The determination of the solidification characteristics of alloys using differential scanning calorimetry (DSC) is difficult because of the unknowns associated with the kinetic of phase transformations and the thermal resistance between the sample and the temperature measuring device. This paper shows how appropriate assumptions coupled with a thermodynamic software package and an accurate mathematical analysis of a power-compensated DSC, can enable a direct comparison between the experimental and the theoretical heat evolutions obtained during the solidification of a multiphase alloy. This comparison is helpful in order to assess the thermodynamic database and to validate the different assumptions made in the solidification model.
Studying the dynamics of solitons in nonlinear time-fractional partial differential equations has received substantial attention, in the last decades. The main aim of the current investigation is to consider the time-fractional Sharma–Tasso–Olver–Burgers (STOB) equation in the Caputo–Fabrizio (CF) context and obtain its valid approximations through adopting a mixed approach composed of the homotopy analysis method (HAM) and the Laplace transform. The existence and uniqueness of the solution of the time-fractional STOB equation in the CF context are investigated by demonstrating the Lipschitz condition for $\varphi \left(x,t;u\right)$ as the kernel and giving some theorems. To illustrate the CF operator effect on the dynamics of the obtained solitons, several two- and three-dimensional plots are formally considered. It is shown that the mixed approach is capable of producing valid approximations to the time-fractional STOB equation in the CF context. 相似文献
Yttrium reacts with 5-(4'-chlorophenylazo)-6-hydroxypyrimidine-2,4-dione (I), 5-(2'-bromophenylazo)-6-hydroxypyrimidine-2,4-dione (II), 5-(2',4'-dimethylphenylazo)-6-hydroxypyrimidine-2,4-dione (III), 5-(4'-nitro-2',6'-dichlorophenylazo)-6-hydroxypyrimidine-2,4-dione (IV), 5-(2'-methyl-4'-hydroxyphenylazo)-6-hydroxypyrimidine-2,4-dione (V) to form a dark pink complexes, having an absorption maximum at 610, 577, 596, 567 and 585 nm, respectively. The complex formation was completed spontaneously in theil buffer solution and the resulting complex was stable for at least 3 h after dilution. Under the optimum conditions employed, the molar absorptivities were found to be 1.60 x 10(4), 1.29 x 10(4), 1.96 x 10(4), 1.45 x 10(4) and 1.21 x 10(4) l mol(-1) cm(-1) and the molar ratios were (1:1) and (1:2) (M:L). The linear ranges were found within 95 microg of yttrium in 25 ml solution. One of the characteristics of the complex was its high tolerance for calcium and hence a method of separation and enrichment of microamounts of yttrium by using calcium oxalate precipitate was developed and applied to measure yttrium in nickel-base alloys. Interfering species and their elimination have been studied. The precision and recovery are both satisfactory. 相似文献
Delayed self-organized criticality is defined. It is shown to preserve the power-law behavior of self-organized criticality
with a significant change in the exponents. A delayed version of the Ito—Matsuzaki model for earthquakes is constructed and
studied. This model explains some fractal features of earthquakes as well as the Gutenberg-Richter and Omori laws. Furthermore
theb value obtained from the delayed model is closer to observations than theb value of the undelayed model. 相似文献
A new diimide-diacid, (4-(4-(2,6-diphenylpyridin-4yl)phenoxy)phenyl)-1,3-bis(trimellitimidobenzene) (PPMIB), was synthesized from the condensation reaction of a new diamine, (4-(4-(2,6-diphenylpyridin-4yl)phenoxy)phenyl)-3,5-diaminobezamide (PPDA), and trimellitic anhydride carboxylic acid (TMAA) in glacial acetic acid. The diimide-diacid (PPMIB) was characterized by FT-IR, 1H-NMR and elemental analysis. A series of novel aromatic poly(amide-imide)s (PAIs) was synthesized by using direct polycondensation of PPMIB with various diamines in NMP in the presence of triphenylposphite and pyridine as condensing agents. The resulting PAIs were amorphous, readily soluble in many polar aprotic solvents and showed inherent viscosities of 0.35–0.50 dL/g. According to thermal analysis, these polymers exhibited glass transition temperatures (Tgs) in the range of 202–280°C and temperature of 10% weight loss (T10) varied from 400 to 545°C in N2. These polymers in NMP solution exhibited strong UV-Vis absorption maxima at 320°C nm and their fluorescence emission peaks appeared around 410–565 nm. 相似文献
Lignocelluloses industrial waste flour of olive husk powder (LCF) was utilized as reinforcement in carboxylated nitrile butadiene rubber (XNBR)/Polyamide-12 (PA-12) thermoplastic elastomer composites. To improve the bonding quality between the LCF and the blend, the powder was chemically treated by two means, the former is the treatment with toulene-2–4-diisocyanate (TDIC), and the latter is mercerization with sodium hydroxide followed by neutralization with acetic acid. The untreated and chemically treated powders were analyzed with attenuated total reflectance infrared spectroscopy (ATR-IR). The morphology of the powders before and after treatment was studied with scanning electron microscopy (SEM). The LCF reinforced composites were prepared using computerized Haake internal mixer coupled with rheometer. The processing conditions were 178°C and rotor speed of 80- round per minute for 7 min. The melt mixing process was monitored by the torque-time plastograms of the Haake internal mixer. The development of the stock temperature during the mixing process was monitored using the rheometer of Hakke internal mixer. The structural changes of the XNBR/PA-12 composites were inspected by SEM and attenuated ATR-IR spectroscopy. The influence of the modified filler on the toughness and hardness of the prepared samples are reported. The resistance of the prepared composites to water and toluene swelling are evaluated as well. 相似文献
Structural Chemistry - In the present work, a molecular electron density theory (MEDT) study is carried out to shed light on the regio- and stereochemistry in two Diels–Alder (DA) reactions... 相似文献
A ferrocenyl ligand 1 was prepared from condensation of 5-methyl-2-furaldehyde with l,l′-diacetylferrocene dihydrazone. This ligand forms 1:1 complexes with cobalt(II), nickel(II), copper(II) and zinc(II) 2–5 in good yield. Characterization of the ligand and complexes was carried out using infrared, nuclear magnetic resonance, mass spectra, electronic absorption, magnetic susceptibility, molar conductivity, and elemental analysis. Cytotoxic activity of the prepared ligand and its complexes were tested against different human cancer cell lines. The results suggested that the synthesized compounds were more potent than the comparative standards drugs used in most cases, whereas they had less activity in the others. 相似文献