is provided through comparisons of predictions with finite‐element and elasticity solutions. The models are applied to the analysis of composite compression specimens reinforced with end tabs. An elasticity solution for the gage section of the specimens is developed. A comparison of the characteristic roots shows that the predictions of the models include the material and geometric parameters that control the behavior, and the roots corresponding to the basic stretching and bending modes are accurately predicted. The stress distribution at the interface between tabs and specimen is in good agreement with a finite‐element simulation. The interlaminar shear and peel stresses show an exponential increase with a maximum intensity at the free edges of the tabs. The behavior of previously tested specimens is explained; and practical guidelines for specimen design are provided to avoid unwanted extraneous modes of failure. The influence of the deformation modes associated with each model is investigated. An assessment of the accuracy and level of complexity is presented. 相似文献
33.
En-Hai Sun Yong-Ho Choa Tohru Sekino Tomohiko Adachi Koichi Niihara 《Materials Research Innovations》2002,6(3):105-111
Cordierite/ZrO2 composites with 5 to 25 wt% ZrO2 were fabricated by conventional powder mixing and pressureless sintering method. Their densification behavior, microstructure,
mechanical and thermal properties were studied. By dispersing 25 wt% (9.57 vol%) ZrO2, densified cordierite/ZrO2 composite with a relative density of 98.5% was obtained at an optimum sintering condition of 1440 °C and 2 h. ZrO2 particles were homogenously dispersed within matrix grains and at the grain boundaries. The intragranular particles were
finer than 100 nm and the intergranular particles were coarser. Both fracture strength and toughness could be enhanced more
than two times higher, compare to those of monolithic cordierite, by dispersing 25 wt% ZrO2 into the cordierite matrix. The toughening mechanism in the present composites was mainly attributed to martensitic transformation
due to ZrO2 dispersion.
Electronic Publication 相似文献
34.
The magnetic properties of polyethersulfone-matrix composites with 3-19 vol.% polycrystalline nickel filaments (0.4 (im diam)
were investigated. These filaments were found to exhibit hysteresis energy loss 10800 J/m3 of nickel and coercive force 16.9 kA/m, compared to corresponding values of 4930 J/m3 and 4.7 kA/m for 2 μ.m diam polycrystalline nickel fibers, 1020 J/m3 and 0.5 kA/m for 20 μm diam polycrystalline nickel fibers, and 1280 J/m3 and 2.3 kA/m for solid polycrystalline nickel. 相似文献
35.
P. T. Tsilingiris 《国际能源研究杂志》1991,15(9):723-730
The paper describes the calculation of the beam solar radiation transmission across the uniform salinity upper convecting zone (UCZ) and the salinity stratified gradient zone (GZ), when the extinction coefficient is not only wavelength but also salinity-concentration dependent, assuming that the effect of scattering to be negligible. The results are useful in determining the effects of dissolved salt ions on pure water transmission, at least according to the existing measured data in the literature. 相似文献
36.
丁腈橡胶/导电粒子复合材料的正温度系数(PTC)特性 总被引:7,自引:0,他引:7
将导电粒子碳黑和铜粉分别与丁腈橡胶混合制备导电聚合物复合材料,其中碳黑(N550)/丁腈橡胶复合材料的电阻率随温度的变化呈现较强的正温度系数(PTC)效应。讨论了掺入导电粒子浓度、结构和表面性质以及混炼硫化工艺等对该类材料的室温电阻率及PTC效应的影响。 相似文献
37.
Te-Yu Wei Shih-Yuan Lu Yu-Cheng Chang 《Journal of the Chinese Institute of Chemical Engineers》2007,38(5-6):477-481
Tin oxide–silica composite aerogels were successfully prepared with a co-fed precursor sol–gel process. The crystallinity of the tin oxide nanoparticles, embedded in the mesoporous SiO2 network, was improved with increasing the post-reaction thermal treatment temperature. The composite aerogels exhibited a rich photoluminescence (PL) emission contributed by both SnO2 and SiO2. The PL peak of 346 nm was from the near band edge emission of the tin oxide nanoparticles, and the ones located at 310 and 476 nm were attributable to the oxygen deficiencies of the silica network. Three more emission peaks, 387, 432, and 522 nm, were observed, with the 387 nm peak contributed by the oxygen vacancies VO++, the 432 nm peak by the Sn interstitials, and the 522 nm peak by the oxygen vacancies VO+, respectively, of the tin oxide nanoparticles. The intensities of these three defect level emissions were found decreased, as compared to that of the near band edge emission, with increasing the post-reaction thermal treatment temperature as the tin oxide crystallinity improved. 相似文献
38.
In this paper a micromechanics model using the concentric cylinder assemblage model and the Mori-Tanaka average stress scheme is used to predict the static strength of unidirectional angle ply laminates. The predicted strengths agree with experimental results for Glass/Epoxy and Graphite/Epoxy systems. 相似文献
39.
This study describes the development of multilayer metal-dielectric graded index solar selective coatings in which the metallic volume fraction increases with depth, from top (air–film interface) to bottom (film–substrate interface). The work is based on computer simulation followed by validation through fabrication of the coatings and optical measurements. The influence of the choice of the number of layers present in a graded index composite selective absorber and results obtained for a new destructive interference bilayer (four-layer system) coating, designed using the computer model, were studied. The design and optimization of the composite coating was undertaken using a computer tool developed within this program of research employing Bruggeman and Maxwell–Garnett effective medium formalisms. The design tool enabled all key design parameters, with the exception of particle size and orientation, to be varied systematically to permit the sensitivity of the optical properties of the selective absorber coating to be studied.The model was validated with a supporting program of experimental research in which many different selective absorbers were prepared by co-sputtering of metal and dielectric materials.Although the best compositional gradation can be achieved by increasing the number of layers, the variation in optical performance beyond a certain number of layers is minimal. The destructive interference produced between adjacent layers contributes to the absorptance. The effect of the number of layers (single, four and 10) has been calculated for various materials such as nickel, vanadium, tungsten, cobalt and chromium based coatings. Solar absorptance of 0.98 and 0.96 was achieved by simulation and experimental findings with less than 0.07 thermal emittance at 300 K for 200 nm thick, 4-PGSAC (four-layer system) of V : Al2O3 composites. Other designs showed lower optical performance for all the material combinations regardless of their individual optical properties. Use of such thin film coating on the absorbers of solar thermal appliances can reduce thermal losses significantly, which could be of importance to the relevant industry. 相似文献
40.