Dependability modeling framework : a test procedure for high availability in cloud operating systems

This paper describes a framework on how to test High Availability capabilities of cloud architectures, particularly OpenStack. The “Dependability Modeling Framework” which consists of a modelling of the system parts, user interactions and dependencies between them will form the basis for this test. The test procedure consists of simulating random shutdown of system components, polling the availability of user interactions and measuring the impact of outages and expected downtime. Outage impacts and downtime are used to rate the underlying system architecture. The test procedure is applied on a single node OpenStack installation in order to show validity of the test concept

Elastic scaling of cloud application performance based on Western Electric rules by injection of aspect-oriented code

The main benefit of cloud computing lies in the elasticity of virtual resources that are provided to end users. Cloud users do not have to pay fixed hardware costs and are charged for consumption of computing resources only. While this might be an improvement for software developers who use the cloud, application users and consumers might rather be interested in paying for application performance than resource consumption. However there is little effort on providing elasticity based on performance goals instead of resource consumption. In this paper an autoscaling method is presented which aims at providing increased application performance as it is demanded by consumers. Elastic scaling is based on “statistical process monitoring and control” and “Western Electric rules”. By demonstrating the architecture of the autoscaling method and providing performance measurements gathered in an OpenStack cloud environment, we show how the injection of aspect-oriented code into cloud applications allows for improving application performance by automatically adapting the underlying virtual environment to pre-defined performance goals. The effectiveness of the autoscaling method is verified by an experiment with a test program which shows that the program executes in only half of the time which is required if no autoscaling capabilities are provided

1-Nitrimino-5-azidotetrazole: Extending Energetic Tetrazole Chemistry

Azide and nitrimino functions are among the most energetic substituents that can be introduced to the skeleton to enhance the energetic properties of a compound. In this study, we report the successful synthesis of a compound that combines both, azide and nitrimino substituents directly attached to one tetrazole scaffold. 1-Nitrimino-5-azidotetrazole is prepared by nitration of 1-amino-5-azidotetrazole. Subsequent salination with ammonia and guanidinium carbonate yields two highly energetic derivatives. All energetic compounds, as well as the intermediate steps of an alternatively developed synthesis strategy, were analysed and characterized in detail. In addition to multinuclear NMR and IR spectroscopy, crystal structures of all key compounds were measured. The sensitivities (friction, impact, electrostatic discharge and thermal) were determined accordingly. In addition, the detonation parameters of all energetic substances were calculated with the EXPLO5 code, which was fed with the enthalpy of formation (atomization method based on CBS-4M) and the crystallographic densities

Linear Correlation Between Confined Explosive Quantity and Dent Volume of an Underlying Aluminium Block Using the SSRT Setup

The SSRT setup gives smart access to test various properties of explosive materials and requires only little substance quantities. Unlike the standardized SSRT, we studied the bulge development from the blast of different amounts of PETN (200-1300 mg). The bulge of the corresponding aluminum blocks was evaluated with the help of a profilometer (Keyence VR-5200). This device, which measures the volume of the dents using the offset of structured light projected on the object, has allowed us to analyze the differences precisely. Despite the experimental limitations and the resulting undirected explosion direction, a throughout linear correlation between the respective amounts of PETN and the resulting dent depth could be determined. Our study thus forms an illustrative development of how the explosion behavior, represented by the dent of an aluminum block, of compressed energetic materials behaves in with increasing filling quantity, which is transferable to larger experimental setups as well as to other explosives

Monitoring resilience in a rook-managed containerized cloud storage system

Distributed cloud storage solutions are currently gaining high momentum in industry and academia. The enterprise data volume growth and the recent tendency to move as much as possible data to the cloud is strongly stimulating the storage market growth. In this context, and as a main requirement for cloud native applications, it is of utmost importance to guarantee resilience of the deployed applications and the infrastructure. Indeed, with failures frequently occurring, a storage system should quickly recover to guarantee service availability. In this paper, we focus on containerized cloud storage, proposing a resilience monitoring solution for the recently developed Rook storage operator. While, Rook brings storage systems into a cloud-native container platform, in this paper we design an additional module to monitor and evaluate the resilience of the Rook-based system. Our proposed module is validated in a production environment, with software components generating a constant load and a controlled removal of system elements to evaluate the self-healing capability of the storage system. Failure recovery time revealed to be 41 and 142 seconds on average for a 32GB and a 215GB object storage device respectively

Evaluation of SSRT-Test by Classical Gravimetric Analysis and Optical Topographic Measurement: A Comparative Study

To establish a database of performance values in the small-scale shock reactivity test (SSRT), common secondary explosives based on organic nitrates (e. g. PETN) and nitramines (e. g. RDX and HMX) as well as aromatic (e. g. TNT), heteroaromatic (e. g. TKX-50 and MAD-X1) and open chain systems (e. g. FOX-7) were investigated. The evaluation of the test results was carried out by two different methods. On the one hand, manually by weighing out the resulting dents with sand, and on the other hand, optically with the aid of a profilometer. The two analysis methods were compared and evaluated with respect to their absolute results and absolute as well as relative standard deviations

Tuning the Properties of 5-Azido and 5-Nitramino-tetrazoles by Diverse Functionalization - General Concepts for Future Energetic Materials

5-Azido and 5-nitraminotetrazole backbones are established heterocyclic motifs in the research field of energetic materials synthesis. Despite the high energy content of the compounds, the problem with many derivatives is that their sensitivities are far too high. Functionalization of one of the ring nitrogen atoms is the aim of this study to adjust the sensitivity by inserting nitratoethyl, azidoethyl and methyl groups. In this context, derivatives of 2-(2-azidoethyl)-5-nitraminotetrazoles (2, 2a-2d), as well as 1-nitrato and 1-azidoethyl substituted 5-azidotetrazole (7 and 10) and the methylation products of 5-azidotetrazole (5-azido-1-methyl-tetrazole, 11 and 5-azido-2-methyl-tetrazole, 12) were prepared. The obtained nitrogen-rich compounds were extensively characterized through multinuclear NMR spectroscopy and IR spectroscopy. The structural confinement was checked by X-ray diffraction experiments. The pure samples (verified by elemental analysis) were investigated regarding their behavior toward friction, impact (BAM methods) and electrostatic discharge as well as heating (DTA and DSC). For all metal-free compounds the detonation properties were computed with the EXPLO5 code using their density and heat of formation, calculated based on CBS-4 M level of theory