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41.
Marta Gimnez-Pedrs Ali Aghmiz Carmen Claver Anna M. Masdeu-Bult Denis Sinou 《Journal of molecular catalysis. A, Chemical》2003,200(1-2):157-163
High linear alkenes (1-octene and 1-decene) have been hydroformylated using water-soluble rhodium complexes associated with sulfonated diphosphines in the presence of ionic surfactants or methanol. In all cases, the hydroformylation activities were higher than in experiments without additives. The selectivity in aldehydes was higher when we used cetyltrimethylammonium hydrogensulfate (CTAHSO4) as the surfactant or methanol as the co-solvent. 相似文献
42.
Ali. Elamin. M. Saeed 《Annals of Differential Equations》2006,22(2):127-133
The purpose of this paper is to study a general Lienard type cubic system with one antisaddle and two saddles. We give some results of the existence and uniqueness of limit cycles as well as the evolution of limit cycles around the antisaddle for system (2) in the following when parameter a1 changes. 相似文献
43.
We find the existence of a quantum thermal effect, “Hawking absorption.” near the inner horizon of the Kerr–Newman black hole. Redefining the entropy, temperature, angular velocity, and electric potential of the black hole, we give a new formulation of the Bekenstein–Smarr formula. The redefined entropy vanishes for absolute zero temperature of the black hole and hence it is interpreted as the Planck absolute entropy of the KN black hole. 相似文献
44.
In this paper we construct a positive doubly power bounded operator
with a nonpositive inverse on an AL-space. 相似文献
45.
In this paper, it is shown that some of the results of torus actions on Poincaré duality spaces, Borel’s dimension formula
and topological splitting principle to local weights, hold if ‘torus’ is replaced by ‘pro-torus’. 相似文献
46.
Koudymov A. Xuhong Hu Simin K. Simin G. Ali M. Yang J. Asif Khan M. 《Electron Device Letters, IEEE》2002,23(8):449-451
We demonstrate a novel RF switch based on a multifinger AlGaN/GaN MOSHFET. Record high saturation current and breakdown voltage, extremely low gate leakage current and low gate capacitance of the III-N MOSHFETs make them excellent active elements for RF switching. Using a single element test circuit with 1-mm wide multifinger MOSHFET we achieved 0.27 dB insertion loss and more than 40 dB isolation. These parameters can be further improved by impedance matching and by using submicron gate devices. The maximum switching power extrapolated from the results for 1A/mm 100 /spl mu/m wide device exceeds 40 W for a 1-mm wide 2-A/mm MOSHFET. 相似文献
47.
Felix Ali Mehmeti 《Mathematical Methods in the Applied Sciences》1994,17(9):697-752
Consider two copies N1, N2 of the interval [0, ∞]. Consider Klein-Gordon equations with (different) constant coefficients on ? × Nj ( = time × space). Assume the coincidence of the values of the solution at the boundary points of the Nj for all times and a transmission condition relating its first (one-sided) space derivatives at these points. Under a symmetry condition, we extend the spatial part of the equation and the transmission conditions to a self-adjoint operator (by Friedrichs extension) and reformulate our problem in terms of an abstract wave equation in a suitable Hilbert space. We derive an expansion of the solution in generalized eigenfunctions of this self-adjoint extension and show, that the L∞-norms (in space) of the solution and its first k space derivatives at the time t decay for t → ∞ at least as const. t¼, if the initial conditions satisfy a compatibility condition of order k derived in this paper. The loss of decay rate in comparison with the full line case (const. t?½, cf. [28]) is caused by the tunnel effect. Further we show that an abstract wave equation in a Hilbert space with a Friedrichs extension as spatial part can always be derived from a stationarity principle for an associated action-type functional. This yields a physical legitimation of our model by the principle of stationary action and moreover a criterion for the physical interpretability of all models created by the linear interaction concept [4, 6, 8, 10], in particular for the coupling of media of different dimension (alternative to [13, 16] for similar models). 相似文献
48.
Joel M. Kauffman Ali Khalaj Peter T. Litak John A. Novinski Gurdip S. Bajwa 《Journal of heterocyclic chemistry》1994,31(4):957-965
To improve the solubility, photostability and fluorescence quantum yield (Φ) of 2-arylbenzimidazolium ions the N-1 hydrogen was replaced by an alkyl group before N-3 was quatemized; this substitution did not reduce Φ, proving the absence of steric inhibition to attainment of coplanarity in the excited state. A related symmetrical 2,2′-arylenebis(1,3-dimethyldibenzimidazolium ion) had Φ = 0.86. The related 2,5-bis(1-methyl-2-benzimidazolyl)phenol had Φ = 0.38 at 22° as well as a very large Stokes' shift due to proton-transfer. These findings supported a new insight into the electron distribution of the first excited singlet state of oligophenylenes. The compounds are of interest as laser dyes and scintillation fluors. 相似文献
49.
50.
Compact WLAN disc antennas 总被引:1,自引:0,他引:1
McEwan N.J. Abd-Alhameed R.A. Ibrahim E.M. Excell P.S. Ali N.T. 《Antennas and Propagation, IEEE Transactions on》2002,50(12):1862-1864
A novel conical beam patch antenna design, suitable for local area network applications, uses a central cylindrical connection from the disc to ground to achieve a large reduction in resonant size. Results on efficiency, bandwidth, and pattern are reported for several prototypes. 相似文献