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排序方式: 共有239条查询结果,搜索用时 31 毫秒
111.
M. Karami M. Raisee S. Delfani M. A. Akhavan Bahabadi A. M. Rashidi 《Optics and Spectroscopy》2013,115(3):400-405
Solar thermal collectors are applicable in the water heating or space conditioning systems in which surface-based absorption of incident solar flux cause high heat losses. Therefore, an enhancement in the efficiency of solar harvesting devices is a basic challenge which requires great effort. Adding nanoparticles to the working fluid in direct absorption solar collector, which has been recently proposed, leads to improvement in the working fluid thermal and optical properties such as thermal conductivity and absorption coefficient. This results certainly in collector efficiency enhancement. In this paper, the characteristics of nanofluids consisting carbon nanoball in water- and ethylene glycol-based suspensions in consideration of their use as sunlight absorber fluid in a DASC are investigated. It was found that by using of 300 ppm carbon nanoballs, the extinction coefficient of pure water and ethylene glycol is increased by about 3.9 cm?1 and 3.4 cm?1 in average, respectively. With these significantly promising optical properties, a direct absorption solar collector using carbon nanoball-based nanofluids can achieve relatively higher efficiencies, compared with a conventional solar collector. 相似文献
112.
The probability density function plays an essential role to investigate the behaviors of stochastic linear or nonlinear systems. This function can be evaluated by several approaches but due to its analytical theme, the Fokker–Planck–Kolmlgorov (FPK) approach is preferable. FPK equation is a nonlinear PDE gives the probability density function for a stochastic linear or nonlinear system. Many researches have been done in literature tried to specify the conditions, in which the FPK equation gives an exact solution. Although, the exact probability density function can be achieved by solving the FPK equation even for some nonlinear systems, many types of systems cannot satisfy the conditions for exact solution. In this article, the axially moving viscoelastic plates under both external and parametric white noise excitation as one of the newest and applicable research areas are studied. Due to strong nonlinearities recognized in the governing equation of the system, the exact probability density function cannot be obtained, however, via an approximate method; some precise approximate solutions for different but comprehensive case studies are evaluated, validated, and discussed. 相似文献
113.
Zahra Haghighi Amir-Hossein Karimy Farshad Karami Mohammadreza Khanmohammadi 《Natural product research》2019,33(7):1052-1060
AbstractThis paper addresses the application of infrared spectroscopy in combination with chemometrics to identify wall painting’s binding medium while employing pattern recognition techniques to process FTIR data-set of complex samples. In this regard, based on the historical documents and previous researches, firstly 56 standard samples were prepared to represent strata of Persian wall paintings in the Safavid period in addition to real historic samples from the case study; Sukias mansion. Then, each sample was analysed by the means of FTIR and chemometrics. Finally, SIMCA was applied to the whole region of studied IR spectra which predicted egg yolk as the binding medium of Sukias mansion samples. 相似文献
114.
Molecular Diversity - Herein, an effectual, quick and novel method is described for the synthesis of new triazolo[1,5-a]pyrimidine, triazolo[5,1-b][1,3] thiazine and pyrazolo[1,5-a]pyrimidine... 相似文献
115.
116.
Karami M. Safaei M. Shishehbore M. R. Sheibani A. 《Journal of Applied Spectroscopy》2021,88(5):1095-1104
Journal of Applied Spectroscopy - A new, accurate, sensitive, and reliable kinetic spectrophotometric method for the determination of vitamin B12 in biological samples and pharmaceutical... 相似文献
117.
A set S of vertices of a graph G = (V, E) without isolated vertex is a total dominating set if every vertex of V(G) is adjacent to some vertex in S. The total domination number γ
t
(G) is the minimum cardinality of a total dominating set of G. The total domination subdivision number
is the minimum number of edges that must be subdivided (each edge in G can be subdivided at most once) in order to increase the total domination number. In this paper we prove that for every simple
connected graph G of order n ≥ 3,
where d
2(v) is the number of vertices of G at distance 2 from v.
R. Khoeilar: Research supported by the Research Office of Azarbaijan University of Tarbiat Moallem. 相似文献
118.
A Roman dominating function of a graph G is a labeling f:V(G)?{0,1,2} such that every vertex with label 0 has a neighbor with label 2. The Roman domination number γR(G) of G is the minimum of ∑v∈V(G)f(v) over such functions. A Roman dominating function of G of weight γR(G) is called a γR(G)-function. A Roman dominating function f:V?{0,1,2} can be represented by the ordered partition (V0,V1,V2) of V, where Vi={v∈V∣f(v)=i}. Cockayne et al. [E.J. Cockayne, P.A. Dreyer, S.M. Hedetniemi, S.T. Hedetniemi, On Roman domination in graphs, Discrete Math. 278 (2004) 11-22] posed the following question: What can we say about the minimum and maximum values of |V0|,|V1|,|V2| for a γR-function f=(V0,V1,V2) of a graph G? In this paper we first show that for any connected graph G of order n≥3, , where γ(G) is the domination number of G. Also we prove that for any γR-function f=(V0,V1,V2) of a connected graph G of order n≥3, , and . 相似文献
119.
Reza Rashidi Ardeshir Karami mohammadi Firooz Bakhtiari nejad 《Nonlinear dynamics》2010,60(3):231-253
This paper presents the effect of preload, as one of the design parameters, on nonlinear dynamic behavior of a rigid rotor
supported by gas-lubricated noncircular journal bearings. A finite element method has been employed to solve the Reynolds
equation in static and dynamical states and the dynamical equations are solved using the Runge–Kutta method. To analyze the
behavior of the rotor center in horizontal and vertical directions under different operating conditions, dynamic trajectory,
power spectra, Poincare maps, and bifurcation diagrams are used. Results of this study reveal how the complex dynamic behavior
of two types of noncircular bearing systems comprising periodic, KT-periodic, and quasi-periodic responses of the rotor center varies with changes in preload value. 相似文献
120.
In this study, the immobilization of sulfonic acid on silica‐layered magnetite was carried out by the reaction of ClSO3H with silica‐layered magnetite. The prepared magnetic nanoparticles of Fe3O4@SiO2‐SO3H were then characterized using scanning electron microscopy, energy dispersive X‐ray spectroscopy, X‐ray diffraction, Fourier transform infrared spectroscopy, vibrating sample magnetometry, and transmission electron microscopy. The sulfonated nanocomposite exhibited excellent catalytic activity and reusability in the reduction of various aldoximes and ketoximes with NaBH3CN in the presence of ZrCl4. All reactions were carried out under solvent‐free conditions (r.t. or 75–80°C) within 3–70 min to afford amines in high to excellent yields. 相似文献