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排序方式: 共有271条查询结果,搜索用时 328 毫秒
31.
32.
An analytical forward model and numerical algorithm for retrieving the parameters of water cloud of earth atmosphere from optical measurements carried out by satellite-based lidars is presented. The forward model, based on the analytical solution of the radiative transfer equation, is used to fit the temporal profile of the laser light pulses backscattered from the cloud layers. The cloud parameters extracted from the analysis at each position on earth include the transport mean free path, the average radius of water drops, the density of drops, the scattering length, the scattering cross section, the anisotropy factor, and the altitude of top level of major clouds. Also estimated is the possible thickness of cloud layers. The efficacy of the approach is demonstrated by generating parameters of water cloud using the data collected by NASA's cloud-aerosol lidar and infrared pathfinder satellite observations (CALIPSO) satellite when it passed through North America on August 7, 2007. 相似文献
33.
We derive trace formulas for a pair of self-adjoint operators and H under the assumption that is in a Schatten class. This extends the trace formulas of [8], where V alone is assumed to be in a Schatten class. Our trace formulas apply, in particular, in the setting of differential operators and are based on Taylor-like approximations of operator functions. This significantly improves non-Taylor based trace formulas of [10]. 相似文献
34.
The velocity potentials due to the presence of a horizontal circular ring of wave sources of timedependent strength in water of finite constant depth with a floating elastic plate or a floating membrane are determined. The uniform bottom is composed of non-dissipative porous medium. The problems are formulated as the initial value problems and the Laplace transform method is used to solve these. For time-harmonic source strength, the steady-state analysis of the potentials reveals the existence of outgoing progressive waves. Graphs for the surface profiles are presented for different values of the tension parameter for the membrane, flexural rigidity of ice and the porous-effect parameter. 相似文献
35.
Baidya T Gayen A Hegde MS Ravishankar N Dupont L 《The journal of physical chemistry. B》2006,110(11):5262-5272
Nanocrystalline Ce(1)(-)(x)Ti(x)O(2) (0 < or = x < or = 0.4) and Ce(1-)(x)(-)(y)Ti(x)Pt(y)O(2)(-)(delta) (x = 0.15, y = 0.01, 0.02) solid solutions crystallizing in fluorite structure have been prepared by a single step solution combustion method. Temperature programmed reduction and XPS study of Ce(1)(-)(x)Ti(x)O(2) (x = 0.0-04) show complete reduction of Ti(4+) to Ti(3+) and reduction of approximately 20% Ce(4+) to Ce(3+) state compared to 8% Ce(4+) to Ce(3+) in the case of pure CeO(2) below 675 degrees C. The substitution of Ti ions in CeO(2) enhances the reducibility of CeO(2). Ce(0.84)Ti(0.15)Pt(0.01)O(2)(-)(delta) crystallizes in fluorite structure and Pt is ionically substituted with 2+ and 4+ oxidation states. The H/Pt atomic ratio at 30 degrees C over Ce(0.84)Ti(0.15)Pt(0.01)O(2)(-)(delta) is 5 and that over Ce(0.99)Pt(0.01)O(2)(-)(delta) is 4 against just 0.078 for 8 nm Pt metal particles. Carbon monoxide and hydrocarbon oxidation activity are much higher over Ce(1-)(x)(-)(y)Ti(x)Pt(y)O(2) (x = 0.15, y = 0.01, 0.02) compared to Ce(1)(-)(x)Pt(x)O(2) (x = 0.01, 0.02). Synergistic involvement of Pt(2+)/Pt degrees and Ti(4+)/Ti(3+) redox couples in addition to Ce(4+)/Ce(3+) due to the overlap of Pt(5d), Ti(3d), and Ce(4f) bands near E(F) is shown to be responsible for improved redox property and higher catalytic activity. 相似文献
36.
The goal of this article is to extend some results of Popescu (Probab. Theory Relat. Fields 144:179, 2009) in several directions. We establish the limiting spectral distribution (LSD) for r-diagonal matrices under reduced moment conditions compared to those required by Popescu. We also deal with the joint convergence of several sequences of such matrices. In particular, we show that there is a large class of such matrices where the joint limit is not free while the marginals are semicircular. We also consider matrices of the form $X_{n}X_{n}^{T}$ where X n is a sequence of nonsymmetric r-diagonal random matrices and establish their limiting spectral distribution. 相似文献
37.
Ridaphun Nongrum George Kupar Kharmawlong Jims World Star Rani Noimur Rahman Arup Dutta Rishanlang Nongkhlaw 《Journal of heterocyclic chemistry》2019,56(10):2873.-2883
The development of a metal‐free protocol for transformations in organic synthesis offers a significant potential environmental benefit. This article reports the exploration of meglumine, a nontoxic and biodegradable amino sugar, as an organocatalyst for the synthesis of biologically active 1H‐dibenzo[b,e][1,4]diazepin‐1‐ones, highly regioselective benzimidazole derivatives and derivatives of quinoxalines. Operational simplicity, mild reaction conditions, shorter reaction times, and use of green solvents are the highlights of this protocol. The advantage of ultrasonic irradiation has been significantly explored for the synthesis of the aforesaid compounds. Furthermore, the multifaceted use of o‐phenylenediamine has also been accentuated in the study. 相似文献
38.
Kriti Pathak Sourav Gayen Suvam Saha Chandan Nandi Shivankan Mishra Prof. Dr. Sundargopal Ghosh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(18):e202104393
Treatment of [Cp*RuCl2]2, 1 , [(COD)IrCl]2, 2 or [(p-cymene)RuCl2]2, 3 (Cp*=η5-C5Me5, COD= 1,5-cyclooctadiene and p-cymene=η6-iPrC6H4Me) with heterocyclic borate ligands [Na[(H3B)L], L1 and L2 ( L1 : L=amt, L2 : L=mp; amt=2-amino-5-mercapto-1,3,4-thiadiazole, mp=2-mercaptopyridine) led to the formation of borate complexes having uncommon coordination. For example, complexes 1 and 2 on reaction with L1 and L2 afforded dihydridoborate species [LAM(μ-H)2BHL] 4 – 6 ( 4 : LA=Cp*, M=Ru, L=amt; 5 : LA=Cp*, M=Ru, L=mp; 6 : LA=COD, M=Ir, L=mp). On the other hand, treatment of 3 with L2 yielded cis- and trans-bis(dihydridoborate) species, [Ru{(μ-H)2BH(mp)}2], cis- 7 and trans- 7 . The isolation and structural characterization of fac- and mer-[Ru{(μ-H)2BH(mp)}{(μ-H)BH(mp)2}], 8 from the same reaction offered an insight into the behaviour of these dihydridoborate species in solution. Fascinatingly, despite having reduced natural charges on Ru centres both at cis-and trans- 7 , they underwent hydroboration reaction with alkynes that yielded both Markovnikov and anti-Markovnikov addition products, 10 a – d . 相似文献
39.
Structural Chemistry - The N-methyl-D-aspartate (NMDA) is the family of glutamate receptor, which is involved in controlling synaptic plasticity and memory function; but overactivation of this... 相似文献
40.
G. Benz H. Lüers P. Bohrisch M. Tortelli R. Ruggeri W. Otte E. Kröger W. Lühr H. Schmalfuß H. Werner R. Strohecker J. Großfeld A. Beckel H. Thaler K. Täufel K. Richter H. Damm E. Ruppol H. A. A. Aitken R. Delaby Yvonne Breugnot S. F. Juschkewitsch N. M. Ssokolow P. Arup J. T. Minster 《Analytical and bioanalytical chemistry》1933,94(7-8):286-295