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Incubation time approach in rock fracture dynamics

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Science China(Physics,Mechanics & Ast.onomy) 2012年第1期55卷 78-85页

作者： SMIRNOV V PETROV Yuri V BRATOV V st.-petersburg state transport university 198103 St.-Petersburg Russia st.-petersburg state university 198504 St.-Petersburg Russia Inst.tute of Problems of Mechanical Engineering Russian Academy of Sciences 199178 St.-Petersburg Russia

The paper is summarizing latest.results connected with application of the incubation time approach to problems of dynamic fracture of rock materials. Incubation time based fracture criteria for intact media and media with cracks are discussed. Available experimental data on high rate fracture of different rock materials and incubation time based fracture criteria are used in order to evaluate critical parameters of causing fracture in these materials. Previously discovered possibility to optimize (minimize) energy input for fracture is discussed in connection to indust.ial rock fracture processes. It is shown that optimal value of momentum associated with critical load in order to initialize fracture in rock media does st.ongly depend on the incubation time and the impact duration. Exist.nce of optimal load shapes minimizing momentum for a single fracturing impact or a sequence of periodic fracturing impacts is demonst.ated.

关键词： incubation time dynamic fracture rocks dynamic st.ength fracture toughness crack resist.nce energy and momentum input fracture process optimization

Generalized quantum mechanical two-Coulomb-center problem (Demkov problem)

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Chinese Physics B 2013年第9期22卷 245-251页

作者： A.M.Puchkov A.V.Kozedub E.O.Bodnia Theoretical Department Institute of PhysicsSt. Petersburg State University Department of Computational Physics Faculty of PhysicsSt. Petersburg State University

We present a new exactly solvable quantum problem for which the Schrtidinger equation allows for separation of variables in oblate spheroidal coordinates. Namely, this is the quantum mechanical two-Coulomb-center problem for the case of an imaginary intercenter parameter and complex conjugate charges are considered. Since the potential is defined by the two-sheeted mapping whose singularities are concentrated on a circle rather than at separate points, there arise additional possibilities in the choice of boundary conditions. A detailed classification of the various types of boundary-value problems is given. The quasi-radial equation leads to a new type of boundary value problem which has never been considered before. Results of the numerical calculations, which allow conclusions to be drawn about the st.ucture of the energy spectrum, are shown. Possible physical applications are discussed.

关键词： two-Coulomb-center problem potential models

On the primitive divisors of the recurrent sequence un＋1=(4cos^2(2π/7)-1)un-un-1 with applications to group theory

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Science China Mathematics 2018年第11期61卷 2101-2110页

作者： Maxim Vsemirnov st. petersburg Department of V.A. st.klov Inst.tute of Mathematics St. Petersburg 191023 Russia Department of Mathematics and Mechanics St. Petersburg State University St. Petersburg 198504 Russia

Consider the sequence of algebraic integers un given by the st.rting values u0=0,u1=1 and the recurrence u_(n+1)=(4cos^2(2π/7)-1)u_n-u_(n-1).We prove that for any n ■{1,2,3,5,8,12,18,28,30}the n-th term of the sequence has a primitive divisor in Z[2 cos(2π/7)].As a consequence we deduce that for any sufficiently large n there exist. a prime power q such that the groupcan be generated by a pair x,y with χ~2=y^3=(xy)~7=1 and the order of the commutator[x,y]is exactly *** latter result answers in affirmative a quest.on of Holt and Plesken.

关键词： recurrent sequences primitive divisors Hurwitz groups

Transient near tip fields in crack dynamics

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Science China(Physics,Mechanics & Ast.onomy) 2011年第7期54卷 1309-1318页

作者： BRATOV Vladimir PETROV Yuri UTKIN Alexander Inst.tute of Problems of Mechanical Engineering Russian Academy of SciencesSt.-Petersburg 199178Russia st.-petersburg state university St.-Petersburg 198504Russia

Transient effects of st.ess-st.ain fields in the vicinity of a st.tionary crack tip under high rate loads are *** analytical solutions to near tip st.esses are compared to fields prescribed by leading terms(one or several) of Williams asymptotic *** of load application mode,time(or,which is the same,dist.nce from a crack tip) and Poisson's ratio on this discrepancy is extensively *** effects connected with crack tip propagation speed are also *** inconsist.ncies between real(or received in numerical solutions of state *** element computations) crack tip fields and st.ess intensity factor(SIF) singular field observed by numerous researchers are *** scope of problems where SIF field can be used for correct prediction of dynamic st.ess-st.ain fields in the crack tip region is *** to correctly approximate fields that are not SIF dominated,accounting additional terms of Williams expansion,is st.died.

关键词： transient crack tip fields dynamic fracture high-rate loads asymptotic expansions

Brief Review of N2O Decomposition Catalyst. for Engines

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火炸药学报 2020年第2期43卷 116-132页

作者： A.A.Boryaev Saint petersburg state university of Architecture and Civil Engineering 4 Vtoraya Krasnoarmeyskaya St.Saint Petersburg190005Russia

A brief review of nitrous oxide decomposition catalyst. was *** features of catalyst.operating conditions in low-thrust.engines of space vehicles and requirements to monopropellant(hydrogen peroxide,hydrazine,nitrous oxide)decomposition catalyst. were considered.A scientific basis for development of a nitrous oxide decomposition catalyst.and general principles for selection of efficient catalyst. were *** results of selecting catalyst.syst.ms for the development of decomposition catalyst. for N2O as a monopropellant were *** selection of catalyst.syst.ms for the development of a catalyst.designed for low-thrust.rocket engines(LTREs)was carried out:supporter—Al2O3 and ZrO2;active subst.nces—Co,Ni,Fe,Pd,Rh,Pt,Ru,Ir,NiO,Fe2O3,RuO2,Rh2O3,PdO,IrO2,PtO2,CoO,Al2O3,La2NiO4,Nd2NiO4,Pr 2NiO4,La2O3,TiO2,NiO,La2O3,TiO2,*** 71 references.

关键词： propellant nitrous oxide catalyst low-thrust rocket engine

Use of Hydrazine and Its Subst.tutes as Fuel

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火炸药学报 2022年第2期45卷 164-178,I0001页

作者： A.A.Boryaev Saint petersburg state university of Architecture and Civil Engineering 4 Vtoraja Krasnoarmejskaja St.Saint Petersburg 190005Russia

Due to the properties and high reactivity of hydrazine,it is mainly used as rocket fuel not only in its pure form but also in combination with 1,1-dimethylhydrazine and oxidizers(nitrogen tetroxide or nitric acid)forming a self-igniting mixture with *** 50 and UH 25(a mixture of 75%UDMH(unsymmetrical dimethylhydrazine)and 25%hydrazine hydrate)are the best.known hydrazine mixtures with different hydrazine *** review addresses the use of hydrazine and its derivatives as *** is employed in fuel cells(with air oxygen as an oxidizer)to generate electrochemical energy for transport *** is widely used as monopropellant to design low-thrust.rocket engines for orientation and st.bilization syst.ms in space vehicles,as well as in energy *** review also addresses such hydrazine derivatives as methylhydrazine,1,1-dimethylhydrazine,hydrazine monoperchlorate,hydrazine diperchlorate,hydrazine diammonium tetraperchlorate,hydrazine mononitrate,hydrazine dinitrate,hydrazine nitroformate,hydrazine azides,tetrafluorohydrazine,*** well as composite propellants,and gel rocket propellants based on *** materials in the review can be used as reference information on hydrazine fuels.

关键词： liquid fuel hydrazine fuels based on hydrazine derivatives properties and scope of application

Search for Effective Catalyst. for the Development of Engines Based on the Products of Catalytic Decomposition of N_(2)O

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火炸药学报 2021年第1期44卷 8-20,40页

作者： A.A.Boryaev Saint-petersburg state university of Architecture and Civil Engineering 4 Vtoraya Krasnoarmeyskaya St.Saint-Petersburg 190005Russia

The paper presents requirements for the N_(2)O decomposition catalyst.and provides just.fication for the selection of components to develop its *** methods to st.dy the physical and chemical as well as catalytic properties of catalyst. were developed,and the results of experimental st.dies on the properties of catalyst. with different composition in the laboratory conditions were *** activity of samples of compact metal catalyst. as well as samples of supported metal and oxide catalyst. in the nitrous oxide decomposition reaction was *** methodology for determining the activity of catalyst. in the decomposition reaction of N_(2)O is presented,as well as the design of an experimental reactor for determining the activity of the catalyst.by the minimum temperature for the onset of the decomposition reaction of N_(2)*** the course of the st.dy,the following series of catalyst.activity are determined in the N_(2)O decomposition reaction up to a temperature of 600℃:based on platinum group metals applied to the aluminum oxide carrier-Rh>Ru>Ir>Pt>Pd;based on simple oxides applied to the aluminum oxide carrier-CoO>Cr_(2)O_(3),MnO_(2)>CuO>ZrO_(2)>NiO>Fe_(2)O_(3).The following activity series for the most.promising carriers are also determined:by the onset temperature of decomposition,ZrO_(2)>Al_(2)O_(3)-CaO>Al_(2)O_(3)-ZrO_(2)>Al_(2)O_(3)-AlN>θ-Al_(2)O_(3)>Al_(2)O_(3)-SiO_(2)>SiO_(2)>α-Al_(2)O_(3);by the rate const.nts of N_(2)O decomposition,Al_(2)O_(3)-SiO_(2)>Al_(2)O_(3)-AlN>ZrO_(2)>Al_(2)O_(3)>Al_(2)O_(3)-ZrO_(2)>Al_(2)O_(3)-CaO>α-Al_(2)O_(3)>SiO_(2).The paper presents the results of selecting the active component and carriers for the supported *** author proposes formulations of the nitrous oxide decomposition catalyst.for bench test.ng in simulated engines.

关键词： nitrous oxide engines catalyst properties formulation

Resonance Conversion as the Effective Way of Triggering the ^（178m2）Hf Isomer Energy

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Chinese Physics Letters 2006年第8期23卷 2049-2051页

作者： F. Feodor KARPESHIN M. B.TRZHASKOVSKAYA 张景波 Science Center and Department of Physics Harbin Institute of Technology Harbin 150001 Fock Inst.tute of Physics St. Petersburg State University RU-198504 St. Petersburg Russia PNPI RU-198355 St. Petersburg Leningrad District Russia

Experiments on photo-induced de-excitation triggering of ^（178m2）Hf are revisited. We present an alternative and more effective way of triggering by exploiting the resonance internal conversion. Full theoretical description of a possible channel is presented. It is therefore revisited the impact itself produced by those experiments.

关键词： Resonance Conversion Effective Way

Resonance Conversion as a Catalyzer of Nuclear Reactions

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Chinese Physics Letters 2006年第9期23卷 2391-2394页

作者： KARPESHIN Feodor 张景波张卫宁 Science Center and Department of Physics Harbin Institute of Technology Harbin 150001 Fock Inst.tute of Physics St. Petersburg State University RU-198504 St. Petersburg Russia

It is shown that resonance internal conversion offers a feasible tool for mast.ring nuclear processes with laser or synchrotron radiation. The physics of the process is discussed in detail in a hist.rical aspect. Possible experimental application is shown in the case of the M1 70.6-keV transition in nuclei of 169 Yb. The nuclear transition rate in hydrogen-like ions of this nuclide can be enhanced by up to four orders of magnitude.

关键词： INTERNAL-CONVERSION TRANSITIONS EXCITATION FISSION ATOMS IONS E2