Suppressing Hydrogen Evolution by Aqueous Silicon Powder Dispersions by Controlled Silicon Surface Oxidation

Aqueous silicon dispersions are used to produce pyrotechnic time delay compositions. The propensity of silicon to react with water and to produce hazardous hydrogen gas must be suppressed. To this end, the effect of air heat treatment temperature on the rate of corrosion of silicon was investigated. It was found that four hour heat treatments at temperatures below 350 °C provided significant passivation. This is attributed to the removal of the hydroxyl groups present on the SiO₂ surface scale layer. It was found that thickening the silica layer, by heat treatment at higher temperatures, causes a further reduction in the amount of hydrogen released. However, differential thermal analysis (DTA) studies showed that excessive silicon surface oxidation increased the ignition temperature and reduced the heat release of a near‐stoichiometric silicon‐lead chromate pyrotechnic composition.     

Deliberate ignorance in project risk management

The management of project risk is considered a key discipline by most organisations involved in projects. Best practice project risk management processes are claimed to be self-evidently correct. However, project risk management involves a choice between which information is utilized and which is deemed to be irrelevant and hence excluded. Little research has been carried out to ascertain the manifestation of barriers to optimal project risk management such as ‘irrelevance’; the deliberate inattention of risk actors to risk. This paper presents the results of a qualitative study of IT project managers, investigating their reasons for deeming certain known risks to be irrelevant. The results both confirm and expand on Smithson’s [Smithson, M., 1989. Ignorance and Uncertainty. Springer-Verlag, New York] taxonomy of ignorance and uncertainty and in particular offer further context related insights into the phenomenon of ‘irrelevance’ in project risk management. We suggest that coping with ‘irrelevance’ requires defence mechanisms, the effective management of relevance as well as the setting of, and sticking to priorities.     

ESR Imaging of Conduction Electrons in Organic Conductors

In organic conductors built from stacks of planar aromatic hydrocarbons the mobility of the conduction electrons perpendicular to the radical cation stacks is more than four orders of magnitude smaller than the respective along-the-stack value. Thus the macroscopic properties of real single crystals of such radical cation salts are strongly influenced by the distribution of inevitable defects. Therefore, spatial resolution is required for a meaningful interpretation of the ESR data. Various schemes for 2D and 3D ESR imaging have been realized in the radio frequency and microwave frequency range with a resolution down to 10 m̈m. Spatial distribution of spin density, T₁, T₂, and spin diffusion coefficient D were recorded, often as a function of temperature. The conducting-chain length distribution was observed. Our first attempts for the imaging of the integral and the spatially distributed carrier motion caused by an applied electric current were successful.     

Interactive simulation of one-dimensional flexible parts

In this paper, we present a system for simulating one dimensional flexible parts such as cables or hose. The modelling of bending and torsion follows the Cosserat model. For this purpose we use a generalized spring-mass system and describe its configuration by a carefully chosen set of coordinates. Gravity and contact forces as well as the forces responsible for length conservation are expressed in Cartesian coordinates. But bending and torsion effects can be dealt with more effectively by using quaternions to represent the orientation of the segments joining two neighbouring mass points. This augmented system allows an easy formulation of all interactions with the best appropriate coordinate type and yields a strongly banded Hessian matrix. An energy minimizing process accounts for a solution exempt from the oscillations that are typical of spring-mass systems. The whole system is numerically stable and can be solved at interactive frame rates. It is integrated in a virtual reality software for use in applications such as cable routing and assembly simulation.     

An Overview to the Concept of Smart Coupling and Battery Management for Grid Connected Photovoltaic Battery System

The paper gives an overview on the need for smart coupling for battery management in grid integrated renewable energy system (RES). Grid integrated photovoltaic (PV) battery system, as being popular and extensively used has been discussed in the paper. Smart coupling refers to intelligent grid integration such that it can foresee local network conditions and issue battery power flow management strategy accordingly to shave the peak PV and peak load. Therefore, a need for predictive energy management arises for smart integration to the grid and supervision of the power flow in accordance to the grid conditions. This is also a running project at the Institute of Energy Systems (INES), Offenburg University of Applied Science, Germany since January, 2015. The paper should provide insights to the motivation, need and gives an outlook to the features of desired predictive energy management system (PEMS).     

THE EFFECT OF REGULAR AND IRREGULAR SHEAR LIPS ON FATIGUE CRACK GROWTH IN Al 2024

Abstract— Multiple underloads and overloads with constant Δ K were carried out on centre-cracked tension specimens. It was found that when shear lips develop, underloads or overloads affect the crack growth rate d a /d N and the subsequent retardation. The appearance of the shear lip fracture surfaces depends on the frequency. At higher frequencies a greater number of rough shear lip fracture surfaces will develop, while at lower frequencies there is a tendency towards smooth shear lips. The amount of crack closure differs in each case. It was found that the type of shear lip, rough or smooth, can be related to the effect on d a /d N during and after underloads. The effect of rough and smooth shear lip growth was investigated in constant Δ K tests, performing these tests with and without crack closure.     

Photographic evidence for the third-order rainbow

The first likely photographic observation of the tertiary rainbow caused by sunlight in the open air is reported and analyzed. Whereas primary and secondary rainbows are rather common and easily seen phenomena in atmospheric optics, the tertiary rainbow appears in the sunward side of the sky and is thus largely masked by forward scattered light. Up to now, only a few visual reports and no reliable photographs of the tertiary rainbow are known. Evidence of a third-order rainbow has been obtained by using image processing techniques on a digital photograph that contains no obvious indication of such a rainbow. To rule out any misinterpretation of artifacts, we carefully calibrated the image in order to compare the observed bow's angular position and dispersion with those predicted by theory.     

FACILE SYNTHESIS OF COPPER ANTIMONITE

Copper antimonite, CuSb₂O₄, is a candidate oxidant for use in time delays for mining detonators. A facile process for the synthesis of copper antimonite comprises the reaction of antimony trioxide with copper-ammonia complex with excess ammonia at reflux conditions (ca. 65°C) for about 1 h. Thereafter the reaction is driven to completion by driving off the ammonia by distillation. A well-crystallized product with a cuboid crystal habit approximately 4 µm in size is obtained.