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71.
<正>A series of novel unsymmetrical N-(4-oxo-2-phenyl-3(4H)-quinazolinoyl)-N-(aryl) acetamidines was synthesized by reacting ethyl(1H)-N-(4-oxo-2-phenylquinazolin-3(4H)-y1)ethanimidoate(2) and suitable reactive aromatic amines.Structures' determination of the synthesized compounds was carried out using spectroscopic techniques including IR,~1H NMR,and mass spectrometry. Structural effects on reactivity were also studied. 相似文献
72.
Ahmad VU Zubair M Abbasi MA Kousar F Rashid MA Rasool N Tareen RB 《Natural product research》2006,20(1):69-74
Phytochemical investigation of Platytaenia multicaule resulted in the isolation of two new ceramides, N-triacontylpentadecanamide and 1,3,4-trihydroxy-2,dodecanoylamino-(24E)-unacotenene, along with two known compounds, beta-sitosterol and beta-sitosterol glycoside. The structure elucidation of the isolated compounds was based primarily on 1D and 2D NMR analyses, including COSY, NOESY, HMQC, and HMBC correlations. 相似文献
73.
Farooq Umar Hossein Raza Hamdani Anwar‐ul‐Haque Sajid Raza Chaudhry Khalid Parvez 《国际流体数值方法杂志》2009,59(2):173-194
The effect of various reduced frequencies has been examined for an oscillating aspect ratio 10 NACA 0015 wing. An unsteady, compressible three‐dimensional (3D) Navier–Stokes code based on Beam and Warming algorithm with the Baldwin–Lomax turbulence model has been used. The code is validated for the study against published experimental data. The 3D unsteady flow field is simulated for reduced frequency values of 0.1, 0.2 and 0.3 for a fixed mean angle of attack position and fixed amplitude. The type of motion is sinusoidal harmonic. The force coefficients, pressure distributions and flow visualization show that at the given conditions the flow remains attached to the wing surface even at high angles of attack with no clear separation or typical light‐to‐deep category of dynamic stall. Increased magnitude of hysteresis and higher gradients are seen at higher reduced frequencies. The 3D effects are even found at midspan locations. In addition, the rate of decrease in lift near the wing tips compared with the wing root is not much like in the static cases. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
74.
75.
Bottoli CB Chaudhry ZF Fonseca DA Collins KE Collins CH 《Journal of chromatography. A》2002,956(1-2):121-128
Modifications have been made to the method of ion-exclusion pre-separation followed by ion exchange with conductivity detection for the determination of trace levels of chloride, sulfate and nitrate in concentrated phosphoric acid. Ion-exclusion separation and pre-concentration of impurity anions is performed using Dionex AS6-ICE and AS11-HC (4 mm) columns, respectively, with water eluent. Final separation is performed using Dionex AG11-HC and AS11-HC (2 mm) columns, KOH gradient elution, and suppressed conductivity detection. Improvements to the method include addition of an autosampler and eluent generator, and use of external standard calibration. These instrumental and procedural changes significantly improve the method's throughput, while the method's capability relative to phosphoric acid specifications is maintained, as verified through statistical evaluation of control sample analyses. Detection limits of 60, 680, and 4,0 ppb (w/w) are obtained vs. semiconductor-grade phosphoric acid specifications of 1000, 12,000, and 5000 ppb for chloride, sulfate, and nitrate, respectively. 相似文献
76.
77.
Musarat Jan Aijaz Ahmad Dar Adil Amin Nuzhat Rehman Ghulam Mohammad Rather 《Colloid and polymer science》2007,285(6):631-640
The study is focused on evaluation of clouding phenomena of the aqueous single nonionic surfactant system Triton X-100 (TX-100)
and its mixed systems with anionic aerosol-OT (AOT) and cationic dodecylpyridinium chloride (DPC) in presence of hydrophobic
ions furnished by sodium salts of carboxylic acids, viz., sodium ethanoate, sodium propanoate, sodium butanoate, and sodium
hexanoate and the respective carboxylic acids [ethanoic acid, propanoic acid, butanoic acid, and hexanoic acid]. The influence
of salts on the cloud point (CP) has been explained on the basis of salt effect as well as the solubilization of higher alkyl
chain hydrophobic ions furnished by these salts. Moreover, the co- and counterion effect has been taken into account to explain
the variation of the CP in the mixed systems. However, the effect of acids on CP has been explained in the light of their
aqueous solubility and their partitioning ability between octanol and water as reflected by their K
OW values. 相似文献
78.
Kim James J. Down Douglas G. Chaudhry Mohan Banik Abhijit Datta 《Methodology and Computing in Applied Probability》2022,24(3):1297-1321
Methodology and Computing in Applied Probability - We consider an extended form of the MX/M/c queue with two types of server groups: Static as well as dynamic (which turn on/off in a... 相似文献
79.
A complete distribution for the system content of a discrete-time multi-server queue with an infinite buffer is presented, where each customer arriving in a group requires a deterministic service time that could be greater than one slot. In addition, when the service time equals one slot, a complete distribution for the delay is also presented. 相似文献
80.
A closed-form model for the computation of temperature and heat flux distribution in a semi-infinite solid when subjected to spatially decaying, instantaneous laser source is investigated. The appropriate dimensionless parameters are identified and the reduced temperature and heat flux as a function of these parameters are presented in the graphic form. Some special cases of practical interest are also discussed. It is demonstrated that the present analysis covers the classical case of no heat generation in the solid as well as some new solutions.
Wärmeleitung in einem halbunendlichen Körper, der plötzlich durch eine mit zunehmender Eindringtiefe abklingende Laser-Wärmequelle beaufschlagt wird
Zusammenfassung Es wird ein geschlossenes Rechenmodell zur Ermittlung der Temperatur- und Wärmeflußverteilung in einem halbunendlichen Körper untersucht, der plötzlich durch eine mit der Eindringtiefe abklingende Laserquelle beaufschlagt wird. Die normierten Temperaturen und Wärmeflüsse sind als Funktionen relevanter Kenngrößen graphisch dargestellt. Spezialfälle von praktischem Interesse werden diskutiert. Die vorliegende Untersuchung liefert neben einigen neuen Lösungen auch das Ergebnis für den klassischen Fall, daß keine Wärmequellen wirksam sind.相似文献