Hybrid Nanovehicles: One Machine,Two Engines

Nanomotors have emerged as promising and versatile nanorobotic tools in a variety of medical, sensing, decontamination, and manufacturing applications due to their unique ability to operate and perform task at small scales. This review focuses on the current progress and future perspectives of hybrid nanomotors based on two power sources, with a special highlight on their distinct advantages, unique propulsion behaviors, adaptive operation, and potential applications. Such incorporation of multiple engines into a single nanoscale vehicle addresses certain limitations of nanomotors based on a single propulsion mode and adds new dimensions for advanced motion management. These attractive capabilities of hybrid nanoscale vehicles are discussed along with the challenges and opportunities when coupling several propulsion modes into a single device. With continuous innovations, it is expected that hybrid nanomotors will have a profound impact upon the field of nanorobotics.     

Fundamental Operation of Rectifiers with Thyristor AC Power Control

The dc output of low-voltage diode rectifiers can be adjusted economically and efficiently by thyristor ac power controllers on the ac side of the rectifier transformer. This method of obtaining voltage control has been used for a number of years. This paper presents an analysis of the various modes of operation, the waveforms, control characteristics, and various other parameters and observations of interest for some commonly employed circuits. In particular the sixpulse bridge rectifier with delta-wye transformer (ASA-23) and the six-pulse double-wye interphase rectifier with delta-double wye transformer (ASA-45) have been studied theoretically as well as experimentally. Attention has been given to the problem of transformer saturation, and the associated requirements for gating accuracy was found to be less stringent than one would expect. It was further discovered that these circuits have some pronounced advantages over the corresponding six-pulse phase controlled converters when comparing dc ripple and reactive power consumption from the line.     

Design and implementation of a new teleoperation control mode for differential drive UGVs

In this paper, we propose and implement a new control mode for teleoperated unmanned ground vehicles (UGVs), that exploits the similarities between computer games and teleoperation robotics. Today, all teleoperated differential drive UGVs use a control mode called Tank Control, in which the UGV chassis and the pan tilt camera are controlled separately. This control mode was also the dominating choice when the computer game genre First Person Shooter (FPS) first appeared. However, the hugely successful FPS genre, including titles such as Doom, Half Life and Call of Duty, now uses a much more intuitive control mode, Free Look Control (FLC), in which rotation and translation of the character are decoupled, and controlled separately. The main contribution of this paper is that we replace Tank Control with FLC in a real UGV. Using feedback linearization, the orientation of the UGV chassis is abstracted away, and the orientation and translation of the camera are decoupled, enabling the operator to use FLC when controlling the UGV. This decoupling is then experimentally verified. The developments in the gaming community indicates that FLC is more intuitive than Tank Control and reduces the well known situational awareness problem. It furthermore reduces the need for operator training, since literary millions of future operators have already spent hundreds of hours using the interface.     

Application of Plasma-Sprayed Complex Perovskites as Thermal Barrier Coatings

In an effort to improve the performance of heat engines at high temperatures, advanced surface coatings have been developed from complex perovskites. Materials of Ba(Mg_1/3Ta_2/3)O₃ and La(Al_1/4Mg_1/2Ta_1/4)O₃ composition were synthesized and applied as ceramic topcoats of thermal barrier coating (TBC) systems by atmospheric plasma spraying (APS) in single layer and in double-layer combination with conventional yttria stabilized zirconia (YSZ). Microstructural and phase analyses reveal that plasma spraying of complex perovskites is accompanied with the formation of vertical crack networks and secondary oxide phases which influence the failure mechanism of the TBCs. The low value of fracture toughness for the complex perovskites and the thermally grown oxide at the topcoat-bondcoat interface of the TBCs are, however, the major factors which lead to the coating failure on thermal cycling at about 1250 °C.     

Pseudospectral method for MHD pipe flow

The paper deals with MHD flow in pipes with arbitrary wall conductivity under the influence of a transverse magnetic field. We employ the pseudospectral collocation method for obtaining a numerical solution of the problem. The numerical results are compared with analytical ones in the case of pipe with insulating walls. We notice that the magnetic field is slowing the motion. Copyright © 2006 John Wiley & Sons, Ltd.     

On the use of a moderation layer to improve the safety behavior in sodium cooled fast reactors

This work shows the effect of the use of moderating layers on the sodium void effect in sodium cooled fast breeder reactors. The moderating layers consisting of either boron carbide B₄C or uranium–zirconium hydride UZrH cause a strong reduction of the sodium void effect. Additionally these layers improve the fuel temperature effect and the coolant effect of the system. The use of the UZrH is significantly more effective for the reduction of the sodium void effect as well as for the improvement of the fuel temperature and the coolant effect. All changes cause by the insertion of the UZrH layer cause a significantly increased stability of the fast reactor system against transients. The moderating layers have only a small influence on the breeding effect and on the production of minor actinides.     

Adaptations for Wear Resistance and Damage Resilience: Micromechanics of Spider Cuticular “Tools”

In the absence of minerals as stiffening agents, insects and spiders often use metal‐ion cross‐linking of protein matrices in their fully organic load‐bearing “tools.” In this comparative study, the hierarchical fiber architecture, elemental distribution, and the micromechanical properties of the manganese‐ and calcium‐rich cuticle of the claws of the spider Cupiennius salei, and the Zn‐rich cuticle of the cheliceral fangs of the same animal are analyzed. By correlating experimental results to finite element analysis, functional microstructural and compositional adaptations are inferred leading to remarkable damage resilience and abrasion tolerance, respectively. The results further reveal that the incorporation of both zinc and manganese/calcium correlates well with increased biomaterial's stiffness and hardness. However, the abrasion‐resistance of the claw material cross‐linked by incorporation of Mn/Ca‐ions surpasses that of many other non‐mineralized biological counterparts and is comparable to that of the fang with more than triple Zn content. These biomaterial‐adaptation paradigms for enhanced wear‐resistance may serve as novel design principles for advanced, high‐performance, functional surfaces, and graded materials.