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D. M. Petrović-Djakov J. M. Filipović Lj. P. Vrhovac J. S. Veličković 《Journal of Thermal Analysis and Calorimetry》1996,46(6):1681-1686
The kinetics of the AIBN-initiated free radical bulk polymerization of fiveo-alkylphenyl methacrylates was studied by means of DSC in the temperature range 353–373 K, and the enthalpy of polymerization, the overall reaction rate constant and the activation energy were determined. The results were compared with those published recently on correspondingp-alkylaryl methacrylates. All measured reaction rate constants were found to increase with increasing temperature and to decrease with increasingo-alkyl substituent mass and size. It was shown thato-substituents influence the rates of polymerization to a greater extent thanp-substituents. At about 373 K, all differences in rate, most probably resulting from steric hindrance caused by the alkyl groups, disappear in both series, a phenomenon earlier observed for dimethyl phenyl methacrylates.This work was supported by the Ministry of Science of the Republic of Serbia. 相似文献
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J.V. Jovanović S.B. Vrhovac Z.Lj. Petrović 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(3):335-342
Transport properties of ion swarms in presence of Resonant Charge Transfer (RCT) collisions are studied using Momentum Transfer
Theory (MTT). It was shown that, not surprisingly, RCT collisions may be represented as a special case of elastic scattering.
Using the developed MTT we tested a previously available anisotropic set of cross-sections for Ar+Ar
+ collisions by making the comparisons with the available data for the transverse diffusion coefficient. We also developed
an anisotropic set of Ne+Ne
+ integral cross-sections based on the available data for mobility, longitudinal and transverse diffusion. Anisotropic sets
of cross-sections are needed for Monte Carlo simulations of ion transport and plasma models.
Received 16 June 2002 / Received in final form 2nd August 2002 Published online 24 September 2002
RID="a"
ID="a"e-mail: vrhovac@phy.bg.ac.yu
RID="b"
ID="b"e-mail: zoran@phy.bg.ac.yu 相似文献
4.
Overtone spectrum of o, m and p-nitrobenzaldehydes and p-chlorobenzaldehyde has been studied in 2000–12000 cm−1 region. Vibrational frequencies and anharmonicity constants for aryl as well as alkyl CH stretch vibrations have been determined.
We have also determined the internuclear distances for the aryl CH bond in the different molecules. The small variation observed
in these distances is an indication of the substitution effect.
It is observed that in the case of p-disubstituted benzens, the shift in aryl CH bond is proportional to sum of the Hammet σ of the substituents. However in the
case of o-disubstituted benzenes it is only 80% of the para-substituted shift. 相似文献
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J. M. Filipovic D. M. Petrovic-Djakov Lj. P. Vrhovac J. S. Velickovic 《Journal of Thermal Analysis and Calorimetry》1993,40(2):735-740
The free radical copolymerization of phenyl methacrylate (PhMA) witho-methylphenyl-methacrylate(o-MPhMA) ando-ethylphenyl methacrylate (o-EPhMA) was carried out and the enthalpies of copolymerization, overall rate constants and copolymerization parameters were determined for different molar ratios of comonomers in the temperature range 353–373 K. 相似文献
7.
With the advent of medium and large gamma detector arrays, it is now possible to look at nuclear structure at high rotational
forces. The role of pairing correlations and their eventual breakdown, along with the shell effects have showed us the interesting
physics for nuclei at high spins — superdeformation, shape co-existence, yrast traps, alignments and their dramatic effects
on nuclear structure and so on. Nuclear structure studies have recently become even more exciting, due to efforts and possibilities
to reach nuclei far off from the stability valley. Coupling of gamma ray arrays with ‘filters’, like neutron wall, charged
particle detector array, gamma ray total energy and multiplicity castles, conversion electron spectrometers etc gives a great
handle to study nuclei produced online with ‘low’ cross-sections. Recently we studied, nuclei in mass region 80 using an array
of 8 germanium detectors in conjunction with the recoil mass analyser, HIRA at the Nuclear Science Centre and, most unexpectedly
came across the phenomenon of identical bands, with two quasi-particle difference. The discovery of magnetic rotation is another
highlight. Our study of light In nucleus, 107In brought us face to face with the ‘dipole’ bands. I plan to discuss some of
these aspects. There is also an immensely important development — that of the ‘radioactive ion beams’. The availability of
RIB, will probably very dramatically influence our ‘conventional’ concept of nuclear structure. The exotic shapes of these
exotic nuclei and some of their expected properties will also be touched upon. 相似文献
8.
Rare earth element substituted bismuth ferrites (BiFeO3) are of enormous importance as magnetoelectric materials. The polycrystalline samples of Bi
x
La1−x
FeO3 (x=0, 0.2, 0.4, 0.6, 0.8) were prepared by solid-state reaction using standard ceramic method. The single-phase formation of
these compounds was confirmed by X-ray diffraction (XRD) studies. The samples with x=0, 0.2, 0.4, 0.6 are found to be orthorhombic while the sample with x=0.8 is triclinic. The dielectric constant (ε′) and dissipation factor (tan δ) were measured in the frequency range 100 Hz
to 1 MHz at room temperature and as a function of temperature at certain fixed frequencies (1 kHz, 10 kHz, 100 kHz, 1 MHz).
All the samples showed dielectric dispersion. The dielectric constant with temperature shows a broad peak; the peak temperature
shifts with frequency which reflects the relaxor-type behavior. The peak above 600 K in the measured temperature range corresponds
to antiferromagnetic ordering temperature (Néel temperature). The broadness of the peak changes with composition. The ac conductivity
as well as ε′ are found to be maximum for the sample x=0.2 at room temperature. 相似文献
9.
Loncarević I Budinski-Petković Lj Vrhovac SB 《The European physical journal. E, Soft matter》2007,24(1):19-26
Random sequential adsorption of binary mixtures of extended objects on a two-dimensional triangular lattice is studied numerically
by means of Monte Carlo simulations. The depositing objects are formed by self-avoiding random walks on the lattice. We concentrate
here on the influence of the symmetry properties of the shapes on the kinetics of the deposition processes in two-component
mixtures. Approach to the jamming limit in the case of mixtures is found to be exponential, of the form: θ(t) ∼ θjam - Δθ exp(- t/σ), and the values of the parameter σ are determined by the order of symmetry of the less symmetric object in the mixture.
Depending on the local geometry of the objects making the mixture, jamming coverage of a mixture can be either greater than
both single-component jamming coverages or it can be in between these values. Results of the simulations for various fractional
concentrations of the objects in the mixture are also presented. 相似文献
10.
I.?Lon?arevi? Z. M.?Jak?i? S. B.?Vrhovac Lj.?Budinski-Petkovi? 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,73(3):439-445
Random sequential adsorption with diffusional relaxation of extended objects
both on a one-dimensional and planar triangular lattice is studied numerically
by means of Monte Carlo simulations. We focus our attention on the behavior of
the coverage θ(t) as a function of time. Our results indicate that the
lattice dimensionality plays an important role in the present model.
For deposition of k-mers on 1D lattice with diffusional relaxation, we found
that the growth of the coverage θ(t) above the jamming limit to the
closest packing limit θCPL is described by the pattern
θCPL-θ(t) ∝Eβ[-(t/τ)β], where Eβ
denotes the Mittag-Leffler function of order β∈(0,1). In the case of
deposition of extended lattice shapes in 2D, we found that after the initial
“jamming", a stretched exponential growth of the coverage θ(t) towards
the closest packing limit θCPL occurs, i.e., θCPL -
θ(t) ∝exp [-(t/τ)β]. For both cases we observe that: (i)
dependence of the relaxation time τ on the diffusion probability Pdif
is consistent with a simple power-law, i.e., τ∝Pdif
-δ;
(ii) parameter β depends on the object size in 1D and on the particle
shape in 2D. 相似文献