Wear Resistance of Coatings from Self‐Fluxing Alloys after Laser Doping under Dry Friction Conditions

The wear resistance of Ni–Cr–B–Si–C coatings after laser treatment with a doping covering under dry friction conditions has been investigated. The microstructure of coatings after fusion by a gas burner and a laser beam and the roughness and waviness parameters of the friction surfaces before and after wear have been investigated.     

On certain classes of exact solutions of Einstein equations for rotating fields in conventional and nonconventional form

Using the symmetry reduction approach we have herein examined, under continuous groups of transformations, the invariance of Einstein exterior equations for stationary axisymmetric and rotating case, in conventional and nonconventional forms, that is a coupled system of nonlinear partial differential equations of second order. More specifically, the said technique yields the invariant transformation that reduces the given system of partial differential equations to a system of nonlinear ordinary differential equations (nlodes) which, in the case of conventional form, is reduced to a single nlode of second order. The first integral of the resulting nlode has been obtained via invariant-variational principle and Noether’s theorem and involves an integration constant. Depending upon the choice of the arbitrary constant two different forms of the exact solutions are indicated. The generalized forms of Weyl and Schwarzschild solutions for the case of no spin have also been deduced as particular cases. Investigation of nonconventional form of Einstein exterior equations has not only led to the recovery of solutions obtained through conventional form but it also yields physically important asymptotically flat solutions. In a particular case, a single third order nlode has been derived which evidently opens up the possibility of finding many further interesting solutions of the exterior field equations.     

Tunneling recombination in spatially inhomogeneous structures

Methods for finding the parameters (energies and capture coefficients for electrons and holes) of the levels involved in the formation of the recombination flux are suggested. The temperature variation of these parameters for AlGaN/InGaN/GaN and InGaN/SiC structures is discussed. The parameters of the levels responsible for tunneling recombination are determined.     

Automatic transport plane resource discovery mechanisms for ASON/GMPLS ring networks

In this letter, we propose two novel mechanisms which enable GMPLS LMP to cope with the automatic discovery of all-optical transport planes. The feasibility of our contributions and their performances are assessed by simulations as well as experimental results over the ASON/GMPLS CARISMA field-trial     

Closed-loop optimal control-enabled piezoelectric microforce sensors

This paper presents a closed-loop optimally controlled force-sensing technology with applications in both micromanipulation and microassembly. The microforce-sensing technology in this paper is based on a cantilevered composite beam structure with embedded piezoelectric polyvinylidene fluoride (PVDF) actuating and sensing layers. In this type of sensor, the application of an external load causes deformation within the PVDF sensing layer. This generates a signal that is fed through a linear quadratic regulator (LQR) optimal servoed controller to the PVDF actuating layer. This in turn generates a balancing force to counteract the externally applied load. As a result, a closed feedback loop is formed, which causes the tip of this highly sensitive sensor to remain in its equilibrium position, even in the presence of dynamically applied external loads. The sensor's stiffness is virtually improved as a result of the equilibrium position whenever the control loop is active, thereby enabling accurate motion control of the sensor tip for fine micromanipulation and microassembly. Furthermore, the applied force can be determined in real time through measurement of the balance force.     

Pin&Play: the surface as network medium

Integrating appliances in the home through a wired network often proves to be impractical: routing cables is usually difficult, changing the network structure afterward even more so, and portable devices can only be connected at fixed connection points. Wireless networks are not the answer either: batteries have to be regularly replaced or changed, and what they add to the device's size and weight might be disproportionate for smaller appliances. In Pin&Play, we explore a design space in between typical wired and wireless networks, investigating the use of surfaces to network objects that are attached to it. This article gives an overview of the network model, and describes functioning prototypes that were built as a proof of concept.     

Effect of Organic Additives on Electrochemical Surface Precipitation and Polymorphism of CaCO3

The inhibition effect of three organic additives on the precipitation and polymorphism of CaCO₃ deposited on gold surfaces was investigated using electrochemical and microscopic techniques. Additives, two polyacrylic acid (PAA) polymers with different molecular weights (Mw 2100, Mw 30,000), and 1,2,4,5‐benzenetetracarboxylic acid (BTCA), were either added to the solution before or during deposition. In the presence of 100 ppm of one of the three additives in solution, almost no scale was observed on the surface for at least 24 hours. In the presence of lower concentrations of PAA Mw 2100, only distorted calcite crystals were obtained while with PAA Mw 30,000 the polymorph was spherical vaterite. A mixture of calcite and vaterite was observed with the BTCA additive. Addition of the polymers inhibits further nucleation and growth even if added after partial deposition of CaCO₃ while BTCA has no effect once nucleation has started. The results indicate that the inhibit ion effect of the PAA polymers is due to adsorption on the electrode surface while the effect of BTCA is related to chelation of calcium ions in solution.     

Successful Aging

This issue's Works in Progress department presents six abstracts for projects that are developing interesting solutions to the elderly's quality of life challenges. The first two abstracts discuss projects that will help provide the elderly with freedom and independence by instrumenting their environments with supportive technology. The next two abstracts discuss projects building specialized user interfaces for addressing some of the challenges associated with aging, such as vision impairment. The final two abstracts present projects that will aid independence for the elderly by providing remote monitoring and assistance.     

Direct gravure printing (DGP) method for printing fine-line electrical circuits on ceramics

The tendency toward higher packing densities and higher frequencies for telecommunication devices based on ceramic technology requires smaller dimensions for electrical wiring. Electrical thick-film circuits for ceramic and LTCC-substrates have, up to now, been printed with screen printing, where the printing lines width limit is about 125 /spl mu/m in mass production. A silicone polymer direct gravure printing (Si-DGP) process has been developed to perform smaller dimensions, down to 20 /spl mu/m lines width, for electrical circuitry. In the DGP process, the conductor paste is doctored to the grooves of the gravure and then it is pressed against the substrate. The paste is, thus, printed directly onto the substrate from the patterned gravure. The results showed that, using the DGP process, it was possible to print conductor lines down to 20 /spl mu/m in width. It was also noted that a 100% transfer of paste from the grooves of the gravure could be obtained with commercial pastes using the silicone polymer gravure. A dried thickness of up to 28 /spl mu/m was measured for the narrowest lines. Also conductor lines printed by the Si-DGP method were embedded inside LTCC-module.