On the security of a chaotic encryption scheme: problems with computerized chaos in finite computing precision

Zhou et al. have proposed a chaotic encryption scheme, which is based on a kind of computerized piecewise linear chaotic map (PWLCM) realized in finite computing precision. In this paper, we point out that Zhou's encryption scheme is not secure enough from strict cryptographic viewpoint. The reason lies in the dynamical degradation of the computerized piecewise linear chaotic map employed by Zhou et al. The dynamical degradation of the computerized chaos induces many weak keys to cause large information leaking of the plaintext. In addition, we also discuss three simple countermeasures to enhance the security of Zhou's cryptosystem, but none of them can essentially enhance the security.     

在VxWorks嵌入式系统下实现自有协议开发

本文主要讲解如何通过VxWorks的MUX(多元网络接口)实现自有协议的开发.     

高速铁路Vx牵引变压器供电方式优化研究

针对我国高速铁路运行现状,提出一种新的牵引供电优化方案。通过对某客运专线的实测负荷数据分析,计算出其Vx牵引变压器在所提方案下的温升与寿命损失,从而提出可通过改进现有的供电方式,以实现高速铁路经济优化运行。     

Corrosion of UO2 and ThO2: A quantum-mechanical investigation

The addition of Th to U-based fuels increases resistance to corrosion due to differences in redox-chemistry and electronic properties between UO₂ and ThO₂. Quantum-mechanical techniques were used to calculate surface energy trends for ThO₂, resulting in (1 1 1) < (1 1 0) < (1 0 0). Adsorption energy trends were calculated for water and oxygen on the stable (1 1 1) surface of UO₂ and ThO₂, and the effect of model set-up on these trends was evaluated. Molecular water is more stable than dissociated water on both binary oxides. Oxidation rates for atomic oxygen interacting with defect-free UO₂(1 1 1) were calculated to be extremely slow if no water is present, but nearly instantaneous if water is present. The semi-conducting nature of UO₂ is found to enhance the adsorption of oxygen in the presence of water through changes in near-surface electronic structure; the same effect is not observed on the insulating surface of ThO₂.     

Protective Si-Al-O-Y glass coatings on stainless steel in situ prepared by combustion flame spraying

Surface treatments are a common solution for reducing wear and friction, as well as for increasing oxidation and corrosion resistances. Two refractory glass compositions in the SiO₂-Al₂O₃-Y₂O₃ system have been in situ deposited on AISI 304 stainless steel substrates by combustion flame spraying, with an oxyacetylene torch. Both compositions, 66SiO₂-22Al₂O₃-12Y₂O₃ mol.% (G) and 50SiO₂-30Al₂O₃-20Y₂O₃ mol.% (D), were formulated in the glass forming area; however, G is situated in the pure glass zone and D in a zone of glass formation where partial crystallizations occur. As-sprayed coatings had a thickness of 150-240 μm and were of glassy nature, although in D composition formation of Y₃Al₅O₁₂ and Y₂Si₂O₇ phases was observed. The influence of the Si/Al/Y ratios on the microstructure and properties of the coatings has been studied by scanning electron microscopy/energy-dispersive spectrometry (SEM-EDS), X-ray diffraction (XRD) and microhardness indentation tests. Properties of these coatings were compared to the bulk properties of the same composition glasses finding direct relationships between them.     

电焊机线圈温升检测技术探讨

本文介绍一种新的电焊机线圈温升检测技术的基本原理。利用这种方法,可以把被测量电阻值Rx转变为电压量Vx,并把它引入到计算机检测技术中。同时介绍了特别研制的“HRC-1电焊机热态电阻自动测试仪”的基本原理和技术指标,着重介绍了其中的技术关键精密恒流源和模入放大器及A/D转换两部分。     

A fast-valve system for characterizing effusive-flow properties of vapor-transport systems: RIB applications

Decay losses, associated with the times required for particles to diffuse from ISOL production targets and to effusively-flow to an ion source, must be reduced to as low as practically achievable levels in order to deliver useful beam intensities of short-lived isotopes for research at ISOL based Radioactive Ion Beam (RIB) facilities. We have developed a fast-valve system and complementary 3-D Monte-Carlo code which can be used separately or in combination to assess the effusive-flow properties of vapor-transport systems, independent of size, geometry and chemical properties of the transport species. In this report, we describe the fast valve and present time spectra and characteristic time data for noble gases flowing through serial- and parallel-coupled vapor-transport systems similar in geometry but longer than those used for RIB generation at the HRIBF with and without target coating matrices.     

Preparation, sintering and leaching of optimized uranium thorium dioxides

Mixed actinide dioxides are currently studied as potential fuels for several concepts associated to the fourth generation of nuclear reactors. These solids are generally obtained through dry chemistry processes from powder mixtures but could present some heterogeneity in the distribution of the cations in the solid. In this context, wet chemistry methods were set up for the preparation of U_1−xTh_xO₂ solid solutions as model compounds for advanced dioxide fuels. Two chemical routes of preparation, involving the precipitation of crystallized precursor, were investigated: on the one hand, a mixture of acidic solutions containing cations and oxalic acid was introduced in an open vessel, leading to a poorly-crystallized precipitate. On the other hand, the starting mixture was placed in an acid digestion bomb then set in an oven in order to reach hydrothermal conditions. By this way, small single-crystals were obtained then characterized by several techniques including XRD and SEM. The great differences in terms of morphology and crystallization state of the samples were correlated to an important variation of the specific surface area of the oxides prepared after heating, then the microstructure of the sintered pellets prepared at high temperature. Preliminary leaching tests were finally undertaken in dynamic conditions (i.e. with high renewal of the leachate) in order to evaluate the influence of the sample morphology on the chemical durability of the final cohesive materials.     

Analytical investigations of irradiated inert matrix fuel

Yttria stabilised zirconia (YSZ) inert matrix fuel (IMF) fabricated at PSI and irradiated 3 years in the Halden Material Test Reactor (HBWR) since 2000, has been examined by Electron Probe Microanalysis (EPMA) and Secondary Ion Mass Spectroscopy (SIMS) after irradiation and compared with data gained for the unirradiated material. The examined pellet cross-section was estimated to have an equivalent burn-up of 22 MW d kg⁻¹. EPMA measurements demonstrate that the burn-up was rather flat over more than the half pellet radius. A Pu consumption of about 2.5 wt% has been measured with a higher rate in the fuel border zone. The high fuel temperature is responsible for a certain homogenisation of the mineral phases in the fuel centre region whereas the border zone has remained rather with an as-fabricated phase distribution. The central part was also characterised by a dense porosity distribution as well as a temperature and relocation driven depletion of the volatile fission products Xe and Cs. In addition, SIMS has been realised on the same specimen in order to determine the semi-quantitative distribution of different isotopes in the pellet.     

Behaviour of helium after implantation in molybdenum

This study deals with the behaviour of helium in a molybdenum liner dedicated to the retention of fission products. More precisely this work contributes to evaluate the release of implanted helium when the gas has precipitated into nanometric bubbles close to the free surface. A simple model dedicated to calculate the helium release in such a condition is presented. The specificity of this model lays on the assumption that the gas is in equilibrium with a simple distribution of growing bubbles. This effort is encouraging since the calculated helium release fits an experimental dataset with a set of parameters in good agreement with the literature.