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•New thermosensitive star-shaped four-arm poly-2-ethyl-2-oxazine was synthesized.•In organic solvent the arms of star-shaped polymers have a folded conformation.•At room temperature, ...aqueous solutions of the star were not molecularly dispersed.•At low temperatures, isolated macromolecules prevailed in star aqueous solutions.•LCST for a star-shaped poly-2-ethyl-2-oxazine is close to 53 °C.
Star-shaped four-arm poly-2-ethyl-2-oxazine with calix4arene core was synthesized. Molar masses of the polymer star and its arms were 7100 and 1300 g·mol−1, respectively. The self-organization of molecules in aqueous solutions was investigated using light scattering and turbidity within a wide concentration interval. At room temperature, in solutions of synthesized polymer, in addition to macromolecules, a small fraction of aggregates is observed, which result from the interactions of hydrophobic branching centers. Phase separation temperatures decrease with increase in concentration. Low critical solution temperature for the investigated star-shaped poly-2-ethyl-2-oxazine is lower than LCST for aqueous solutions of linear and star-shaped poly-2-ethyl-oxazoline and higher than that for star-shaped poly-2-isopropyl-2-oxazine with calix4arene core and similar molar mass.
Abstract
Shock Ignition is a two-step scheme to reach Inertial Confinement Fusion, where the precompressed fuel capsule is ignited by a strong shock driven by a laser pulse at an intensity in the ...order of
$$10^{16}$$
10
16
W/cm
$$^2$$
2
. In this report we describe the results of an experiment carried out at PALS laser facility designed to investigate the origin of hot electrons in laser-plasma interaction at intensities and plasma temperatures expected for Shock Ignition. A detailed time- and spectrally-resolved characterization of Stimulated Raman Scattering and Two Plasmon Decay instabilities, as well as of the generated hot electrons, suggest that Stimulated Raman Scattering is the dominant source of hot electrons via the damping of daughter plasma waves. The temperature dependence of laser plasma instabilities was also investigated, enabled by the use of different ablator materials, suggesting that Two Plasmon Decay is damped at earlier times for higher plasma temperatures, accompanied by an earlier ignition of SRS. The identification of the predominant hot electron source and the effect of plasma temperature on laser plasma interaction, here investigated, are extremely useful for developing the mitigation strategies for reducing the impact of hot electrons on the fuel ignition.
Heat transfer in a drained channel of RBMK-1000 as it heats up during a severe beyond design basis LOC accident with destruction of the core is considered. Radiative heat exchange of a FA with a ...channel tube, in conjunction with molecular heat exchange in FA and the graphite column enclosing the channel is calculated. This is accomplished by means of precision models of heat transfer, based on ray tracing with adjustable spatial resolution. The calculated temperature behavior is determined by the well-known effect of the heat capacity of a graphite column, in the present case under the conditions of a beyond design basis accident, due to which the core and FA slowly heat up. This has the result that the fuel-rod cladding can heat up while the channel almost completely drained and in the absence of a developed steam-zirconium reaction. The obtained results could be helpful in building simplified approaches to modeling heat transfer in a RBMK-1000 core during a severe accident.
The results of a simulation of ACE MCCI test L8 facility (ANL, Argonne, USA) on the interaction of melt with concrete are presented. The objectives of this work are the validation of previously ...developed models of the melt–concrete interaction and an analysis of inconsistencies in the yield of carbon oxides, which are explained by aspects of the thermochemistry of the interaction. The computational and experimental results were compared by way of the advancement of erosion boundary of the concrete, the yield of hydrogen and carbon oxides from the melt, and the integral yield of the fission-product imitators. The agreement is satisfactory. The spread of the results on varying the main parameters of the calculation was assessed.
•Neglecting by heat radiation in simulation of containment tests may cause discrepancies.•To show that, heat exchange in T114 air-helium test was analyzed in different ways.•Effect of thermal ...radiation on local temperature was numerically obtained in air with ∼1% steam content.•Model of gas-structure heat exchange in containment should include heat radiation.
One of the experiments of ERCOSAM–SAMARA (E–S) projects (TOSQAN T114) is examined from the viewpoint of the radiative heat transfer (RHT) contribution to the overall heat exchange. E–S projects and T114 test were focused on investigation of light gas stratification in severe accident containment atmosphere and stratification break-up after the activation of mitigation systems. The first from two phases of T114 test is considered during which helium is quasistatically injected into the upper part of the TOSQAN vessel having isothermal walls and initially filled by air. The developing free convection removes most of the heat acquired, but not all. Thus stable local deviations in calculated temperatures were obtained in simulations that were interpreted as the deficiencies of the physical heat-transfer model. The modeling of RHT was included in full CFD simulation that resulted in a better agreement in local temperatures. The results of comparative calculations performed without/with RHT modeling are described in the paper. The RHT model implemented in the used CFD code (ANSYS FLUENT) was tested on known analytical solutions. The RHT contribution in T114 test was also estimated analytically to demonstrate independently that it may be noticeable in this experiment. The same estimations may be valid for stagnant zones of severe accident containment. All that shows the need in further detailing of the role of RHT in gas-structure heat exchange: as for interpretation of some containment tests performed in pressure vessel as for containment modeling.
The energy calculation of the hydroacoustic communication channel is divided into a number of interrelated stages: the choice of the operating frequency of the communication line; selection of sonar ...antennas; determination of the acoustic power of the signal. Experimental studies of hydroacoustic systems require significant financial costs. Therefore, recently, in order to reduce these costs, simulation models of individual nodes or even of the entire hydroacoustic system as a whole are resorted to. This work is devoted to the simulation modeling of a hydroacoustic channel antenna. A schematic diagram of the SKOL-2000R hydroacoustic antenna model is given, and the operating parameters of this model are chosen so that the resonant frequency of the model coincides with the resonant frequency of the original 29.6 kHz.
A kinetic model is proposed for ion–molecular processes involving charged particles of a humid air plasma produced by a fast electron beam. The model includes more than 600 processes involving ...electrons and 41 positive and 14 negative ions, including hydrated ions H
3
O
+
(H
2
O)
n
and O
2
−
(H
2
O)
n
with
n
= 1, 2, …, 12. The energy costs of production of electron–ion pairs and electronic and vibrational (for water molecules, also rotational) excitation of molecules are calculated in nitrogen, oxygen, water vapor, air, and humid air. A method is proposed for calculating the energy costs in mixtures by the calculation data in pure gases. The evolution of the plasma composition is studied by the numerical solution of a system of 56 time-dependent balance equations for the number of charged particles of plasma by the fourth-order Runge–Kutta method. The steady-state composition of plasma is determined by solving nonlinear steady-state balance equations for the ionization rates of humid air from 10 to 10
16
cm
–3
/s and the fraction of water molecules from 10
–3
% to 1.5%. It is established that, for water vapor content (the ratio of the number density of water molecules to the total number density of air molecules) of 0.015–1.5% in air at atmospheric pressure and room temperature, the main ion species are two types of positive ions H
3
O
+
(H
2
O)
n
with the number of water molecules
n
= 5, 6 and three species of negative ions O
2
−
(H
2
O)
n
with
n
= 5, 8, 9.
Novel materials with a variety of properties, such as biocompatibility, antibacterial activity, interconnected porosity, and functionalities combined in one, are required for regenerative medicine. ...Porous β-tricalcium phosphate (β-TCP) ceramics doped with Cu
2+
, Zn
2+
, Ag
+
, and Fe
3+
ions in the concentrations of less than 0.5 wt.% were synthesized and investigated. The obtained samples were analyzed by the diversity of analytical tools. The structure, solubility, and antimicrobial properties of the porous ceramics are shown to be very sensitive to the presence and the type of the cationic substituent. It opens the way to manage structure and properties of the materials for bone tissue regeneration by co-doping of the initial matrix simultaneously with different types of substituent ions.
The paper considers refined approaches to solving two problems of modeling MCCI: (1) a thermodynamical model of chemical reactions of the concrete components with the melt was constructed, as well as ...a model of concrete decomposition including universal procedures for calculating the heat capacity and density of concrete, independently on its type; (2) a self-consistent, cost-effective model of concrete ablation progression was constructed, taking into account heating of the concrete; this model numerically solves the heat conduction equation on an adaptive grid. The models are described and verified.
The problem of optimal control of the relative motion of a spacecraft with a finite thrust engine in arbitrary circumcircular orbits using the Pontryagin’s maximum principle is considered. Motion is ...studied in an orbital cylindrical coordinate system, using variables written in the form of secular and periodic components of relative motion in the orbital plane. The main attention is paid to the analysis of the optimal control structure with a free and transversal orientation of the thrust vector in the presence of passive areas on the trajectory. As a criterion for choosing the optimal control, the motor operating time of the corrective motors was considered. Characteristic control structures for various areas of initial driving conditions have been determined, and estimates of the marginal costs of motor time have been obtained.
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