Teleoperated touch feedback from the surfaces at the nanoscale: modeling and experiments

In this paper, a teleoperated nanoscale touching system is proposed, and continuum nanoscale contact mechanics models are introduced. The tele-nanorobotic system consists of a piezoresistive nanoprobe with a sharp tip as the nanorobot and force-topology sensor, a custom-made 1-degree-of-freedom haptic device for force-feedback, three-dimensional (3D) virtual reality (VR) graphics display of the nano world for visual feedback, and a force-reflecting servo type scaled teleoperation controller. Using this system, one-dimensional and 3D touching experiments and VR simulations are realized. Scaling of nano-forces is one of the major issues of the scaled teleoperation system since nanometer scale forces are dominated by surface forces instead of inertial forces as in the macro world. As the force scaling approach, a heuristic rule is introduced where nano-forces are linearly scaled with an experimentally determined scaling parameter. Simulation results and preliminary experiments of touching silicon and InAs quantum dot nanostructures show that adhesion forces at the nanoscale can be felt repeatedly at the operator's hand, and the proposed system enables the nanoscale surface topography and contact/noncontact nano-force feedback.     

Temperature dependence of electrical conductivity in double-wall and multi-wall carbon nanotube/polyester nanocomposites

The aim of this study is to investigate temperature dependence of electrical conductivity of carbon nanotube (CNT)/polyester nanocomposites from room temperature to 77 K using four-point probe test method. To produce nanocomposites, various types and amounts of CNTs (0.1, 0.3 and 0.5 wt.%) were dispersed via 3-roll mill technique within a specially formulized resin blend of thermoset polyesters. CNTs used in the study include multi walled carbon nanotubes (MWCNT) and double-walled carbon nanotubes (DWCNT) with and without amine functional groups (–NH₂). It was observed that the incorporation of carbon nanotubes into resin blend yields electrically percolating networks and electrical conductivity of the resulting nanocomposites increases with increasing amount of nanotubes. However, nanocomposites containing amino functionalized carbon nanotubes exhibit relatively lower electrical conductivity compared to those with non-functionalized carbon nanotubes. To get better interpretation of the mechanism leading to conductive network via CNTs with and without amine functional groups, the experimental results were fitted to fluctuation-induced tunneling through the barriers between the metallic regions model. It was found that the results are in good agreement with prediction of proposed model.     

Solutions to multiphase diffusion in binary metal interstitial systems

General analytical expressions for multiphase diffusion under nonsteady-state conditions, which treats the special degenerative case of steady-state diffusion, are developed. The validity of these solutions is examined by application to multiphase layer growth in the Zr-0 and Fe-N systems. The analytical solutions examined include closed-form error function solutions and steady-state approximations to the solutions developed by Wagner. The solutions are general and can accommodate solubility ranges in all phase layers as well as terminal solubilities in the end member phases of the diffusion couple. In diffusion couples where the end member phases have finite, terminal solubilities and where these terminal phases have diffusivities greater than in the intermediate phases (which is common in many metal-interstitial phases), closed-form error function solutions are particularly useful in determining chemical diffusivities from simple intermediate phase layer growth measurements.     

A Computer Aided Investigation on Strain Movements in Compacts Under Constant Stress Within the Die

A 2.54cm diameter punch and die set has been used in conjunction with a Mayes Hydraulic Machine to examine strain movements within the die of compacts maintained at constant stress. These were prepared from the bases Avicel PH 101 (AV), Sta-Rx 1500 (ST), Paracetamol DC (PC), Emdex (ED) and Eacompress (EC).

Compression force and punch movements were simultaneously monitored using a CBM nicroconputer with disk storage of data.

All compacts showed time dependent consolidation under constar. stress when held at 'holding time' of up to 60s. PC, AV and ST exhibited comparable movements but that of ED and EC ware less.

Elastic recovery on sudden release of load was followed using machine code logging over a period of 90ms. Large recoveries were recorded for AV, PC and ST. If load release was immediate (zero holding time) then the recovery was greater when compared with recovery after holding tines of 30 and 60s, suggesting that some elastic energy was dissipated during the holding time. Elastic recovery of ED and EC was about half that of the other bases. Although these bases also showed reduced recovery with holding tine, percentage reduction was smaller than for the other bases.

Following elastic recovery, a much slower viscoelastic movement could be demonstrated. It was difficult to clearly demarcate the division between viscoelastic and elastic movement but it appeared that the movement on viscoelastic consolidation was comparable to that en recovery when the load was removed.

There are many references to tine dependent effects during tablet compression to be found in the literature. One of the earliest was due to Rees and Shotton (1) who found that the crushing strength of sodium chloride tablets could double after the lapse of one hour from ejection. This has recently been shown by Rue and Barkworth (2) to be due to the existence of a work hardened outer shell which inhibits relaxation by viscoelastic flow.

Several authors (3,4,5) have investigated the stress decay that occurs when a tablet is held at a nominally constant force. Thus Wells and Langridge (5) monitored the fall from a peak pressure of 332MN/m²on a tablet prepared in a single punch machine turned by hand. Similar techniques have been described by Rees and Rue (3), Kiestand and others (4) and Shlanta and Milosovich (6). However as Rees and Rue have pointed out, these methods measure stress relaxation under constant strain conditions. Their results and conclusions differed from those of David and Augsburger (7) who compressed the same direct compression bases on a rotary tablet machine. In a rotary machine compression takes place under virtually constant, stress conditions because of the buffer effect of the powerful springs fitted to the compression wheels.

This paper describes some techniques and observations on the compression of some direct compression bases using a Mayes Hydraulic Testing Machine (WH Mayes (Windsor) Ltd) which is capable of maintaining constant stress conditions on a compact formed in a punch and die set mounted between the platens.     

Thermoluminescence properties of irradiated chickpea and corn

A study was carried out to establish a detection method for irradiated chickpea and corn by thermoluminescence (TL) method. The leguminous were packed in polyethylene bags and then the packets were irradiated at room temperature at different doses by ⁶⁰Co gamma source at 1, 4, 8 and 10 kGy. Minerals extracted from the leguminous were deposited onto a clean aluminum disc and TL intensities of the minerals were measured by TL. It was observed that the extracted samples from both leguminous exhibit good TL Intensity and the TL intensity of glow curves of them increased proportionally to irradiation doses. The TL glow curve of both irradiated leguminous presents a single broad peak below 400 °C. The TL trapping parameters glow peaks were estimated by the additive dose (AD), T_m(E_a)-T_stop and computerized glow curve deconvolution (CGCD) methods. The fading characteristics of glow curves were also recorded up to 6 months.     

Effect of α- and γ-alumina on the precipitation of positive electrolyte in vanadium redox battery

In this study, the effect of α-alumina (α-Al₂O₃) and γ-alumina (γ-Al₂O₃) on the precipitation of the positive electrolyte, which is one of the most important problems in vanadium redox battery (VRB) systems, was investigated. α-Al₂O₃ and γ-Al₂O₃ were used as additive materials to improve the thermal stability of V(V) ion and the performance of VRB at high temperatures. Cyclic voltammetry and electrochemical impedance spectroscopy were used to determine the properties of positive electrolyte systems. The optimum amount of additives was identified as wt% 0.004 and 0.010 for α-Al₂O₃ and γ-Al₂O₃, respectively. The surface morphology and composition of electrodes were investigated by scanning electron microscopy and energy-dispersive X-ray analysis. A plausible reaction mechanism was also proposed for redox reaction occurring on the positive electrode of a VRB. The adsorption of V(V) ions to the electrode surface from the solution increased by the time additives were added into the system. γ-Al₂O₃ showed the best anti-precipitation effects for the V(V) ion at 40 °C and 60 °C in the precipitation tests. In the battery test, the discharge capacity of γ-Al₂O₃ with a positive electrolyte, was the highest at 87.2 mAh. According to thermal and electrochemical studies, γ-Al₂O₃ can be a useful additive for the positive electrolyte of a VRB.     

Vibration analysis of symmetric laminated composite plates with attached mass

In this study, vibration of symmetrically laminated composite plates with attached mass is studied. The Ritz method with algebraic polynomial displacement field is used. The plates with at least two adjacent free edges are considered in the formulations. The effect of various parameters (number of layers, ratio of attached mass to the plate mass, position of attached mass, fiber orientation) upon the frequencies and mode shapes is investigated. It is found that attachment of a mass has important effects on the vibration characteristics of composite laminated plates.     

Effect of pre-setting pressure applied to mechanical behaviours of reactive powder concrete during setting phase

In this study, mixing rates, fiber content and pre-setting pressure of reactive powder concrete (RPC) were examined. Mixing ratios were determined by different mixing techniques in literature using material characteristics via computer software. The samples were prepared according to these mixing ratios. The fresh (plastic) concrete samples were filled in a specified mould. Six different (0, 5, 10, 15, 20, 25 MPa) pre-setting pressure were applied. It is observed that application of pre-setting pressure increased compressive strength of the samples about twice.     

PSAR: power-source-aware routing in ZigBee networks

ZigBee is a recent wireless networking technology built on IEEE 802.15.4 standard and designed especially for low-data rate and low-duty cycle applications such as home and building automation and sensor networks. One of the primary goals of ZigBee is low power consumption and therefore long-living networks. Despite this goal, current network formation and routing protocols described in the ZigBee specification do not fully address power consumption issues. In this work, we propose a distributed routing algorithm to reduce power consumption of battery-powered devices by routing the communication through mains-powered devices whenever possible and consequently increasing the overall network lifetime. The proposed algorithm works on tree topologies supported by ZigBee and requires only minor modifications to the current specification. Our ns-2 simulation results showed that the algorithm is able to reduce the power consumption of battery-powered devices significantly with minimal communication overhead.