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161.
Nonlinear Dynamics - In this paper, we introduce a SEIATR compartmental model to analyze and predict the COVID-19 outbreak in the Top 5 affected countries in the world, namely the USA, India,... 相似文献
162.
Mohammad Zaman Kassaee Farnaz Alipour Shakib Mohammad Reza Momeni Mehdi Ghambarian Seyed Majid Musavi 《Monatshefte für Chemie / Chemical Monthly》2009,9(4):33-38
Abstract
Based on geometries and relative energies, three different mechanisms are proposed for the rearrangements of five isomers of silacyclohexadienylidenes to silabenzene at B3LYP and MP2 levels: (1) [1,2]-hydrogen migration through a planar transition state, (2) [1,4]-hydrogen migration through a boat transition state, and (3) zip-zap mechanism, comprised of three successive [1,2]-hydrogen migrations. The above results are compared and contrasted to rearrangements of the corresponding cyclohexadienylidenes to benzene. 相似文献163.
164.
An analytical formulation is developed to predict the flexural behavior of a cylindrical liquid storage tank resting on an isotropic elastic soil medium, which is modelled as a half space. The interface between the plate foundation and the soil medium is considered to be smooth and continuous. The plate deflection function is assumed in the form of a power series expansion in terms of the radial coordinate. The procedure accounts for the interactions between the tank wall and the plate foundation, and between the plate foundation and the soil medium. The principle of minimum potential energy is used to evaluate the unknown coefficients appearing in the assumed power series expansion and also the unknown interacting forces at the tank wall-plate foundation junction. Any number of terms can be considered in the assumed deflection function. Analytical expressions are obtained for the plate foundation deflections and radial moment, the contact stress distribution, the tank wall displacements, and the tank wall stress resultants. The results obtained compare well with the finite element analysis of a similar problem. Results of a parametric study are also presented to demonstrate the effect of the various geometric and material parameters on the flexural behavior of the system. 相似文献
165.
M. R. Zaman 《Journal of Radioanalytical and Nuclear Chemistry》1995,199(1):15-19
Reactions between aniline and dibromomethane (DBM) or 1,2-dibromoethane (DBE) produce fine glassy crystals at ordinary temperature. Due to these product formation processes, aniline fails to exert its scavenging action on bromine recoil reactions in these media. 相似文献
166.
In this paper, we consider a Holling type model, which describes the interaction between two preys with a common predator. First, we give some sufficient conditions for the globally asymptotic stability and prove that local stability implies global stability. Then, we present a set of sufficient conditions for the existence of a positive periodic solution with strictly positive components. Finally, the optimal control strategy is developed to minimize the number of predator and maximize the number of preys. We also show the existence of an optimal control for the optimal control problem and derive the optimality system. The technical tool used to determine the optimal strategy is the Pontryagin Maximum Principle. Finally, the numerical simulations of global stability and the optimal problem are given as the conclusion of this paper. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
167.
Nisar Ali ;Baoliang Zhang ;Hepeng Zhang ;Wajed Zaman ;Wei Li ;Qiuyu Zhang 《Particuology》2014,(6):59-65
Inorganic/organic poly(methylmethacrylate-acrylic acid-divinylbenzene) iron oxide Janus magnetic nanoparticles(P(MMA-AA-DVB)/Fe3O4) with strong magnetic domains and unique surface functionalities were prepared using a solvothermal process.The P(MMA-AA-DVB) nanoparticles were prepared via soapfree emulsion polymerization and used as a precursor for preparing Janus nanoparticles.The morphology and magnetic properties of the magnetic Janus nanoparticles formed were characterized using a laser particle size analyzer,transmission electron microscopy,Fourier transform infrared spectroscopy,vibrating sample magnetometry,and thermogravimetric analysis.The synthesized P(MMA-AA-DVB)/Fe3O4 magnetic Janus nanoparticles were characterized by a Janus structure and possessed a stable asymmetric morphology after being dually functionalized.The particle size,magnetic content,and magnetic domain of the P(MMA-AA-DVB)/Fe3O4 magnetic Janus nanoparticles were 200 nm,40%,and 25 emu/g,respectively.The formation mechanism of the Janus nanoparticles was also investigated,and the results revealed that the reduction of Fe3+ ions and growth of Fe3O4 took place on the surface of the P(MMA-AA-DVB) polymeric precursor particles.The size of the Janus particles could be controlled by narrowing the size distribution of the P(MMA-AA-DVB) precursor nanoparticles. 相似文献
168.
Bibi Narjes Haerizade Mohammad Zaman Kassaee Hassan Zandi Maryam Koohi Ali A. Ahmadi 《Journal of Physical Organic Chemistry》2014,27(11):902-908
High‐level Density Functional Theory calculations, coupled with appropriate isodesmic reaction, are employed to investigate the effects of α‐carbon, ammonium, phosphorus, and sulfur ylides, cyclization, and unsaturation on the stability, multiplicity, and reactivity of novel singlet (S) and triplet (T) carbenes. Among them the highly π‐donating α‐ammonium ylide is found to exert the highest stabilizing effect on the carbenic center. α‐Ammonium ylides resist dimerization and hydrogenation. They show wider singlet–triplet energy gap (ΔΕS–T), broader band gap (ΔΕHOMO–LUMO), and higher nucleophilicity compared to the reported stable N‐heterocyclic carbenes. Aromatic cyclic unsaturated ammonium, phosphorus, and sulfur ylide carbenes appear more stable than their saturated cyclic analogs which are in turn more viable than their acyclic counterparts. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
169.
Naik H. Kim G. N. Kim K. Zaman M. Sahid M. Yang S. -C. Lee M. W. Kang Y. R. Shin S. G. Cho M. -H. Goswami A. Song T. Y. 《The European Physical Journal A - Hadrons and Nuclei》2014,50(7):1-13
We investigate the parity-violating nucleon-nucleon potential as obtained in chiral effective field theory. By using resonance saturation we compare the chiral potential to the more traditional one-meson-exchange potential. In particular, we show how parameters appearing in the different approaches can be compared with each other and demonstrate that analyses of parity violation in proton-proton scattering within the different approaches are in good agreement. In the second part of this work, we extend the parity-violating potential to next-to-next-to-leading order. We show that generally it includes both one-pion- and two-pion-exchange corrections, but the former play no significant role. The two-pion-exchange corrections depend on five new low-energy constants which only become important if the leading-order weak pion-nucleon constant h π turns out to be very small. 相似文献
170.
Mohammad Zaman Kassaee Maryam Koohi Reza Mohammadi Monireh Ghavami 《Journal of Physical Organic Chemistry》2013,26(11):908-916
Replacement of α‐methylenes with BH, AlH, CMe2, SiH2, NH, NMe, NtButyl, NPh, PH, O, and S in non‐planar cyclonona‐3,5,7‐trienylidene (CH2) alters its status from an unstable transition state to rather stable minima, at B3LYP/6‐311++G**//B3LYP/6‐31 + G* levels of theory. All species appear with singlet closed shell (Scs) global minima, except for SiH2 and CH2 which exhibit triplet electronic ground states. The order of stability based on singlet–triplet energy gap (ΔEs–t / kcalmol?1) is: CMe2 (45.8) > NH (35.8) > NMe (32.3) > O (31.5) > NtButyl (27.7) ≥ NPh (27.5) ≥ BH (27.4) > S (21.9) > PH (17.0) > CH2 (?4.4) > SiH2 (?12.5). In contrast to many reports on N‐heterocyclic carbenes, here alkyl groups appear to exert a higher stabilizing effect than heteroatoms, making CMe2 the most stable. In addition bulky NMe, NtButyl, and NPh appear more nucleophilic than their synthesized imidazol‐2‐ylidene congeners. Excluding SiH2, isodesmic reactions reveal that all substituents stabilize singlet state considerably more than the corresponding triplet. Finally, this work is hoped to pave the path for future matrix isolations and IR studies of these rather stable cyclic non‐planar carbenes. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献