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51.
O. Acselrad I. S. Kalashnikov E. M. Silva M. S. Khadyev R. A. Simao 《Metal Science and Heat Treatment》2006,48(11-12):543-553
The phase composition and the morphology of structures formed as a result of isothermal holds in the range of aging temperatures of hardened alloy Fe-28% Mn, 8.5% Al-1% C-1.25% S are studied. A diagram of the decomposition of initial austenite is plotted starting with the early stages and ending with the moment when the system attains the equilibrium state. 相似文献
52.
J. J. Rêgo Silva L. C. Wrobel J. C. F. Telles 《International journal for numerical methods in engineering》1993,36(10):1661-1679
This paper presents a new family of continuous/discontinuous three-dimensional boundary elements which has been implemented in a computer system for acoustic wave propagation in the frequency domain. The system includes elements of different geometrical shapes, 'order of interpolation and degree of continuity. Results of several tests are included to show the efficiency of the family of elements. 相似文献
53.
M. A. R. Buzalaf B. S. de Almeida V. E. da Silva Cardoso K. P. K. Olympio T. de Almeida Furlani 《Food Additives & Contaminants》2004,21(3):210-215
Total fluoride (TF) and HCl 0.01 M ('gastric juice')-soluble fluoride (SF) were analysed in infant foods, beverages and calcium-rich biscuits. Samples were divided into seven categories: children cereals (A), chocolate-flavoured milk (B), soy beverages (C), filled biscuits (D), non-filled biscuits (E), wafer biscuits (F) and corn starch biscuits (G). Mean TF concentrations ± SD (amplitude, unit µg F ml-1 or µg F g-1) were: (A) 4.25 ± 3.04 (0.20 - 7.84, n = 6); (B) 0.34 ± 0.47 (0.05-1.27, n = 6); (C) 0.15 ± 0.07 (0.09-0.29, n = 8); (D) 8.44 ± 1.76 (7.65-10.47, n = 4); (E) 12.41 ± 1.15 (10.69-13.68, n = 4); (F) 0.35 ± 0 (0.34-0.36, n = 4) and (G) 7.77 ± 1.12 (6.86-8.68, n = 2). Five samples of cereals, one sample of chocolate-flavoured milk and 10 samples of biscuits were analysed for SF. In cereals analysed for SF, all fluoride was soluble, while for the chocolate-flavoured milk, approximately 50% of TF was soluble. Regarding the biscuits analysed for SF approximately 20% of TF was soluble. It was observed that some of the cereals and beverages, and most of the biscuits analysed, might be important contributors to total daily fluoride intake. When consumed just once per day, cereals and beverages might supply up to 25% of the maximum recommended daily fluoride intake (0.07 mg F kg-1 body weight) for a 2-year-old child (12 kg). For the filled, non-filled and corn starch biscuits, when 3, 32 or 20 units of them, respectively, are consumed just once per day, they may supply up to 16% of the maximum recommended daily fluoride intake. However, only approximately 25% of fluoride absorption occurs from the stomach and 75% from the small intestine. Therefore, a higher fluoride bioavailability is possible. 相似文献
54.
Renato Cataluña Rosângela da Silva Eliana Weber de Menezes Ricardo Boeira Ivanov 《Fuel》2008,87(15-16):3362-3368
Oxygenated fuels increase fuel consumption due to their low enthalpy of combustion; however, their high antiknock index renders them suitable for use in engines with a high compression rate, increasing their thermal yield. This study evaluated the performance of biorenewable oxygenated fuels (ethanol and isoamyl alcohol) and partially renewable fuels (ETBE: ethyl tert-butyl ether, TAEE: tert-amyl ethyl ether and di-TAE: di-tert-amyl ether) with high degree of purity and in mixtures with automotive gasoline, based on tests with Otto cycle engines. Among the oxygenated fuels evaluated here, di-TAE was found to present the best characteristics of performance, both individually and in mixtures with gasoline. 相似文献
55.
Increase in the ion concentration in the medium was found to increase conductivity and potassium hydroxide number (KOH No) in natural rubber latex (NRL). Addition of long chain fatty acids can increase the ion concentration in the medium and stability of NRL. A series of concentrated natural rubber latex samples from three different areas with different soils and climatic conditions were tested for the parameters such as KOH No and conductivity. They have been measured over a period of 62 days, upon addition of soap to natural rubber latex concentrate. The result showed that there was a strong positive linear correlation between conductivity and KOH No. The regression equation to express the relationship between the variables has also been found. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 相似文献
56.
Steady-State Control Reference and Token Conservation Laws in Continuous Petri Net Systems 总被引:1,自引:0,他引:1
Mahulea C. Ramirez-Trevino A. Recalde L. Silva M. 《Automation Science and Engineering, IEEE Transactions on》2008,5(2):307-320
This paper addresses several questions related to the control of timed continuous Petri nets under infinite server semantics. First, some results regarding equilibrium states and control actions are given. In particular, it is shown that the considered systems are piecewise linear, and for every linear subsystem the possible steady states are characterized. Second, optimal steady-state control is studied, a problem that surprisingly can be computed in polynomial time, when all transitions are controllable and the objective function is linear. Third, an interpretation of some controllability aspects in the framework of linear dynamic systems is presented. An interesting finding is that noncontrollable poles are zero valued. 相似文献
57.
Herman Keith C.; Ostrander Rick; Walkup John T.; Silva Susan G.; March John S. 《Canadian Metallurgical Quarterly》2007,75(5):716
A latent profile analysis was conducted on the co-occurring symptoms of 423 adolescents diagnosed with major depressive disorder as part of the Treatment for Adolescents with Depression Study (TADS), a multisite, randomized treatment trial. The participants had a mean (SD) age of 14.6 (1.5) years; of the sample, 45.6% was male and 73.8% was white. Scores on the primary subscales of Conners' Parent Rating Scale-Revised were used as indicators in the analysis. Five classes of symptoms best described the clinical presentation of adolescents enrolled in the TADS. Of the adolescents in the sample, 80% were assigned to classes with clinically significant elevations on 1 or more subscales of the Children's Depression Rating Scale-Revised. The 5 classes met empirical criteria for distinctiveness and were validated against clinical diagnoses, child-rated symptoms, and clinician-rated functional impairment. The findings are consistent with prior studies that showed a high rate of co-occurring symptoms among depressed adolescents. The discussion focuses on understanding subtypes and comorbidity in adolescent depression as well as the implications for treatment and for prevention. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
58.
We describe the design and operation of a new high-pressure metal ebulliometer which can operate at pressures to at least 3 MPa in the range 220–400 K. Infinite-dilution activity coefficients are presented for the system CHF2Cl + CF3-CH, at 275 K and for the system CF3-CH2F + CH2F2, at 260, 230, and 300 K. The Wilson activity coellicient model and a virial coefficient model are applied to these systems, and the phase equilibrium conditions are calculated. The results are shown to agree well with predicted and with published measured values. The excess enthalpy is calculated and compared with results from a Peng Robinson equation of state. Vapor densities on the dew curves are given. 相似文献
59.
J. D. Carey R. C. Smith S. R. P. Silva 《Journal of Materials Science: Materials in Electronics》2006,17(6):405-412
The influence of the different types of bonding present in a range of carbon based materials is discussed as a precursor to
describing the field emission characteristics of carbon cold cathode materials. Some of the controlling factors which govern
electron emission from carbon based cathodes are discussed. It is shown that from disordered carbon films the interplay between
the clustered sp2 phase and the insulating sp3 matrix is important. The transition from a ‘back contact’ to ‘front surface’ controlled emission mechanism is described in
terms of the sp2 content and field penetration. A possible reason for high field enhancement factors found in disordered films also is provided.
It is further shown that changes to the sp2 phase by current stressing can improve the field emission characteristics. Emission from carbon nanotubes is also discussed
and the prospects for new types of nanotube – polymer composite based cathodes are also considered. 相似文献
60.
Suely P. Freitas Fernando C. Da Silva Regina C. A. Lago & Raad Y. Qassim 《International Journal of Food Science & Technology》1996,31(4):319-325
Shear rate vs. shear stress data were obtained on avocado pulp in water emulsions using a concentric cylinder rheometer and fitted to a power law model. Dilution, as volume fraction of water, had a pronounced effect on the apparent viscosity of the pulp emulsions and the Richardson equation, (ηR = exp.( a φ) for the emulsion viscosity fitted the data well. A mean slope coefficient, a , of 4.57 can be used as a first approximation. Enzymatic treatment (40°C, 1 h), is slightly more effective than thermal treatment (65°C, 1 h), in reducing the initial apparent viscosity of the pulp-water emulsions 相似文献