Influence of ion bombardment on the properties and microstructure of unbalanced magnetron deposited niobium coatings

The effect of the ion bombardment to unbalanced magnetron deposited, approximately 1.5 and 4.5 μm thick, Nb coatings have been investigated as the bias voltage was varied from U_B=−75 to −150 V. Increasing bias voltage increased the hardness of the coating from 4.5 to 8.0 GPa. This was associated with residual stress and Ar incorporation into the Nb lattice. Strong {110} texture developed in the samples deposited at low bias voltages, while beyond U_B=−100 V a {111} texture became dominant. However, strong {111} texture was observed only with the thicker 3Nb coatings. Secondary electron microscopy investigation of the coating topography showed fewer defects in the thicker coatings. All coatings exhibited good corrosion resistance, with the thicker coatings clearly outperforming the thinner ones. Excessive bias voltages (U_B=−150 V) was found to lead to poor adhesion and loss of corrosion resistance.     

Least privilege and more [computer security]

With new methods for enforcing security policies comes the opportunity to formulate application-specific policies. But leveraging that flexibility might prove a difficult problem, not only in practice, but also in theory.     

Terahertz characterisation of building materials

To obtain realistic models for propagation channels in future pico-cellular indoor terahertz communication systems it is necessary to know the reflective properties of building materials found in a typical office environment. The angular dependent reflection coefficients of different building materials were determined using terahertz time-domain spectroscopy in transmission geometry and Fresnel's equations. This approach is more efficient than a set of measurements in reflection geometry for different angles. Verification of the method with a set of such reflection measurements shows an excellent agreement.     

Efficient manipulator collision avoidance by dynamic programming

This paper describes a research effort in the area of collision avoidance path planning for robotic manipulators. A robotic arm with known geometry is to perform a spatial manipulation in the presence of known obstacles in its workspace. The task is to generate a series of waypoints for its path to pass through which will guarantee a safe, collision-free trajectory from its predefined starting point to its predefined goal position.This is an important topic in the area of automated manufacturing. Automated factories are becoming increasingly important for the goals of greater manufacturing efficiency, better equipment utilization, and lower overall manufacturing costs. Robotic devices, including manipulator arms and assembly devices, are finding more uses in these factories.The approach is to discretize the robot's workspace into a transition network. The optimal path through this network, in terms of angular displacement of the manipulator's joints, is generated by dynamic programming. While this approach has been used previously, this paper adds the innovation of variable-node spacing, with the node density in various parts of the network reflecting the need for precise position control in each local area of the workspace. In this way, precise motion control is possible without an undue computational burden.     

Cinematic primitives for multimedia

The development of robust frameworks in interactive multimedia for representing story elements to the machine so that they can be retrieved in multiple contexts is addressed. Interactive multimedia is discussed as a user-directed form of storytelling, and the nature of cinematic storytelling is examined. It is proposed that content can be represented in layers. This model for layered information will allow programs to take advantage of the relation between cinematic sequences and the world they represent. The collection of content by the camera and microphone is considered in this context. The use of the methodology to build meaningful, context-rich sequences is discussed     

A cathode readout gas sampling calorimeter with conductive plastic tubes

We constructed and tested a prototype gas sampling electromagnetic calorimeter of the Pb-proportional tube sandwich type. The calorimeter uses conductive plastic tubes and cathode pad readout with a tower structure which resulted in reasonable energy and spatial resolutions for electrons in the momentum range 0.5–4.0 GeV/c; $\text{σ}{}_{\mathrm{E}}\text{E =}\text{21\%}\text{(E(}\text{GeV}\text{)}\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{, σ}{}_{\mathrm{x}}\text{= 6}\text{mm}\text{(at 3 GeV}$/c). This paper describes the test and the performance studied under various conditions.     

Fabrication of a poly-Si thin-film transistor with storage capacitor

The fabrication process of a low-temperature poly-Si thin-film transistor (TFT) with a storage capacitor was studied. The atmospheric-pressure chemical-vapour deposited SiO₂ protected the buried indium tin oxide (ITO) from reduction by a pure H₂ plasma treatment that was essential for the effective improvement of the poly-Si TFT characteristics. Thus, a storage capacitor with an ITO (picture electrode)-SiO₂-ITO (buried common electrode) structure was successfully fabricated. The poly-Si TFT with a channel width/length W/L ratio of 5 drove a 3 pF storage capacitor in 2 μs, and it showed superior driverability for LCD use. The TFT also had good hold characteristics under illumination for the realization of grey-scale representation.     

On mass transfer effect due to electrolytically evolved gas

Based on the Ibl penetration model mass transfer equations for gas-evolving electrodes were derived and compared to the effect of forced convection. Experimental studies were conducted in a rectangular flow channel with the working electrode facing downward. The variables were linear bubble velocity, linear electrolyte velocity, nature of the gas and electrode position. Up to bubble velocities (U_x) of 2 and 6 cm s⁻¹ for O₂ and H₂ gases respectively, the thickness of the Nernst diffusion layer (δ_av) was described well by the equation δ_av = [Dd_eL/(U_x)_av]^1/3. Intermediate slopes between − 1/3 and − 1 were observed for O₂ bubble velocities between 2 and 6 cm s⁻¹. A theoretical derivation suggests that in the absence of bubble coalescence, the mass transfer effect due to laminar flow induced by electrolytically evolved gas exceeds that due to forced external laminar flow for all practical channel designs.     

Metalloporphyrins in Oxidative Catalysis. Oxygen Transfer Reactions of Oxochromium Porphyrins

The oxidation of chloro-5-10,15,20-tetramesitylporphyrinotoiron(III) with peroxyacids affords a reactive oxoiron(IV)-porphyrin cation radical species 2. The characterization of 2 and its oxochromium analogs 3, 4 and 5 are reviewed. The nature of reactive oxochromium species derived from chromyl reagents is also reviewed. The oxidation of triphenylphosphine by CrOTPP (11), CrOTTP (13) and CrOTMP (14) is described. Variations in the rate constants indicate that steric factors affect the rate of oxygen atom transfer. Activation parameters for the oxidation of triphenylphosphine by 14 are ΔH^≠ = 6.96 kcal/mol and ΔS^≠ = −39 eu. The oxidation of t-butylphenylcarbinol (18) by CrOTPP gave predominantly benzaldehyde via carbon—carbon bond cleavage while the chromium(III) porphyrin-catalyzed oxidation of 18 by iodosylbenzene afforded t-butylphenylketone.