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41.
Zorica M. Bugarčić Biljana Mojsilović Ljiljana Marjanović Stanimir Konstantinović 《Monatshefte für Chemie / Chemical Monthly》2000,131(10):1091-1096
Summary. The reaction of some alkenols with tetrachloromethane in the presence of a radical initiator was investigated. Regarding
the effects of structural features of the starting alkenol (number and position of methyl substituents at the double bond
and at the carbinol carbon atom, constitutional relationship between the double bond and the hydroxyl group) there are two
possible competing reactions: addition and cyclization. In the case of the simplest alkenols (without substituents and with
a more remote double bond) addition occurs; mono- and disubstituted secondary and tertiary Δ4- and Δ5-alkenols cyclize in high yields to give the corresponding cyclic ethers.
Received March 17, 2000. Accepted (revised) May 31, 2000 相似文献
42.
In this study, the methodology developed by Srdjevic and Cveticanin (International Journal of Industrial Ergonomics 34 (2004) 307–318) for the nonbiased (objective) parameter identification of the linear biomechanical model exposed to vertical vibrations is extended to the identification of n-degree of freedom (DOF) nonlinear biomechanical models. The dynamic performance of the n-DOF nonlinear model is described in terms of response functions in the frequency domain, such as the driving-point mechanical impedance and seat-to-head transmissibility function. For randomly generated parameters of the model, nonlinear equations of motion are solved using the Runge–Kutta method. The appropriate data transformation from the time-to-frequency domain is performed by a discrete Fourier transformation. Squared deviations of the response functions from the target values are used as the model performance evaluation criteria, thus shifting the problem into the multicriteria framework. The objective weights of criteria are obtained by applying the Shannon entropy concept. The suggested methodology is programmed in Pascal and tested on a 4-DOF nonlinear lumped parameter biomechanical model. The identification process over the 2000 generated sets of parameters lasts less than 20 s. The model response obtained with the imbedded identified parameters correlates well with the target values, therefore, justifying the use of the underlying concept and the mathematical instruments and numerical tools applied. It should be noted that the identified nonlinear model has an improved accuracy of the biomechanical response compared to the accuracy of a linear model. 相似文献
43.
Teodor M. Atanackovic Stevan Pilipovic Dusan Zorica 《Continuum Mechanics and Thermodynamics》2011,23(4):305-318
We study waves in a rod of finite length with a viscoelastic constitutive equation of distributed fractional order type for
the special choice of weight functions. Prescribing boundary conditions on displacement and stress, we obtain, as special
solutions, cases corresponding to creep and forced oscillations. In solving system of differential and integro-differential
equations, we use the Laplace transformation in the time domain. 相似文献
44.
45.
An experimental design method was used for fast, simple, and accurate high-performance-pressure liquid chromatograpy (HPLC) determination of losartan and hydrochlorothiazide in combined dosage forms. This method avoids the disadvantages of the traditional analytical approach, which is time-consuming, involves a large number of runs, and does not allow the determination of multiple interacting parameters. On the basis of preliminary experiments, three independent variables (methanol content, pH value of the mobile phase, and flow rate) were selected as input, and as dependent variables, five responses (retention time of hydrochlorothiazide, retention time of losartan, asymmetry of hydrochlorothiazide peak, asymmetry of losartan peak, and resolution) were chosen. A full 23 factorial design was used to determine which factors had an effect on the studied response. Afterwards, experimental design was used to optimize these influencing parameters in the previously selected experimental domain. After optimizing the experimental conditions, a separation was conducted on a Zorbax C8 (150 mm × 4.6 mm, 5 μm particle size) column with a mobile phase consisting of methanol–acetonitrile–acetate buffer 45:20:35 v/v/v, pH 4.8 with flow rate of 0.82 mL min?1 and column temperature of 25 °C. The developed method was successfully applied to simultaneous separation of these active drug compounds in their commercial pharmaceutical dosage forms. 相似文献
46.
Jovana?Mu?kinja Nenad?Jankovi?Email author Zoran?Ratkovi? Goran?Bogdanovi? Zorica?Bugar?i? 《Molecular diversity》2016,20(3):591-604
A small library of novel 2-oxo-1,2,3,4-tetrahydropyrimidines was synthesized via a one-pot multicomponent Biginelli reaction. Copper complex \((\hbox {PhNH}_{3})_{2}\hbox {CuCl}_{4,}\) which was used for the first time as a homogeneous and heterogeneous catalyst, makes this a facile and efficient reaction at room temperature. All the obtained products fall out of the solution in pure form and are easily isolated via filtration in good-to-excellent yields. The molecular structure of one of the products, ethyl 6-methyl-2-oxo-4-(4\(^\prime \)-isopropoxy-3\(^\prime \)-methoxyphenyl) - 1,2,3,4 - tetrahydropyrimidine-5- carboxylate, has been determined by X-ray crystallography. All non-hydrogen atoms in the heterocyclic, six-membered ring are determined to be approximately coplanar. 相似文献
47.
This paper considers a recently introduced NP-hard problem on graphs, called the dominating tree problem. In order to solve this problem, we develop a variable neighborhood search (VNS) based heuristic. Feasible solutions are obtained by using the set of vertex permutations that allow us to implement standard neighborhood structures and the appropriate local search procedure. Computational experiments include two classes of randomly generated test instances and benchmark test instances from the literature. Optimality of VNS solutions on small size instances is verified with CPLEX. 相似文献
48.
Petrović ZD Petrović VP Simijonović D Marković S 《Dalton transactions (Cambridge, England : 2003)》2011,40(36):9284-9288
The reaction of K(2)PtCl(4) with the alkylating agent mechlorethamine hydrochloride, at a molar ratio of 1:2, results in the formation of 2-chloro-N-(2-chloroethyl)-N-methylethylammonium-tetrachloridoplatinate(II) complex. The hydrolytic activity of the novel Pt(II) complex was tested in the reaction with N-acetylated L-histidylglycine dipeptide at a molar ratio 1:1. It was shown that the hydrolytic reaction, performed at 60 °C in acidic medium, leads to the regioselective cleavage of the amide bond involving the carboxylic group of histidine. Density functional theory was used to explore the structures of the proposed participants in the hydrolytic reaction. 相似文献
49.
Željka Jovanović Aleksandra Radosavljević Milorad Šiljegović Nataša Bibić Vesna Mišković-Stanković Zorica Kačarević-Popović 《Radiation Physics and Chemistry》2012,81(11):1720-1728
Silver nanoparticles (AgNPs) were synthesized in situ by γ-irradiation using poly(N-vinyl-2-pyrrolidone) (PVP) as a capping agent. The concentration, molecular weight and the structure (crosslinked and interpenetrated network) of PVP were varied, in order to determine the influence of the capping agent in the radiolytic synthesis of the Ag/PVP nanosystems. Transmission electron microscopy (TEM) showed that AgNPs obtained from the solutions containing higher PVP concentration and higher molecular weight were spherical in shape, with narrow size distribution and a diameter of~6 nm, while slightly larger rod-shaped silver agglomerates, with bimodal nanoparticle size distribution and diameters of ~10 nm and ~20 nm were obtained from the solutions containing lower PVP concentration and lower molecular weight. Strong plasmon coupling and extending of plasmon resonance was observed by UV–vis spectroscopy, as a result of formation of nanorod-like agglomerates. Crosslinked and interpenetrated network did not affect the structure of synthesized AgNPs. Ag/PVP nanocomposite, in the form of thin film, was obtained by solvent evaporation from Ag/PVP colloid solution with 10 wt% of PVP, and characterized by FTIR spectroscopy. The interactions in Ag/PVP nanocomposite are shown to be the result of the coordination bonding between AgNPs and nitrogen from pyrrolidone ring of PVP. The optical properties of investigated Ag/PVP nanosystems, as measured by the values of optical band gap, Eg, are mainly the consequence of the interparticle distance as a result of the concentration and the structure of surrounding PVP macromolecules. 相似文献
50.
Teodor Atanackovi? Sanja Konjik Ljubica Oparnica Du?an Zorica 《Continuum Mechanics and Thermodynamics》2012,24(4-6):293-311
The classical heat conduction equation is generalized using a generalized heat conduction law. In particular, we use the space-time Cattaneo heat conduction law that contains the Caputo symmetrized fractional derivative instead of gradient ${{\partial_x}}$ and fractional time derivative instead of the first order partial time derivative ${{\partial_t}}$ . The existence of the unique solution to the initial-boundary value problem corresponding to the generalized model is established in the space of distributions. We also obtain explicit form of the solution and compare it numerically with some limiting cases. 相似文献