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排序方式: 共有90条查询结果,搜索用时 31 毫秒
21.
Xu M Larentzos JP Roshdy M Criscenti LJ Allen HC 《Physical chemistry chemical physics : PCCP》2008,10(32):4793-4801
Nitrate aqueous solutions, Mg(NO(3))(2), Ca(NO(3))(2), Sr(NO(3))(2), and Pb(NO(3))(2), are investigated using Raman spectroscopy and free energy profiles from molecular dynamics (MD) simulations. Analysis of the in-plane deformation, symmetric stretch, and asymmetric stretch vibrational modes of the nitrate ions reveal perturbation caused by the metal cations and hydrating water molecules. Results show that Pb(2+) has a strong tendency to form contact ion pairs with nitrate relative to Sr(2+), Ca(2+), and Mg(2+), and contact ion pair formation decreases with decreasing cation size and increasing cation charge density: Pb(2+) > Sr(2+) > Ca(2+) > Mg(2+). In the case of Mg(2+), the Mg(2+)-OH(2) intermolecular modes indicate strong hydration by water molecules and no contact ion pairing with nitrate. Free energy profiles provide evidence for the experimentally observed trend and clarification between solvent-separated, solvent-shared, and contact ion pairs, particularly for Mg(2+) relative to other cations. 相似文献
22.
Albayari Mohammad Nazal Mazen K. Khalili Fawwaz I. Nordin Norazzizi Adnan Rohana 《Journal of Radioanalytical and Nuclear Chemistry》2021,328(2):669-678
Journal of Radioanalytical and Nuclear Chemistry - In recent years, biochar based adsorbents have been given more attention for organic and inorganic pollutants removal. Therefore, in this study, a... 相似文献
23.
We use asymptotically optimal adaptive numerical methods (here specifically a wavelet scheme) for snapshot computations within the offline phase of the Reduced Basis Method (RBM). The resulting discretizations for each snapshot (i.e., parameter-dependent) do not permit the standard RB ‘truth space’, but allow for error estimation of the RB approximation with respect to the exact solution of the considered parameterized partial differential equation. The residual-based a posteriori error estimators are computed by an adaptive dual wavelet expansion, which allows us to compute a surrogate of the dual norm of the residual. The resulting adaptive RBM is analyzed. We show the convergence of the resulting adaptive greedy method. Numerical experiments for stationary and instationary problems underline the potential of this approach. 相似文献
24.
Microstructure, electrical, mechanical and thermal properties of quenched bismuth–tin eutectic, Rose (Bi50Sn22.9Pb27.1) and Wood’s (Bi50Sn12.5Pb25Cd12.5) alloys have been investigated using scanning electron microscopy, X-ray diffraction analysis, the double bridge method, the dynamic resonance method, Vickers hardness measurement and thermal analysis. Wood’s alloy (Bi–Pb–Sn–Cd) has low electrical resistivity and melting point but a high elastic modulus and internal friction when compared with the Rose (Bi–Pb–Sn) alloy. The presence of cadmium in Wood’s alloy decreases its melting point and electrical resistivity with an increase in its elastic modulus, which improves the mechanical properties. Wood’s alloy (Bi–Pb–Sn–Cd) has better properties, which make it useful in various applications such as in protection shields for radiotherapy, locking of mechanical devices and welding at low temperature. 相似文献
25.
Ahmad Al Hanbali 《Queueing Systems》2011,67(3):221-249
In this paper, we study the transient behavior of a level dependent single server queuing system with a waiting room of finite
size during the busy period. The focus is on the level dependent PH/PH/1/K queue. We derive in closed form the joint transform
of the length of the busy period, the number of customers served during the busy period, and the number of losses during the
busy period. We differentiate between two types of losses: the overflow losses that are due to a full queue and the losses
due to an admission controller. For the M/PH/1/K, M/PH/1/K under a threshold policy, and PH/M/1/K queues, we determine simple
expressions for their joint transforms. 相似文献
26.
de Meijere A Korotkov VS Lygin AV Larionov OV Sokolov VV Graef T Es-Sayed M 《Organic & biomolecular chemistry》2012,10(31):6363-6374
Successful biochemical studies of the natural products belactosin A and C and their acylated congeners have shown a β-lactonecarboxamide moiety to be a possible core structure of powerful proteasome inhibitors. As a part of further investigations, variously decorated simplified β-lactonecarboxamides have been synthesized in order to understand structure-biological activity relations in detail, to find ways of improving their biological activity and stability and to reduce the complexity of their preparation. Biological tests showed that the best compounds possess a high potential against phytopathogenic fungi in the greenhouse. 相似文献
27.
In this paper, the cut-off bit-pattern phenomenon of a digitally-modulated semiconductor laser diode (LD) is calculated. The cut-off bit-pattern $\left( {Q_{\textit{off}}^{\textit{cut}\text{- }\textit{off}} }\, \right) $ Q off cut - off is defined as the number of “0” bits (i.e., OFF pulses) preceding the considered “1” bit (i.e., ON pulse) above which an LD cannot respond normally to an injected data pattern and will consequently shutdown or become inoperable. The latter case occurs when the turn-on time delay of an LD exceeds the bit-time interval of the injected current pulse. An analytical calculation for an LD’s cut-off bit-pattern is derived in terms of laser cavity parameters, bit rate, modulation and dc-bias currents. This calculation can be used to predetermine, based on typical values for an LD, accurate dc-bias and modulation current values that should be utilized to ensure an LD is operational for high-speed optical communications applications. 相似文献
28.
Mazen Bou Khuzam 《Geometriae Dedicata》2013,163(1):45-59
A Knot ${K\subset S^{3}}$ is said to satisfy the G-property if for every ${r \in \mathbb{Q}}$ the manifold M(K, r) obtained by rational surgery on K with surgery coefficient r is the boundary of a Stein domain. The problem of finding which knots satisfy the G-property is still wide open. This paper introduces this problem and presents some techniques used to prove that certain infinite families of knots satisfy the G-property. 相似文献
29.
In this paper we analyze the interval availability of a two-echelon, multi-item spare part inventory system. We consider a scenario inspired by a situation that we encountered at Thales Netherlands, a manufacturer of naval sensors and naval command and control systems. Modeling the complete system as a Markov chain we analyze the interval availability and we compute in closed and exact form the expectation and the variance of the availability during a finite time interval [0, T]. We use these characteristics to approximate the survival function using a Beta distribution, together with the probability that the interval availability is equal to one. Comparison of our approximation with simulation shows excellent accuracy, especially for points of the distribution function below the mean value. The latter points are practically most relevant. 相似文献
30.