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991.
992.
Akbar Azam Muhammad Arshad Ismat Beg 《Rendiconti del Circolo Matematico di Palermo》2008,57(3):433-441
We prove the existence of points of coincidence and common fixed points of a pair of self-mappings satisfying a generalized
contractive condition in cone metric spaces. Our results generalize several well-known recent and classical results.
相似文献
993.
Given a star operation ∗ of finite type, we call a domain R a ∗-unique representation domain (∗-URD) if each ∗-invertible ∗-ideal of R can be uniquely expressed as a ∗-product of pairwise ∗-comaximal ideals with prime radical. When ∗ is the t-operation we call the ∗-URD simply a URD. Any unique factorization domain is a URD. Generalizing and unifying results due to Zafrullah [M. Zafrullah, On unique representation domains, J. Nat. Sci. Math. 18 (1978) 19-29] and Brewer-Heinzer [J.W. Brewer, W.J. Heinzer, On decomposing ideals into products of comaximal ideals, Comm. Algebra 30 (2002) 5999-6010], we give conditions for a ∗-ideal to be a unique ∗-product of pairwise ∗-comaximal ideals with prime radical and characterize ∗-URD’s. We show that the class of URD’s includes rings of Krull type, the generalized Krull domains introduced by El Baghdadi and weakly Matlis domains whose t-spectrum is treed. We also study when the property of being a URD extends to some classes of overrings, such as polynomial extensions, rings of fractions and rings obtained by the D+XDS[X] construction. 相似文献
994.
N. Muhammad S. Ali S. Shahzadi A. N. Khan 《Russian Journal of Coordination Chemistry》2008,34(6):448-453
Oxovanadium(IV) complexes with four different non-steroidal anti-inflammatory drugs have been synthesized. These complexes
were characterized by different analytical techniques such as CHN, IR, UV-Vis spectroscopy, and mass spectrometry. The IR
data show the bidentate nature of the ligands and reveal hexacoordinate geometry in the solid state. The complexes were tested
for their biological activity against six different bacterial strains and plant pathogens, and all complexes showed good biological
activity with few exceptions
The text was submitted by the authors in English. 相似文献
995.
996.
Masoud Alimardani Ehsan Toyserkani Jan P. Huissoon Christ P. Paul 《Optics and Lasers in Engineering》2009,47(11):1160-1168
Parts fabricated using laser solid freeform fabrication (LSFF) are subject to thermal stresses due to the layer-by-layer material deposition and the temperature distribution characteristic throughout the process domain. The thermal stress patterns and intensity contribute significantly to potential delamination and crack formation. In this paper, the temperature distribution and stress field induced during the multilayer LSFF process, and their correlation with delamination and crack formation are studied. This is performed by a numerical and experimental investigation in the fabrication of a thin wall of 304L stainless steel. For time-dependent predictions on the locations of maximum temperatures and thermal stresses and their patterns, a three-dimensional (3D) transient finite element model is employed to simulate the process, including the geometry of the deposited materials as well as coupled temperature and stress distributions across the process domain. The experimental results are used to verify the numerical results as well as to investigate the correlation between the numerical results and micro-crack formations across the fabricated parts. The experiments are conducted with the same process parameters used in the numerical analyses using a 1 kW Nd:YAG pulsed laser. The trend of numerical and experimental results reveals that by preheating the substrate prior to the fabrication process, it is possible to substantially reduce the micro-cracks formed across the part. To demonstrate the feasibility of preheating on the reduction of micro-cracks, several simulations and experiments are performed in which a crack-free result is obtained when the substrate is preheated to 800 K. For this case, 22% reduction in thermal stresses is obtained throughout the process domain. 相似文献
997.
Muhammad A. Rashid Bettina Appel Vahuni Karapetyan Helmut Reinke Peter Langer 《Tetrahedron》2008,64(22):5416-5425
Functionalized 1-azaxanthones (5-oxo-5H-[1]-benzopyrano[2,3-b]pyridines) were prepared by TMSOTf-mediated condensation of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with 3-cyanochromones and subsequent base-mediated domino ‘retro-Michael/nitrile-addition/heterocyclization’ reaction. 相似文献
998.
999.
Muhammad Taher Abuelmaatti 《International Journal of Infrared and Millimeter Waves》2007,28(10):849-858
A mathematical model for the relationship between the output voltage and incident radiation of the infrared semiconductor
mercury-cadmium-telluride (MCT) detector is presented. The model, basically a sine-series function, can easily yield closed-form
expressions for the harmonic and intermodulation performance of the MCT detector with large-amplitude multisinusoidal incident
radiation. The special case of two-tone equal-amplitude incident radiation is considered in detail. The results show that
the second-order harmonic and intermodulation products are always higher than the third-order components. Moreover, the results
show that the second-order intermodulation is always dominant. 相似文献
1000.
Muhammad Taher Abuelmaatti 《International Journal of Infrared and Millimeter Waves》2007,28(9):741-749
A mathematical model for the temperature dependence of the bolometer semiconductor resistance is presented. The model, basically
a sine-series function, can easily yield closed-form expressions for the harmonic and intermodulation performance of the acquired
interferogram voltage with large-amplitude multisinusoidal variations in the incident radiation. The special case of two-tone
equal-amplitude incident radiation is considered in detail. The results show that the intermodulation components are always
higher than the harmonic components of the same order. The results also show that the second-order intermodulation is always
dominant and is higher than the second-harmonic component by about 6 dB. Moreover, the results show that for relatively small
incident amplitudes of the incident radiation the ratio between the second- and third-harmonic components is almost equal
to the ratio between the second-harmonic component and the fundamental. The results also show that the ratio between the amplitudes
of the second- and third-order intermodulation components is almost equal to the ratio between the amplitudes of the second-order
intermodulation component and the fundamental. 相似文献