Effect of heat treatment on the efficiency of Mg anodes

Commercial magnesium anodes were evaluated using ASTM G 97-89 for a standard test along with a technique of electrochemical impedance. Several heat treatments were performed, and the anodic efficiency was determined, showing an incremental increase of 10 to 12 % of the efficiency demonstrated by the nontreated commercial anodes (as-cast condition). The increase in efficiency was related to the microstructural characteristics. The appearance of second phase particles influenced the form of the corrosion process.     

A bio-inspired predictive sensory-motor coordination scheme for robot reaching and preshaping

This paper presents a sensory-motor coordination scheme for a robot hand-arm-head system that provides the robot with the capability to reach an object while pre-shaping the fingers to the required grasp configuration and while predicting the tactile image that will be perceived after grasping. A model for sensory-motor coordination derived from studies in humans inspired the development of this scheme. A peculiar feature of this model is the prediction of the tactile image. The implementation of the proposed scheme is based on a neuro-fuzzy module that, after a learning phase, starting from visual data, calculates the position and orientation of the hand for reaching, selects the best-suited hand configuration, and predicts the tactile feedback. The implementation of the scheme on a humanoid robot allowed experimental validation of its effectiveness in robotics and provided perspectives on applications of sensory predictions in robot motor control.     

FT²EI: A Dynamic Fault-Tolerant Routing Methodology for Fat Trees with Exclusion Intervals

Fault tolerance in the interconnection network of large clusters of PCs is an issue of growing importance, since their increasing size also increases the failure probability. The fat-tree topology is usually used in these machines since it has become very popular among high-speed interconnect manufacturers. This paper proposes a new distributed fault-tolerant routing methodology for fat trees. Unlike other previous proposals, it does not require additional network hardware, and its memory requirements, switch hardware, and routing delay scales up with the network size. Indeed, it nullifies only the strictly necessary paths, allowing adaptive routing through the healthy paths. The methodology is based on enhancing the interval routing scheme with exclusion intervals. Exclusion intervals are associated to each switch output port and represent the nodes that are unreachable from this port after a fault. We propose a methodology to identify the links where the exclusion intervals must be updated after a fault, the values to write on them, and a very efficient mechanism to distribute the required information through the network without stopping the system activity. Our methodology can tolerate a high number of network failures with a low degradation in performance. Moreover, it can achieve zero packet losing during the updating period.     

Boosting the confidence of new product development teams: The role of team boundary spanning,team size and functional diversity

In today's highly interconnected, uncertain and dynamic business environment, team boundary spanning has become an important determinant of the performance of new product development (NPD) projects. Despite the positive evidence supporting the use of boundary spanning activities by NPD teams, little is still known about how boundary spanning teams become high-performance teams. The current study advances research on this subject by examining the mediating effect of team potency on the relationship between team boundary spanning and new product performance, as well as the moderating effects of team size and functional diversity on the relationship between team boundary spanning and team potency. Data from a time-lagged survey study of 140 NPD projects found that team boundary spanning can promote team potency that, in turn, results in greater new product quality and new product creativity. The positive effect of team boundary spanning on team potency was found to be more pronounced for NPD teams of medium size and high levels of functional diversity.     

Effects of Environmental Oxygen Content and Dissolved Oxygen on the Surface Tension and Viscosity of Liquid Nickel

The NASA Marshall Space Flight Center’s electrostatic levitation (ESL) laboratory has recently added an oxygen partial pressure controller. This system allows the oxygen partial pressure within the vacuum chamber to be measured and controlled in the range from approximately \(10^{-28}\,{\mathrm {to}}\,10^{-9}\) bar, while in a vacuum atmosphere. The oxygen control system installed in the ESL laboratory’s main chamber consists of an oxygen sensor, oxygen pump, and a control unit. The sensor is a potentiometric device that determines the difference in oxygen activity in two gas compartments (inside the chamber and the air outside of the chamber) separated by an electrolyte. The pump utilizes coulometric titration to either add or remove oxygen. The system is controlled by a desktop control unit, which can also be accessed via a computer. The controller performs temperature control for the sensor and pump, has a PID-based current loop and a control algorithm. Oxygen partial pressure has been shown to play a significant role in the surface tension of liquid metals. Oxide films or dissolved oxygen may lead to significant changes in surface tension. The effects on surface tension and viscosity by oxygen partial pressure in the surrounding environment and the melt dissolved oxygen content will be evaluated, and the results will be presented. The surface tension and viscosity will be measured at several different oxygen partial pressures while the sample is undercooled. Surface tension and viscosity will be measured using the oscillating droplet method.     

Ultra-dense planar metallic nanowire arrays with extremely large anisotropic optical and magnetic properties

A nanofabrication method for the production of ultra-dense planar metallic nanowire arrays scalable to wafer-size is presented. The method is based on an efficient template deposition process to grow diverse metallic nanowire arrays with extreme regularity in only two steps. First, III–V semiconductor substrates are irradiated by a low-energy ion beam at an elevated temperature, forming a highly ordered nanogroove pattern by a “reverse epitaxy” process due to self-assembly of surface vacancies. Second, diverse metallic nanowire arrays (Au, Fe, Ni, Co, FeAl alloy) are fabricated on these III–V templates by deposition at a glancing incidence angle. This method allows for the fabrication of metallic nanowire arrays with periodicities down to 45 nm scaled up to wafer-size fabrication. As typical noble and magnetic metals, the Au and Fe nanowire arrays produced here exhibited large anisotropic optical and magnetic properties, respectively. The excitation of localized surface plasmon resonances (LSPRs) of the Au nanowire arrays resulted in a high electric field enhancement, which was used to detect phthalocyanine (CoPc) in surface-enhanced Raman scattering (SERS). Furthermore, the Fe nanowire arrays showed a very high in-plane magnetic anisotropy of approximately 412 mT, which may be the largest in-plane magnetic anisotropy field yet reported that is solely induced via shape anisotropy within the plane of a thin film.

Open image in new window

     

Cyclic Nanoindentation for Local High Cycle Fatigue Investigations: A Methodological Approach Accounting for Thermal Drift

Cyclic nanoindentation allows characterizing the influence of single phases and their interactions on fatigue mechanisms. Herein, a method for high cycle fatigue testing by nanoindentation is presented. By combining high- and low-frequency indentation modes, high cycle numbers are achieved while obtaining sufficient data points to reconstruct force–displacement hysteresis loops. A challenge is the stochastic course of thermal drift which is addressed by measuring drift rate in regular low-force holding segments. Drift rates are used to correct the displacement values, yielding reproducible cyclic deformation data as it is shown for two very different materials, a ductile metal and a brittle ceramic.