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21.
A so-called “three-point” (3P) method has been developed for thermal diffusivity measurements of thermal insulating materials.
One side of a cylindrical specimen, sandwiched between two thin metal plates, is subjected to intense light from an incandescent
lamp to generate a thermal perturbance. The temperature response is measured in three locations along the test specimen. Thermocouples
are located at the front and rear faces of the specimen, and the third is placed inside the specimen at a known location.
The two outside temperatures are used as boundary conditions, and the unknown thermal diffusivity is calculated from the third
temperature versus time curve. The method combines the advantages of rapid transient non-contact heating methods with the
well-defined boundary conditions of steady-state methods. The results of the 3P method are compared with those from steady-state
methods for a micro-porous insulation material and for a honeycomb structure. 相似文献
22.
Alexander Tesar Jozef Melcer 《International journal for numerical methods in engineering》2007,69(7):1446-1459
Dynamic identification and optimization of bionics shell roofs subjected to the snow skidding is dealt with in present paper. The optimization control of structural geometry in order to induce the aimed snow skidding with reduction of dead weight snow loads is aimed. Theoretical, numerical and experimental in situ assessments based on wave approaches of the problem are presented. Structural application in situ on attractive shell roof made of laminated wood with optimization control suggested is presented. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
23.
We propose a method for representing heterogeneous concept lattices as classical concept lattices. Particularly, we describe a transformation of heterogeneous formal context into a binary one, such that corresponding concept lattices will be isomorphic. We prove the correctness of this transformation by the basic theorem for heterogeneous as well as classical concept lattices. 相似文献
24.
Jozef Kula Magdalena Sikora Robert Dabrowski 《Journal of the American Oil Chemists' Society》1994,71(5):545-546
A one-step procedure is described for the synthesis of (E)-2-nonenal from commercial castor oil by ozonolysis in methanol, followed by reduction of the ozonide products with dimethyl
sulfide and exposure of the resulting intermediate product to dilute sulfuric acid. The developed process allows the production
of the aldehyde with a yield of 80% at a purity of 95%. The method has advantages over all those reported earlier, because
of inexpensive raw material and reducing agent, recycling of the solvent and its unusual simplicity. 相似文献
25.
26.
Jadwiga Sadowska Jzef Fornal Anita Ostaszyk Beata Szmatowicz 《Journal of the science of food and agriculture》1996,72(2):257-262
The possibility of using the oil-point and compression tests for evaluation of dried rapeseeds processability was examined. Seeds of initial moisture 10, 14, 18 and 22% (w/w) were dried at 60, 80, 100 and 120°C to a final moisture of 6·5% (w/w). The values of pressure ( P 0 ), work ( L 0 ) and strain (ε0) determined by the oil-point test, and pressure at strain ε=0·45 mm mm−1 ( Pε ) and degree of elasticity ( D ) determined by the compression test for bulk dried seeds differed markedly from those found for non-dried seeds. The P 0 , L 0 and Pε values were strongly correlated with the initial moisture of rapeseeds and drying temperature. All the strain values (ε0) were lower than those for non-dried seeds, and their changes depended solely on the initial moisture of seeds. Changes in the degree of elasticity were irregular and did not reach the value characteristic for overdried seeds, ie 100%. High correlation of the agglomeration test data (Δ1–3 values) with those of the P 0 , L 0 and Pε made it possible to develop appropriate equations that proved the usefulness of the variables for determining the dried rapeseed processability. 相似文献
27.
Mariana Ušáková Jozef Lukáč Rastislav Dosoudil Vladimír Jančárik Anna Grusková Elemír Ušák Jozef Sláma Jan Šubrt 《Journal of Materials Science: Materials in Electronics》2007,18(12):1183-1189
The paper is devoted to the preparation of NiZn ferrite with small substitutions of copper by means of ceramic technology.
The influence of small Cu substitution on the microstructural and magnetic properties of NiZn ferrites have been analysed
by means of various experimental methods and interpreted from the point of view of preparation technology optimisation and
possible applications of such materials. A strong correlation between the substituent content and resulting properties has
been observed, thus allowing preparation of material with the properties tailored for any particular application. 相似文献
28.
Shen Ran Jozef Vleugels Shuigen Huang Kim Vanmeensel Dave H.A. Blank Louis Winnubst 《Journal of the European Ceramic Society》2010,30(4):899-904
Nano-powder composites of 3Y-TZP doped with 8 mol% CuO were processed by spark-plasma sintering (SPS). A 96% dense composite ceramic with an average grain size of 70 nm was obtained by applying the SPS process at 1100 °C and 100 MPa for 1 min. In contrast to normal, pressureless, sintering during SPS reactions between CuO and 3Y-TZP were suppressed, the CuO phase was reduced to metallic Cu, while the 3Y-TZP phase remained almost purely tetragonal. Annealing after SPS results in grain growth and tetragonal to monoclinic zirconia phase transformation. The grain size and monoclinic zirconia phase content are strongly dependent on the annealing temperature. By combining the processing techniques studied in this work, including traditional pressureless sintering, properties of the composite ceramic can be tuned via manipulation of microstructure. Tuning the mechanical properties of dense 8 mol% CuO doped 3Y-TZP composite ceramic by utilising different processing techniques is given as an example. 相似文献
29.
Zoran Djuric Zoran Djinovic Zarko Lazic Jozef Piotrowski 《Journal of Electronic Materials》1988,17(3):223-228
A quantitative model of isothermal vapor phase epitaxy is proposed. It can be applied to both closed and open tube systems.
This model enables the prediction of compositional profiles of the layers grown by isothermal vapor phase epitaxy with dependence
on the growth parameters and thermodynamical data of the (Hg,Cd)Te system. The dependence of compositional profiles of the
ISOVPE layers on temperature and time of deposition, source to substrate spacing, mercury and inert gas pressures are discussed
for both solid and liquid sources. Modification of the compositional profiles by the postgrowth annealing has also been studied.
The proper choice of growth and annealing parameters makes the optimization of the profiles possible. The calculated profiles
are compared with the experimental data and a satisfactory quantitative fit is found in most cases. The possible reasons for
remaining discrepancies are discussed. 相似文献
30.
A range of 18 diesel fuels and 21 kerosene fuels from mainly Australian petroleum and synthetic fuel sources, including coal, shale and peat, was investigated. Compositional details were defined as the weight per cent abundances of n-alkanes, branched plus cyclic saturates, single-ring aromatics, doublering aromatics and polynuclear aromatics, using both h.p.l.c. and 13C n.m.r. techniques. Relationships between fuel composition and a range of fuel properties were sought. Simple linear relationships between property values and compositional data were used. Explicit correlative expressions were derived using multiple linear regression analysis, with the coefficient of multiple determination, R2, indicating the quality of the fit between observed and calculated property values. In most cases good correlations were achieved. For diesels the properties investigated, with R2 values in parentheses, were: inverse specific gravity (0.99); 13C n.m.r. aromaticity (0.99); 1H n.m.r. aromaticity (0.88); cetane index (0.97); aniline point (0.96); diesel index (0.98); and FIA-measured aromatics content (0.77). For kerosenes the properties, with R2 values in parentheses, were: 13C n.m.r. aromaticity (0.98); 1H n.m.r. aromaticity (0.97); smoke point (0.88); and FIA-measured aromatics content (0.94). The results are shown to be of value in assessing the potential and limitations of hydrotreating as a process for upgrading synfuels. 相似文献