A new reduced network to simulate detonations in superbursts from mixed H/He accretors

We construct a new reduced nuclear reaction network able to reproduce the energy production due to the photo-disintegration of heavy elements such as Ru, which are believed to occur during superbursts in mixed H/He accreting systems. We use this network to simulate a detonation propagation, inside a mixture of C/Ru. As our reference, we use a full nuclear reaction network, including 14758 reactions on 1381 nuclides. Until the reduced and full networks converge to a good level of accuracy in the energy production rate, we iterate between the hydrodynamical simulation, with a given reduced network, and the readjustment of a new reduced network, on the basis of previously derived hydrodynamical profiles. We obtain the thermodynamic state of the material after the passage of the detonation, and the final products of the combustion. Interestingly, we find that all reaction lengths can be resolved in the same simulation. This will enable C/Ru detonations to be more easily studied in future multi-dimensional simulations, than pure carbon ones. We underline the dependence of the combustion products on the initial mass fraction of Ru. In some cases, a large fraction of heavy nuclei, such as Mo, remains after the passage of the detonation front. In other cases, the ashes are principally composed of iron group elements.Comment: 6 pages, 12 figure

Effect of Initial Disturbance on The Detonation Front Structure of a Narrow Duct

The effect of an initial disturbance on the detonation front structure in a narrow duct is studied by three-dimensional numerical simulation. The numerical method used includes a high resolution fifth-order weighted essentially non-oscillatory scheme for spatial discretization, coupled with a third order total variation diminishing Runge-Kutta time stepping method. Two types of disturbances are used for the initial perturbation. One is a random disturbance which is imposed on the whole area of the detonation front, and the other is a symmetrical disturbance imposed within a band along the diagonal direction on the front. The results show that the two types of disturbances lead to different processes. For the random disturbance, the detonation front evolves into a stable spinning detonation. For the symmetrical diagonal disturbance, the detonation front displays a diagonal pattern at an early stage, but this pattern is unstable. It breaks down after a short while and it finally evolves into a spinning detonation. The spinning detonation structure ultimately formed due to the two types of disturbances is the same. This means that spinning detonation is the most stable mode for the simulated narrow duct. Therefore, in a narrow duct, triggering a spinning detonation can be an effective way to produce a stable detonation as well as to speed up the deflagration to detonation transition process.Comment: 30 pages and 11 figure

Odonats Of Beypazarı (Ankara)

Ülkemiz farklı sulak alanların çok olduğu bir coğrafyadadır. Odonatlar bulundukları habitatların çevre sağlığının göstergesi olması yanında, besin zincirinde de önemli bir yere sahiptir ve ekolojik dengenin korunmasında önemli rol oynarlar. Bundan dolayı odonatlar biyoçeşitlilik çalışmalarında da önemli böcek gruplarındandır. Sulak alan çeşitliliğinin yüksek olduğu Beypazarı ilçesinde yapılmış olan araştırmalar bölgenin tamamını temsil etmemektedir. Bundan dolayı Beypazarı odonatlarının biyolojik çeşitliliğinin daha detaylı olarak ortaya çıkarılması amaçlanmıştır. Bu çalışma ile Ankara ili Beypazarı ilçesinde, 2014 yılı mayıs-eylül ayları arasında yapılan arazi çalışmaları sonucunda 192 erkek ve 91 dişi olmak üzere 283 ergin birey atrap yardımıyla toplanmıştır. Örneklerin sistematik olarak değerlendirmesi yapıldığında 9 familya ve 18 cinse ait 24 tür ve 3 alttür belirlenmiştir. Araştırma alanında tespit edilen tür ve alttürlerin morfolojik özellikleri, habitatları, fenolojileri ve araştırma alanında yayılış bilgileri verilmiştir. Faunistin değerlendirmeler sonucunda ise tespit edilen türlerden Erythromma lindenii ve alttürlerden Aeschna isosceles antehumeralis Ankara ili faunası için ilk kez kaydedilmiştir. Ayrıca tespit edilen taksonların teşhis anahtarları, Dünya ve Türkiye yayılışları ile erkek ve dişi fotoğrafları da verilmiştir.Our country is a geographical region where a lot of different wetlands. Odonats; besides being indicators of environmental health of the habitat, because of have an important part in the food chain, they play a critical role in preserving the ecological balance. Therefore Odonats are one of the major insect groups in biodiversity studies. The researchs in the Beypazarı where the diversity of the wetlands is high, do not represent the complete section. Therefore it is intended to reveal the biological diversity of Odonats of Beypazari in more details. In this study, including 192 male and 91 female totally 461 adult Odonata samples which are collected around Beypazarı province of Ankara in May- September 2014 were collected by using sweep net. At the end of the systematic evaluations, 24 species and 3 subspecies belonging to 18 genus of 9 family were identified. Morphological characteristics, habitat, phenology and distribution in the study area of the identified species and subspecies were given. Also, as a result of the faunistic evaluations of the identified species Erythromma lindenii and subspecies Aeschna isosceles antehumeralis was recorded for the first time in Ankara's fauna. Besides, identification keys, distribution in Turkey and world, male and female photos belonging to the identified species were supplied