Safety-monitoring-type wide-range detectable contact sensor system using ultrasonic waves and viscoelastic tubing

In physical human–robot interaction, a contact sensor is fundamentally required for robots to sense contact with humans and to take appropriate safety measures. This paper proposes a wide-range detectable contact sensor system with a safety monitoring function that uses an ultrasonic wave and a silicone rubber tube. The appropriate threshold voltage for generating a monitoring pulse signal is calculated using the estimation equation derived on the basis of the propagation characteristics of ultrasonic waves in straight and curved tubes. By comparing the periodic time between the generated monitoring signals and self-diagnostic signals, the proposed contact detection algorithm detects both contact due to tube deformation and failure of a sensor system including a stack fault. An experiment investigating the relationship between tube deformation by pushing force and the loss of peak voltage of an ultrasonic wave reveals that the sensor system can detect contact when the tube is deformed by 8 mm.     

Simple Salt‐Coordinated n‐Type Nanocarbon Materials Stable in Air

After more than three decades of molecular and carbon‐based electronics, the creation of air‐ and thermally stable n‐type materials remains a challenge in the development of future p/n junction devices such as solar cells and thermoelectric modules. Here a series of ordinary salts are reported such as sodium chloride (NaCl), sodium hydroxide (NaOH), and potassium hydroxide (KOH) with crown ethers as new doping reagents for converting single‐walled carbon nanotubes to stable n‐type materials. Thermoelectric analyses reveal that these new n‐type single‐walled carbon nanotubes display remarkable air stability even at 100 °C for more than 1 month. Their thermoelectric properties with a dimensionless figure‐of‐merit (ZT) of 0.1 make these new n‐type single‐walled carbon nanotubes a most promising candidate for future n‐type carbon‐based thermoelectric materials.     

Characterization and water vapor sorption property of ABA‐type triblock copolymers derived from polyimide and poly(methyl methacrylate)

The characterization of ABA‐type triblock copolymer films derived from polyimide (PI) macroinitiator and poly(methyl methacrylate) (PMMA) synthesized by atom transfer radical polymerization was investigated by focusing on different block lengths of PMMA. The hydrophobic property tends to increase with increasing PMMA content in the triblock copolymers, while the PMMA blocks enhance the charge transfer interaction between the PI segments. The water vapor sorption measurement of triblock copolymers was determined at 35 °C. The water vapor solubility of triblock copolymers tends to decrease with increasing PMMA content. In addition, linear correlations were observed between the solubility and polymer‐free volume and polymer molecular polarity in triblock copolymers as well as in other conventional polymer families. According to Zimm?Lundberg analysis, the PMMA block segments in the triblock copolymers accelerate water vapor clustering due to the high mobility of PMMA. The mobility of PMMA block segments strongly affected not only physical properties but also the water vapor solubility of the triblock copolymers. The ABA triblock copolymerization composed of PI and PMMA is one of the effective ways to improve the hydrophobic property. © 2013 Society of Chemical Industry     

Prediction of the Thickness of a Thin Paint Film by Applying a Modified Partial-Least-Squares-1 Method to Data Obtained in Terahertz Reflectometry

We applied a multivariate analysis method to time-domain (TD) data obtained in terahertz (THz) reflectometry for predicting the thickness of a single-layered paint film deposited on a metal substrate. For prediction purposes, we built a calibration model from TD-THz waveforms obtained from films of different thicknesses but the same kind. Because each TD-THz wave is approximate by the superposition of two echo pulses (one is reflected from the air–film boundary and the other from the film–substrate boundary), a difference in thickness gives a relative peak shift in time in the two echo pulses. Then, we predicted unknown thicknesses of the paint films by using the calibration model. Although any multivariate analysis method can be used, we proposed employing a modified partial-least-squares-1 (PLS1) method because it gives a superior calibration model in principle. The prediction procedure worked well for a moderately thin film (typically, several to several tens of micrometers) rather than a thicker one.     

Nitrogen absorption phenomenon of GTA welding with nitrogen-mixed shielding gases: effect of plasma characteristics on nitrogen content in GTA welded metal

In order to clarify the nitrogen absorption mechanism in gas tungsten arc welding, the measurement of the weld metal nitrogen content under nitrogen mixture shielding gases, and the numerical analysis of plasma heat source characteristics in nitrogen dissociation phenomenon were conducted. The nitrogen content of weld metal produced by He arc reduces to approximately a half relative to that by Ar arc in the shielding gas condition of less than about 1% mixture ratio. Additionally, it is assumed that a decline in the plasma temperature in the vicinity of the molten pools due to the generation of metal vapour, accompanied by a reduction in atom-like nitrogen content, cause intense impact on the reduction mechanism of weld metal nitrogen content in a He arc.     

Examination of a Thermally Viable Structure for an Unconventional Uni-Leg Mg2Si Thermoelectric Power Generator

We have fabricated an unconventional uni-leg structure thermoelectric generator (TEG) element using quad thermoelectric (TE) chips of Sb-doped n-Mg₂Si, which were prepared by a plasma-activated sintering process. The power curve characteristics, the effect of aging up to 500?h, and the thermal gradients at several points on the module were investigated. The observed maximum output power with the heat source at 975?K and the heat sink at 345?K was 341?mW, from which the ??T for the TE chip was calculated to be about 333?K. In aging testing in air ambient, a remarkable feature of the results was that there was no notable change from the initial resistance of the TEG module for as long as 500?h. The thermal distribution for the fabricated uni-leg TEG element was analyzed by finite-element modeling using ANSYS software. To tune the calculation parameters of ANSYS, such as the thermal conductance properties of the corresponding coupled materials in the module, precise measurements of the temperature at various probe points on the module were made. Then, meticulous verification between the measured temperature values and the results calculated by ANSYS was carried out to optimize the parameters.     

Subnanometric stabilization of plasmon-enhanced optical microscopy

We have demonstrated subnanometric stabilization of tip-enhanced optical microscopy under ambient condition. Time-dependent thermal drift of a plasmonic metallic tip was optically sensed at subnanometer scale, and was compensated in real-time. In addition, mechanically induced displacement of the tip, which usually occurs when the amount of tip-applied force varies, was also compensated in situ. The stabilization of tip-enhanced optical microscopy enables us to perform long-time and robust measurement without any degradation of optical signal, resulting in true nanometric optical imaging with high reproducibility and high precision. The technique presented is applicable for AFM-based nanoindentation with subnanometric precision.     

A 400 μm thickness diamond-like carbon preparation

A 400 μm thick diamond-like carbon (DLC) film was prepared on an aluminum alloy (A5052) substrate by a hybrid process of plasma-based ion implantation and deposition using toluene as a precursor gas. The plasma-based ion implantation during deposition relaxed the residual stress in DLC film to almost 0, indicating the production of stress-free DLC. The carbon ion implantation from the methane and acetylene plasmas to the substrate surface, prior to deposition, resulted in an interface graded in carbon composition as well as the formation of amorphous-like structure at the carbon ion-implanted layer that should work as a buffer for stress-relaxation. As a result, a supra-thick DLC film more than 400 μm in thickness was prepared on the substrate.     

A Numerical Simulation of Nanostructure Formation Utilizing Electromigration

A numerical method to simulate nanostructure formation due to electromigration in passivated Al specimens is developed based on the governing parameter for electromigration damage, AFD^*_gen. {\hbox{AFD}}^{\ast}_{\rm gen}. The nanostructure formation is influenced by conditions such as the current density and substrate temperature. The results of the simulations are verified through experiments, and good agreement between the simulations and experiments is found for changes in nanostructure volume. The simulation is expected to be useful for identifying effective conditions for nanostructure formation.     

Influence of Si species on intergrowth and anisotropic crystal growth of silicalite-1

Silicalite-1 crystals were hydrothermally synthesized from silica gels prepared under different conditions. The influence of the state of Si species in the silica gels and the concentrations of silicate ions and a template agent in the reaction sols on crystal growth of silicalite-1 was examined. The use of silica gels with a high degree of condensation of Si species resulted in the intergrowth of silicalite-1 crystals, whereas a low degree of condensation of Si species led to coffin-shaped crystals. Thus, the degree of condensation of Si species had significant influence on the intergrowth of silicalite-1 crystals. Moreover, at a low silicate concentration, silicalite-1 crystals elongated along the c-axis were obtained. With increasing silicate concentration in the reaction sols, the aspect ratio of silicalite-1 decreased. Furthermore, with decreasing the amount of N(C₃H₇) ₄ ⁺ used as a template agent, the silicalite-1 crystals became larger isotropically. Thus, the growth direction of silicalite-1 crystals was dependent on silicate ion concentration in the reaction sols, but not on N(C₃H₇) ₄ ⁺ concentration.