Effect of Thermal Resistance of the Dielectric–Metal Contact on the Temperature Field in a Dielectric Exposed to Ion Beams

Heating of MgO crystals exposed to repetitively pulsed ion beams is studied. A solution to the thermal-conductivity equation provides induced specimen-temperature variations about a mean with irradiation-pulse repetition rate. The average temperature during the variation period first increases and then saturates, approaching a quasi-stationary value <T>. The latter depends entirely on the thermal resistance of the specimen–substrate contact under fixed irradiation conditions. A rapid method for determining the thermal resistance of the contact is put forward. The approach is based on repetitive pulsed heating of the specimen by a moderate-density electron beam and on precision measurements of average temperature.     

Conformal Hamiltonian dynamics of general relativity

The General Relativity formulated with the aid of the spin connection coefficients is considered in the finite space geometry of similarity with the Dirac scalar dilaton. We show that the redshift evolution of the General Relativity describes the vacuum creation of the matter in the empty Universe at the electroweak epoch and the dilaton vacuum energy plays a role of the dark energy.     

Effect of molding conditions on fracture mechanisms and stiffness of a composite of grid structure

Methods of determining a complex of stiffness and deformability characteristics of a composite with rhomb-type grid structure were elaborated. Rhomb-type specimens were used for testing the ribs of the structure in tension, compression, and bending and the nodal points in shear in the plane of the ribs. The effect of additional tensioning of the ribs preceding the curing of the binder was investigated (ten tensioning levels ranging from 8 to 70 N/bundle with a linear density of 390 tex were applied). In testing epoxy-carbon specimens (UKN-5000+EHD-MK) in compression and tension, the failure mode changed depending on the tensioning level, i.e., the presence or absence of delamination and the appearance of dry fibers were detected. Dependences of the mechanical properties on tensioning were of a markedly pronounced extreme nature. The methods elaborated allow us to investigate the effect of other molding parameters, as well as the conditions and nature of loading, on the mechanical characteristics of composites.Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 1, pp. 71–78, January–February, 1999.     

Bound states in the continuum in open Aharonov-Bohm rings

Using the formalism of the effective Hamiltonian, we consider bound states in a continuum (BIC). They are nonhermitian effective Hamiltonian eigenstates that have real eigenvalues. It is shown that BICs are orthogonal to open channels of the leads, i.e., disconnected from the continuum. As a result, BICs can be superposed to a transport solution with an arbitrary coefficient and exist in a propagation band. The one-dimensional Aharonov-Bohm rings that are opened by attaching single-channel leads to them allow exact consideration of BICs. BICs occur at discrete values of the energy and magnetic flux; however, it’s realization strongly depends on the way to the BIC point. The text was submitted by the authors in English.     

Regioselective synthesis of 4-aryl-3,4-dihydro-1,3,5-triazino[2,1-<Emphasis Type="Italic">a</Emphasis>]isoindol-2-ones

The condensation of binucleophilic 3-amino-1-arylimino-1H-isoindoles with bifunctional 1-chloro-benzylisocyanates occurs regioselectively resulting in 3,4-dihydro-1,3,5-triazino[2,1-a]isoindol-2-one derivatives. The structures of the synthesized compounds were unambiguously established by NOE experiments. Correspondence: Olha V. Hordiyenko, Chemistry Department, Kyiv National Taras Shevchenko University, 01033 Kyiv, Ukraine.     

Study of coatings based on titanium oxides and oxynitrides using a set of methods

A set of methods has been applied to study the properties of titanium oxide and oxynitride coatings on steel. It is established that the coatings consist of two phases with a nanocrystalline and an amorphous structure with a high proportion (～50 %) of grain boundaries; anatase is the dominant crystalline phase. The obtained results can be applied in the development of coatings for stents as well as for manufacturing hydrogen accumulators.