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На севере Сибирской платформы выделена Котуйканская кольцевая структура, которую по дистанционным, космогеологическим, тектоническим, геофизическим, структурно-вещественным и изотопно-геохронологическим критериям можно идентифицировать как крупную палеопротерозойскую астроблему Земли, сравнимую с такими близкими по возрасту импактными структурами, как Вредефорт и Садбери. Кроме того, здесь же выявлены косвенные признаки еще двух крупных структур подобного генезиса. Тем самым подтверждается предположение многих ученых о массированной бомбардировке поверхности ранней Земли крупными астероидами и о возможном влиянии масштабных импактных событий на динамику мантии Земли и ротационный режим планеты, т.е на ход ее тектонической эволюции, включая процессы тектоники плит.

В геологической истории неопротерозоя юго-восточной части Восточного Саяна реконструированы две разновозрастные островные дуги: Дунжугурская и Шишхидская. Ранее считалось, что Дунжугурская дуга возникла около 1020 млн лет назад и испытала коллизию с Сибирским (?) континентом около 810 млн лет. Шишхидская дуга возникла несколько ранее чем 800 млн лет и существовала до конца позднебайкальского этапа (около 600 млн лет по косвенным данным). Такая примитивная геологическая история, в которой каждая из дуг существовала на протяжении 200 млн лет, обусловлена неполнотой прямых данных и заставляла сомневаться в корректности предложенных реконструкций. В работе приведены результаты предварительного датирования детритовых цирконов, извлеченных из вулканокластических пород, связанных с упомянутыми дугами. Для Дунжугурской вулканокластики проанализировано 12 кристаллов, возраст которых лежит в интервале 844 ± 8—1048 ± 12 млн лет (²⁰⁶Pb/²³⁸U, 1σ). Пять наиболее древних цирконов образуют конкордантный кластер с возрастом 1034 ± 9 млн лет (2σ). Следовательно, дуга возникла ранее, чем предполагалось, и действительно существовала долго, по-видимому, до момента ее коллизии с континентом. Из вулканокластических пород, заключенных в Окинской аккреционной призме, предположительным источником которых является Шишхидская дуга, изучены два образца. Все 10 кристаллов первого образца образуют конкордантный кластер с возрастом 813 ± 7 млн лет (2σ). Проанализированные цирконы второго образца группируются в два кластера: 775 ± 8 млн лет (2σ, 9 кристаллов) и 819 ± 17 млн лет (3 кристалла). Таким образом, Шишхидская дуга возникла ранее, чем предполагалось, фактически в конце раннебайкальского этапа и характеризовалась активным вулканизмом, по крайней мере, до 775 млн лет. Прогнозируется, что полноценное датирование детритовых цирконов из вулканокластики зрелого этапа Шишхидской дуги позволит полностью или частично документировать интервал 775—600 млн лет.

The concept of turbulent burning velocity arises from an analogy with that of the laminar burning velocity. Experimental measurement or theoretical computation of .the latter must take account of the effects of flame stretch. This is also necessary for turbulent flames and when flame propagation originates at a point source, there is a temporal development of the turbulence acting on the flame and also of the thickness of the flame brush. Under these conditions, whilst the turbulent burning velocity is a measure of the propagation rate of the front relative to unburnt mixture, it cannot be a direct measure of the mass rate of burning.

Tliis paper reports the thermal decomposition pattern of GAP and GAP containing double base (DB) compositions. Dynamic and isothermal TGA reveal two stage decomposition process for GAP. At temperatures below 200° С reactant-product interface diffusion while at higher temperatures, nucleation based diffusion processes appear to be operative. Inclusion of GAP resulted in drop in temperature for onset of free radical reaction.

A theoretical and experimental investigation is being conducted on the effect of a dynamic external radiant heat flux on the combustion of energetic materials. These studies have illustrated the need for including the effect of the mean radiant heat flux and in-depth absorption. Also, a method for obtaining the linear frequency response function over a range of frequencies from a single test using series of radiant pulses is demonstrated. Experimental results have been obtained for an AP/HTPB propellant.

The experimental study of the frequency response of burning solid propellants has been done using, as external forcing energy source, a CO₂ laser (60 W, 10.6 pm). The laser radiant flux intensity was sinusoidally modulated and the response of the burning propellant was detected measuring the recoil force generated by the gases coming out from the burning surface using a strain-gage load cell which can operate inside the combustion chamber at the operating pressure. The tests were performed in the subatmospheric pressure range and a composite propellant (AP.HTPB/86.14) was used. The combustion chamber was filled by inert gas (N₂) and for each working pressure several tests were carried out at different radiant flux frequency modulations in the range from 5 to 50 Hz. The results evince that the recoil force amplitude depends on the forcing laser frequency with a maximum for every working pressure. This experimental data set was then used to compare the nonlinear frequency response curves obtained by numerical integration of the combustion model equations. Comparisons between experimental and numerical results at 0.3 and 0.5 atm are shown and the general trend, obtained by numerical simulations, of the propellant frequency response vs pressure in a broader range is presented and discussed.

The interaction between radiation and combustion is studied theoretically in the case of strained counterflow nonluininous laminar flames. Both H₂ – 0₂ diffusion and C₃H8 – air premixed flames are considered. Calculations are based on detailed chemical kinetics and narrow-band statistical modeling of infrared radiative properties. It is shown that radiative transfer decreases the temperature level, which affects particularly the production and consumption of minor species and pollutants. For H₂ – 0₂ flames, a low strain rate extinction limit due to radiation is found. It is also shown that the commonly used approximation of optically thin medium is inaccurate, even for the small scale laboratory flames considered here.

In the present article, we analyze the nonsteady behaviour of counterflow diffusion flames submitted to a time dependent injection velocity in the case of hydrogen — air flames. The numerical study, using a finite difference implicit Linear Multistep Method and employing complex kinetics, is done for sinusoidal injection velocity variations, for moderate values and also for values near the extinction limit. The frequency response is obtained in these different cases. The experimental setup comprises two axisymmetric nozzles. In order to change the inlet velocities periodically, we use a vibrating mechanism in each burner. The amplitude and the frequency of injection velocities of the opposed nozzles are synchronously modified. The OH radical emission intensity is used to measure the flame response to velocity fluctuations. The experimental results are compared to numerical calculations. A good concordance is obtained in this comparison.

The nonequilibrium gasdynamics processes of importance to hypersonic aerobraking vehicles are reviewed. Recent improvements in understanding these phenomena and in the detailed numerical modeling of these processes will be discussed. The paper concludes by describing the extent to which these models have been incorporated into multidimensional computational fluid dynamics (CFD) computer codes.

Aluminum is widely used in modern solid rocket propellants for many purposes, but mainly to increase the specific impulse by raising the flame temperature. Most of the aluminum, present in powder state in the propellant, do not vaporize onto the burning surface so tending later to agglomerate into large particles difficult to burn even in the flame. The aim of this work is to study the behavior of the aluminum particles onto the burning surface and into the gaseous region of the propellant flame structure. Different diagnostic techniques have been used: SEM on the burning surface of extinguished samples, pictures taken during combustion by filtered still camera and a new developed laser diagnostic. By the use of an UV laser beam and a high speed shutter TV camera, the Al particles onto the burning surface has been visualized. A suitable Image Processor to extract information from the frames has been adopted. Tests on a HTPB.12/AP.68/A1.20 propellant in the pressure range 10–50 atm has been performed. Results show the reliability of the diagnostics here used and have contributed to a better characterization of the tested propellant.