Distributed OAIS-Based digital preservation system with HDFS technology

The paper describes architecture of a distributed OAIS-based digital preservation system which uses HDFS as a file storage system and supports wide distribution on a number of cluster's nodes. It is based on Apache Hadoop framework - a reliable open source solution with well horizontally scalable distributed architecture. Novelty of the proposed system is defined by the fact that none of existing OAIS digital preservation systems use HDFS storage for both structured and unstructured data archiving. Implementation of the system's prototype and results of its testing are also shown

Study of the nitrocellulose gunpowder regeneration process using hydrogen peroxide

World experience in storing ammunition shows that during long-term storage, pyroxylin gunpowders used in ammunition are capable of arbitrarily undergoing various physical and chemical transformations, which negatively affects the ballistic characteristics of ammunition. In some countries, ammunition is in use with a shelf life of 30–35 years or more. Factors influencing the physicochemical stability of gunpowder charges during long-term storage have been identified. An analysis of the chemical processes occurring in nitrocellulose gunpowders (NCP) during long-term storage is carried out, and the possibility of regenerating NCP by treatment with hydrogen peroxide is substantiated. It is indicated that there are no methods for regenerating gunpowder charges with long shelf life. It has been shown that one of the ways to increase the ballistic and energy characteristics of long-term storage ammunition can be the regeneration of nitrocellulose gunpowder charges. Data are presented on an experimental study to determine the characteristics of NCP after regeneration. It has been shown that when regenerating nitrocellulose gunpowder charges with hydrogen peroxide, the calorific value of the starting material increases. Based on the results obtained, an approach to assessing the feasibility of using regeneration technology is proposed. This approach is based on the effect of mass replenishment during the regeneration process due to ongoing chemical processes and heat and mass transfer. The ways for further research on the use of nitrocellulose as a high-calorie fuel are presente

Big Data Processing System for Analysis of GitHub Events

International audienc

Conversion of abstract behavioral scenarios into scenarios applicable for testing

International audienceIn this article, an approach of detailing verified test scenarios for developed software system without losing the model's semantics is proposed. Existing problem of generating test cases for real software systems is solved by using multi-level paradigm to obtain the real system signals, transactions and states. Because of this, the process is divided into several steps. Initial abstract traces (test cases) with symbolic values are generated from the verified behavioral model of software product. On the next step, called concretization, these values in test scenarios are replaced with concrete ones. Resulting concrete traces are then used as input for the next step, data structures conversion. This step is needed because concrete traces do not contain all the information for communicating with developed software and presented in another way with different data structures. After concrete test scenarios are detailed, they can be used for generation of executable test cases for informational and control systems. In this paper, a software tool is suggested for detailing test scenarios. It consists of several modules: a Lowering editor that allows user to create rules of detailing a signal, a Signals editor used to define complex data structures inside the signal and a Templates editor that eases work with similar signals. Process of translating abstract data structures into detailed data structures used in system implementation is presented with examples

Design, Plant Test and CFD Calculation of a Turbocharger for a Low-Speed Engine

Various approaches and techniques are used to design centrifugal compressors. These are engineering one-dimensional and quasi-three-dimensional programs, as well as CFD Computational Fluid Dynamics (CFD) programs. The final judgment about the effectiveness of the design is given by testing the compressor or its model. A centrifugal compressor for an internal combustion engine turbocharger was designed jointly by the Research Laboratory “Gas Dynamics of Turbomachines” of Peter the Great St. Petersburg Polytechnic University (SPbPU) and RPA (Research and Production Association) “Turbotekhnika”. To check its dimensionless characteristics, the compressor was tested with two geometrically similar impellers with a diameter of 175 (TKR 175E) and 140 mm (TKR 140E). The mathematical model of the Universal Modeling Method calculates the efficiency in the design mode for all tests of both compressors with an error of 0.89%, and the efficiency for the entire characteristic with an error of 1.55%. The characteristics of the TKR 140E compressor were calculated using the ANSYS commercial CFD software. For TKR-140E, a significant discrepancy in the value of the efficiency was obtained, but a good agreement in the area of operation, which was not achieved in previous calculations. According to the calculation, the work coefficient is overestimated by 9%, which corresponds to the results of previous calculations by the authors

Issues of gas dynamic characteristics modeling: a study on a centrifugal compressor model stage

The paper presents the results of CFD-calculations of a centrifugal compressor stage with a high-pressure 3D impeller and a vaneless diffuser. The stage was designed by Prof. A. M. Simonov in the Problem Laboratory of Compressor LPI according to the following design parameters: flow rate coefficient 0.080, loading factor 0.74, and the relative Mach number 0.78. Two design grids were used: 2.4 and 4.4 million cells for the sector with one blade. The entire stage was calculated with a sparser grid. Special “Stage” interface conditions are used to interface the gas-dynamic parameters at the boundary regions. The SST turbulence model was used in the calculations. The results of efficiency characteristics and work coefficient comparison showed the following: in design flow rate all three variants of the calculation overstate the loading factor by 14.3%; the calculated characteristics of polytrophic work coefficient in the staging of 360 degrees are closest to the experimental characteristics, but the absolute value is greater than 12% at a flow rate coefficient of 0.085; the maximum calculated efficiency of a stage (the circle of 360 degrees) is almost equal to the measured maximum efficiency

IKMTSL-PTE, a Phospholipid-Based EPR Probe for Surface Electrostatic Potential of Biological Interfaces at Neutral pH: Effects of Temperature and Effective Dielectric Constant of the Solvent

The synthesis and characterization of a lipidlike electrostatic spin probe, (<i>S</i>)-2,3-bis­(palmitoyloxy)­propyl 2-((4-(4-(dimethylamino)-2-ethyl-1-oxyl-5,5-dimethyl-2,5-dihydro-1<i>H</i>-imidazol-2-yl)­benzyl)­disulfanyl)­ethyl phosphate (IKMTSL-PTE), are being reported. The intrinsic p<i>K</i>_a⁰ of IKMTSL-PTE was determined by X-band (9.5 GHz) electron paramagnetic resonance (EPR) titration of a water-soluble model compound, 4-(dimethylamino)-2-ethyl-2-(4-(((2-hydroxyethyl)­disulfanyl)­methyl)­phenyl)-5,5-dimethyl-2,5-dihydro-1<i>H</i>-imidazol-1-oxyl (IKMTSL-ME), an adduct of methanethiosulfonate spin label IKMTSL and 2-mercaptoethanol. The p<i>K</i>_a⁰ of IKMTSL-ME in bulk aqueous solutions was found to be significantly higher than that of 4-(((2-hydroxyethyl)­disulfanyl)­methyl)-2,2,3,5,5-pentamethylimidazolidin-1-oxyl (IMTSL-ME), an adduct of the corresponding methanethiosulfonate spin label IMTSL and 2-mercaptoethanol (17 °C, p<i>K</i>_a⁰ = 6.16 ± 0.03 vs 20 °C, p<i>K</i>_a⁰ = 3.33 ± 0.03, respectively). A series of EPR titration experiments with IKMTSL-ME in aqueous solutions containing 0–60% v/v isopropanol have been carried out at 17 and 48 °C to determine the effects of temperature and bulk dielectric permittivity constant, ε, on the probe p<i>K</i>_a. A linear relationship between the probe p<i>K</i>_a and ε has been established and found to be essentially the same at 17 and 48 °C. The polarity term contributing to the p<i>K</i>_a of IKMTSL-PTE at an uncharged lipidlike interface was determined by incorporating the probe into electrically neutral micelles formed from nonionic detergent Triton X-100, and it was found, similar to IMTSL-PTE, to be negative. In negatively charged DMPG lipid bilayers, IKMTSL-PTE exhibits ionization transitions with significantly higher p<i>K</i>_a values than those previously reported for IMTSL-PTE (e.g., at 17 °C, p<i>K</i>_aⁱ = 7.80 ± 0.03 vs p<i>K</i>_a⁰ = 5.70 ± 0.05). The surface electrostatic potentials of DMPG lipid bilayers calculated using IKMTSL-PTE titration data were found to be somewhat lower than those calculated using IMTSL-PTE. The lower values measured by IKMTSL-PTE are the likely consequences of the structure of the linker that positions the reporter nitroxide further away from the bilayer plane into aqueous phase. Overall, the ionization transitions of IKMTSL-PTE with p<i>K</i>_a values close to the neutral pH range make this lipidlike molecule a valuable spectroscopic EPR probe for studying the electrostatic phenomena at biological interfaces, including lipid bilayer/membrane protein systems, that could be unstable in the acidic pH range accessible by the previously available probes